Data binding
All three objects can be used as data sources of data binding controls. DataSet and DataTable can be used as data sources for wider range controls. This is because DataSet and DataTable implementation (generating ILIST interface) IListSource interface, and SqlDataReader implements the Ienumerable interface. Many WinForm controls that can perform data binding needs to implement the data source of the ILIST interface.
This difference is because the type of scene designed for each object type is different. DataSet is a rich, non-linked structure that is suitable for web and desktop applications. On the other hand, the data reader has been optimized for web applications. This application needs to be optimized and can only access forward.
Check the data source requirements for the specific control type to be bound.
Pass data between application layers
DataSet provides a diagram that can be used as an XML arbitrarily manipulated data, and non-link cache copies that allow data is delivered between application layers and components. However, SQLDataReader provides more optimized performance because it avoids performance and memory overhead associated with creating DataSet. Remember, DataSet objects will result in multiple sub-objects - including DataTable, DataRow, and Datacolumn - and as a collection object of these sub-object containers.
Use dataset
DataSet objects filled with SqlDataAdapter when:
You need a non-linking cache data for cache data so that you can pass it to other layers in other components or applications. You need a data relationship diagram in memory to perform XML or non-XML operations. The data you are using is from multiple data sources, such as multiple databases, tables, or files. You want to update some or all rows, and hope to use the batch of SqlDataAdapter. You have to bind data to the control, and this control requires support for the ILIST interface.
More information
If you use SqlDataAdapter to generate DataSet or DataTable, you should pay attention to:
You don't have to clearly open or close the database link. The SQLDataAdapter Fill method opens the database link and turn it off before this method returns. If the link has been turned on, this method still makes the links open. If you need link for other purposes, consider opening the link before calling the Fill method. This way you can avoid unnecessary open / closing operations, improve performance. Although the same SQLCommand object can be repeatedly executed, do not repeat the use of this object to perform different commands. For how to use the SqlDataAdapter object to populate the code example of the DataSet or DataTable object, see how to use the SqlDataAdapter object in the appendix.
Use SqldataReader
Some inferior conditions, you can use the SqlDataReader object obtained by calling the ExecuteReader method of the SQLCommand object:
When processing a lot of data - too much, it cannot be maintained in a single buffer. I hope to reduce the imprint of the application in memory. I hope to avoid creating related overhead with the DataSet object. I want to perform data binding operations for a control, and this control supports the data source of the IEnumerable interface. I hope the streamlined data access and optimize it. A row that contains the binary large object (blob) is read. You can use the SqlDataReader object to pull the BLOB data from the database from the database in a manageable large block, rather than one-time extraction. For more details on processing BLOB data, see this article handling blobs
one period.
More information
If you use the SqlDataReader object, please note:
During the data reader activity, the underlying database link is kept open and cannot be used for any other purpose. Call the CLOSE method as possible in the place of the SQLDataReader object. Each link can only have a data reader. By passing the COMMANDBEHAVIOR.CloseConnection enumeration value to the ExecuteReader method, you can clear the link after using the data reader; or bind the link lifecycle to the SqlDataReader object. This indicates that the link will also turn off when the SqlDataReader object is turned off. When using the reader access data, if you know the underlying data type of the column, you should use the type of accessor method (such as getInt32 and getString) because these methods reduce reading when reading column data. The amount of type conversion required for column data. To avoid sending unnecessary data from the server to the client, if you want to close the reader and discard all the results of all reserved results, call the CANCEL method to call the command object before calling the Close method to the reader. The CANCEL method ensures that the result of the server is abandoned without being sent to the client. Instead, the CLOSE method to call the data reader will make the reader unnecessarily extract the result of the reserved result to empty the data stream. If you want to get the output value or return value returned from the stored procedure, and you can call the Close method to the reader before you get the output or return value, you must call the reader before getting the output or return value. About demonstrating how to use the SQLDataReader object, how to use the SqlDataReader object to get multi-line data in the appendix. Use XMLReader
In the following cases, the XMLReader object obtained by calling the EXECUTEXMLReader method of the SQLCommand object:
It is desirable to process the data as an XML, but do not want to trigger additional performance overhead due to the creation of a DataSet object, and the non-link cache of the data is not required. It is desirable to use the SQL Server for XML syntax, which allows for a flexible way to get an XML fragment from the database (ie, an XML document without root elements). For example, this approach allows you to accurately specify the element name, is the use element or a graphic of the attribute as the core, the illustration is returned with XML data, and so on.
More information
If you use XmlReader, please note:
The link must remain open when reading data from the XMLReader object. The ExecutexmlReader method of the SQLCommand object does not currently supports the Commandbehavior.CloseConnection enumeration value, so the link must be clearly closed after the reader is used. For how to use the code example of the XMLReader object, see how multi-line data is obtained using XmlReader in the appendix.
Get a single line of data
In this scenario, a single line of data containing a set of specified columns will be obtained from the data source. For example, you get a customer ID and want to find details related to the customer; or get a product ID, and hope to get product information.
Method comparison
If you want to perform a binding operation from a line of data obtained from the data source, you can populate the DataSet or DataTable object with the SqlDataAdapter object, which is the same as the method described in the previously discussed multi-line data and repeating scenarios. However, this object should be avoided unless otherwise requiring a DataSet or DataTable object.
If you need to get a single line of data, use one of the following methods:
Use stored procedure output parameters. Use the SqlDataReader object.
Both methods avoid unnecessary additional overhead of the server-side creation result set and create a DataSet object in the client. The relative performance of each method relies on whether the intensity level and whether the database link is enabled. When the database link is enabled, the performance test indicates that the stored procedure method is similar to the SqlDataReader method in the high-intensity environment (more than 200 links at the same time). Use stored procedure output parameters
Use stored procedure output parameters in the following cases:
To get a row of data from a linked poolization enabled multi-layer web application.
More information
Regarding the code example of how to use the stored procedure output parameter, see the use of stored procedure output parameters in the appendix to obtain a row of data.
Use the SqlDataReader object
The following conditions are required to use the SqlDataReader object:
In addition to data values, metadata is required. The column metadata can be obtained using the GetSchematable method of the data reader. Did not use a link poolization. When link pool is invalid, the SqlDataReader object is a good way in all intensity environments; performance tests indicate that this method is approximately 20% higher than storage process methods when the 200 browser link is linked.
More information
If you know that the query results need to return a line, use the commandbehavior.singlerow enumeration value when calling the SQLCOMMAND object method. Some suppliers such as OLE DB .NET data supplies, use this skill to optimize performance. For example, the supplier uses an IROW interface (if this interface exists) instead of a higher IROWSET interface. This parameter has no effect on the SQL Server .NET data supplier. When using the SqlDataReader object, the output parameters should always be used through the type of Accessor of the SqlDataReader object, such as getString and GetDecimal. This avoids unnecessary type conversion. With regard to how to use the SqlDataReader object to get a single line of code, see How to use the SqlDataReader object in the appendix to get a single line of data.
Get single data
In this scenario, you have to get a single data. For example, after the product ID is provided, you want to query a single product name; or give the customer name, you want to query the customer's credit rating. In this scenario, in order to obtain single data, it is usually not desirable to raise additional overhead created a DataSet object or even a DataTable object.
Maybe just want to check if there is a specific row in the database. For example, when the new user registers on the website, you need to check if the selected username already exists. This is a very special example in a single data query, but in this example, it is enough to return a simple Boolean return value.
Method comparison
When obtaining a single data from the data source, consider the following method:
The ExecuteScalar method for the SQLCommand object with the memory process. Use stored procedures to output or return to parameters. Use the SqlDataReader object.
The ExecuteScalar method returns the data item directly because it is designed to return only a single value, which requires less code compared to the stored procedure output parameters and the SqlDataReader method.
In terms of performance, the stored procedure output or return parameters should be used because the test results show that the stored procedure method provides consistently from low-intensity to high-intensity environments (links to 200 browser links at the same time). Performance.
More information
If multiple columns and / or rows are returned by the query executed by the ExecuteQuery method, this method only returns to the first column of the first row. See how to use ExecuteScalar to get single data using ExecuteScalar in the appendix using the code snippet using the ExecuteScalar method. About demonstrating how to use the stored procedure output or return parameter acquisition of single data, see how to use the stored procedure output or return parameter acquisition in the appendix to demonstrate how to use the SqlDataReader object to obtain a single data code example, see how to see the appendix Use the SqlDataReader object to get a single data. Establish a link through a firewall
Internet applications are often configured to connect it to SQL Server through the firewall link. For example, many web applications and main structural components of the firewall are peripheral networks (also known as DMZ or non-military zones), which are used to isolate high-end web servers and internal networks.
When connecting to SQL Server through a firewall, you need to configure the firewall, customer, and server. SQL Server provides customer web applications and server web applications to help configure it.
Select the network library
When a link is established via a firewall, use the SQL Server TCP / IP network library to simplify configuration, which is the default option for SQL Server2000 installation. If you use the previous version of SQL Server, you can check if the TCP / IP has been configured as the default network library in the client and server-side network applications.
In addition to configuration advantages, use TCP / IP libraries also means:
Benefiting from the improved performance and increased extensibility of bulk data. Avoid additional security information related to the specified pipeline.
TCP / IP must be configured on the customer and server computer, because most firewall limits the port passing port, so you must carefully consider the port number used by SQL Server.
Server
The default instance of SQL Server is listened to the 1433 port. However, the specified instance of SQL Server 2000 dynamically assigns the port number when they are turned on. Network administrators have hopes to open a range of ports in the firewall; therefore, when using the firewall to specify instances of SQL Server, the instance is configured using the service network application to make it listening to a specific port. The administrator then configures the firewall so that the firewall allows traffic to reach the port listening to a particular IP address and server instance.
Note that the source port number used by the client network library is dynamically allocated between 1024-5000. This is a standard practice for TCP / IP client applications, but this means that the firewall must allow any port traffic to this range to pass. For more information on ports used by SQL Server, see INF: P on the Microsoft Product Support Services website, TCP ports needed to communicate with SQL Server via firewall
. .
Dynamic lookup specified instance
If you change the default port listens to SQL Server, you must configure the client to link it to this port. For more details, see the configuration client in this article
one period.
If the port number of the SQL Server 2000 default instance is changed, the client will cause a link error. If there are multiple SQL Server instances, the latest version of the MDAC data access stack (2.6) will perform dynamic lookup, and the specified instance is positioned using the User Data Bad Protocol (UDP) negotiation (via UDP port 1434). Although this approach may be effective in the development environment, it is not much working in the current environment, because the firewall will prevent UDP negotiation traffic under the typical question.
In order to avoid this, always configure the client to link to the configured destination port number.
Configure the client
The client should be configured to use the TCP / IP network library to SQL Server, and should ensure that the client library uses the correct destination port number.
Use TCP / IP network libraries
With the SQL Server client network library, you can configure the client. In some installation versions, this application may not be installed to the client (such as a web server). In this case, you can solve it as follows:
The specified network library is used with the "NetWork Library = DBMSSOCN" name-value provided by the link string. String DBMSSOCN is used to identify TCP / IP (socket) libraries.
Note that when using the SQL Server .NET data supply, the default settings of the network library use "dbmsoCN".
Modify the registry on the client machine and set TCP / IP to the default library. For more information on configuring the SQL Server network library, see HOWTO: Modify the SQL Server default network library (Q250550) without using the client network application.
Specified port
If the instance of SQL Server is configured to listen to other ports other than the default 1433, then the link to the port number can be specified:
Use the client network application to specify the port number using the "Server" or "Data Source" name-value pair provided to the link string. To use a string according to the format below: "Data Source = ServerName, Portnumber"
Note that ServerName can be an IP address, or a Domain Name System (DNS) name. To optimize performance, you can use an IP address to avoid DNS queries.
Distributed transaction
If you have developed a service component using the COM Distributed Transaction Processing Coordinator (DTC) service, you need to configure the firewall to allow DTC streams to differ between DTC instances and DTC and resource manager (for example SQL Server flows.
For more information on the DTC open port, see INFO: Working through a firewall, configuring a Microsoft Distributed Transaction Coordinator (DTC).
Processing blobs
Currently, many applications have to handle multi-traditional strings and digital data, and data on images or even complex data formats, such as video formats. Data format types of graphics, sound and video are different. However, from a storage perspective, they can be considered as binary data blocks, typically referred to as BLOBS (binary large objects).
SQL Server provides binary, varbinary, and image data formats to store BLOBS. Without the name, the BLOB data can also be referred to as a file-based data. For example, you might want to store binary annotation fields related to a particular row. SQL Server provides NTEXT and TEXT data types for this purpose.
Typically, for binary data less than 8 kB, use Varbinary data types. For binary data exceeding this size, use Image. Table 2 brings together the main features of each data type.
Table 2 Data type characteristics
Data Type Size Description Binary range from 1-8KB. The storage size is a specified size plus 4 bytes. The fixed length binary data Varbinary range ranges from 1-8 kB. The storage size is an actual size of the data plus 4 bytes. Variable Length Binary Data Image From 0-2GB size variable length binary data large-capacity variable length binary data TEXT from 0-2GB size variable length data character type data NTEXT from 0-2GB size variable length data Wide Biode Character Data
Where to store BLOB data
SQL Server 7.0 and its later versions have increased the performance of BLOB data stored in the database. One reason for this is that the database page size has increased to 8KB. As a result, less than 8kb text or image data does not have to store a separate binary tree structure in the page, but can be stored in a single line. This means reading and writing text, ntext, or image data can be as fast as reading or writing characters or binary strings. After 8KB, a pointer will be created in the row, the data itself is stored in the binary structure of the standalone data page, which inevitably generates an impact on performance. For more information to force Text, NText, and Image data to store in a single line, see the use of Text and Image data topics in SQL Server online books.
An optional method for processing BLOB data frequently is that the BLOB data is stored in the file system and stores a pointer in the database column (usually a uniform resource locator -ur link) to reference the correct file. For SQL Server 7.0, you can improve performance in file systems that BLOB data stored outside of the database.
However, SQL Server 2000 improves BLOB support, and ADO.NET supports support for reading and writing BLOB data, making BLOB data in the database into a feasible method.
Advantages of using BLOB data in the database
Store BLOB data in the database, bringing a lot of advantages:
Easy to maintain the synchronization of BLOB data and other items in the row. BLOB data is supported by the database, with a single storage stream, easy to manage. The XML supported by SQL Server 2000 can access BLOB data, which will return 64-bit encoded data in the XML stream. A column that contains a filling or variable length character (including wide character) data can perform SQL Server full text search (FTS) operations. It is also possible to perform FTS operations on the formatted text-Word or Excel document containing formatted text in the Image field.
Write BLOB data into the database
The following code demonstrates how to use ADO.NET to write binary data obtained from a file into the SQL Server Image field.
Public void storePicture (String FileName)
{
// read the file into a byte array
FILESTREAM FS = New FileStream (FileName, Filemode.Open, FileAccess.Read);
Byte [] imagedata = new byte [fs.length];
fs.read (imagedata, 0, (int) fs.length);
fs.close ();
SqlConnection conn = new sqlconnection ("");
Sqlcommand cmd = new SQLCOMMAND ("StorePicture", CONN);
cmd.commandtype = commandtype.storedProcedure;
Cmd.Parameters.Add ("@ filename", filename;
CMD.Parameters ["@ filename"]. Direction = parameterdirection.input;
Cmd.Parameters.Add ("@ blobdata", sqldbtype.image);
CMD.Parameters ["@ blobdata"]. Direction = parameterdirection.input;
// store the byte array within the image fieldcmd.parameters ["@ blobdata"]. Value = imagedata;
Try
{
Cn.open ();
cmd.executenonquery ();
}
Catch
{
Throw;
}
Finally
{
CONN.CLOSE ();
}
}
Read BLOB data from the database
Create a SqlDataReader object by an ExecuteReader method to read a ComMandbehavior.SequentialAlaseravior.SequentialAracse an enumeration value when reading a line containing BLOB data. If this enumerate value is not available, the reader only sends a line of data from the client from the server. If the row contains BOLB data, this indicates that a large amount of memory is to be taken. By utilizing an enumerated value, a better control is obtained because the BLOB data is only issued when it is referenced (for example, using the GetBytes method, you can control the number of bytes). This is shown in the code snippet below.
// Assume Previously Established Command and Connection
// the command selects the Image column from the table
Cn.open ();
SqlDataReader Reader = cmd.executeReader (Commandbehavior.SequentialAraccess);
Reader.Read ();
// Get Size of Image Data - Pass Null As The Byte Array Parameter
Long Bytesize = Reader.getbytes (0, 0, NULL, 0, 0);
// allocate byte array to hold image data
Byte [] imagedata = new byte [bytesize];
Long BytesRead = 0;
INT CURPOS = 0;
While (bytesRead { // chunksize is an Arbitrary Application Defined Value BYTESREAD = Reader.getbytes (0, Curpos, ImageData, Curpos, Chunksize); Curpos = chunksize; } // Byte Array 'ImageData' Now Contains Blob from Database Note Using Commandbehavior.sequentialAndbehavior.sequentialAccess needs to access column data in strict order. For example, if the BLOB data exists in column 3, and it is also necessary to read data from the 1, 2 column, the first, 2 columns must be read before reading the third list. Transaction processing In fact, all commercial applications for updating data sources require transaction support. By providing four basic guarantees, that is, well-known first abbreviations ACID: divided, consistency, separation, and durability, transaction processing will be used to ensure integrity of systems contained in one or more data sources. For example, consider a web-based retail application that is used to handle purchase orders. Each order requires 3 complete different operations, which involves 3 database updates: The inventory level must reduce the number of the order. The amount purchased must be credited to the customer's credit rating. The new order must be added to the database. These three different operations are critical as a unit and automated. Three operations must be all successful, or unsuccessful - any error will disruver data integrity. Transaction processing provides this integrity and other guarantees. To learn more about the basic principles of the transaction process, see http://msdn.microsoft.com/library/en-us/cpguide/html/cpcontransactionProcessingFundamentals.asp. Many methods can be used to merge transaction management into the data access code. Each method is suitable for one of two basic programming models below. Handmade transaction. You can write code that uses ADO.NET or Transact-SQL transaction support feature directly during component code or stored procedures. Automation (COM ) transaction. You can add a declaration to the .NET class to specify the properties required for the object transaction processing at runtime. This model allows you to easily configure multiple components to run them within the same transaction. Although the automated transaction model greatly simplifies the distributed transaction process, both models are used to perform local transaction processing (ie, transaction processing executed for single resource manager such as SQL Server 2000) or distributed transaction (ie, Transaction processing performed on multiple resource management on a remote computer). You may try to benefit from an easy programming model with automation (COM ) transaction. This advantage is more pronounced in a system with multiple components to perform a database update. However, in many cases, additional overhead and performance loss caused by this transactional model should be avoided. This section will guide you to select the most appropriate model based on a specific application environment. Select transaction processing model Before selecting the transaction model, you should first consider whether you really need transaction. Transaction processing is the most expensive resource used by server applications, where they do not use, they reduce scalability. Consider the criteria for managing transaction processing below: Transaction processing is only executed when you need to get a lock and need to enhance the ACID rule. Maintain transaction processing as short as possible to minimize the time to maintain the database lock. Never put our customers in the control of the transaction life cycle. Do not use transaction processing for a single SQL statement. SQL Server automatically performs each statement as a single transaction. Comparison of automated transaction processing and manual transaction processing Although the programming model has been simplified, especially when performing database updates in multiple components, local transaction processing is always quite fast because they do not need to interact with Microsoft DTCs. This is also the case even if you use automated transaction to a single local resource manager (such as SQL Server) (although performance loss is reduced), because the hand-local transaction process avoids all unnecessary communication between the DTC process. For the following cases, manual transactions are required: Perform transaction processing for a single database. For the following conditions, automatic transaction processing should be used: You need to extend a single transaction to multiple remote databases. A single transaction is required to have multiple resource managers (such as databases and Windows 2000 message queues (called MSMQ) resource managers). Pay attention to avoid mixing transaction processing models. It is best to use only one. In an application environment in which performance is good, (even for a single database) Select Automated Transaction to simplify the programming model, this practice is reasonable. Automated transaction processing allows multiple components to easily perform multiple operations in the current transaction process. Handmade transaction For manual transaction processing, you can write code using the ADO.NET or Transact-SQL transaction support feature in the component code or stored procedure. In most cases, you should choose to control transaction during storage, as this method provides higher encapsulation, and in terms of performance, this method is compatible with transaction with ADO.NET code. Use ADO.NET to perform manual transaction processing ADO.NET supports transaction objects, using this object to start a new transaction process, and explicitly control whether transaction processing is executed or rollback. Transaction objects are related to a single database link, which can be obtained by a BEGINTRANSACTION method of the link object. Calling this method is not implying that the next command is issued in the transaction context. Each command must be associated with transaction by setting the transaction property of the command. Multiple command objects can be associated with transaction objects, so multiple operations are packet in a single transaction in a single transaction. For examples of using the ADO.NET transaction code, see how to encode ADO.NET manual transaction in the appendix. More information ADO.NET manual transaction processing default separation level is read, which means that the database controls shared lock when reading data, but data can be modified before the end of transaction processing. This situation potentially produces non-repeatable reading or virtual data. The separation level can be changed by setting the ISOLALATIONLEVEL attribute of the transaction object to the ISOLATIONLEVEL enumeration type. The appropriate separation level must be selected carefully for transaction. It is compromised to the proportion of data consistency and performance. The highest separation level (serialized) provides absolute data consistency, but at the expense of the overall throughput of the system. The lower separation level will make the application easier to expand, but at the same time increase the possibility of errors due to inconsistencies of data. The lower separation grade is suitable for systems that read data in most time, with a minimum write data. Regarding the election of the appropriate transaction level, it is very valuable, see Microsoft Publishing House, known as INSIDE SQL Server 2000, Author Kalen delaney. Use the stored procedure to perform manual transaction processing You can also directly control the manual transaction processing using the Transact-SQL statement during the stored procedure. For example, transaction processing can be performed using a stored procedure containing Transact-SQL transaction statements such as Begin Transaction, End Transaction, and Rollback Transaction. More information If necessary, use the SET TRANSACTION ISOLATION LEVEL statement to control the separation level of the transaction processing during the stored procedure. Reading is the default setting for SQL Server. For more information on SQL Server Separation Level, see Separation Levels in SQL Server Online Book "Access and Modify Data" section. About demonstrating how to use Transact-SQL transaction statements to execute transaction updates, see How to use Transact-SQL to perform transaction processing in the appendix. Use automation transactions Automated transactions simplify programming models because they do not need to explicitly begin a new transaction process, or clearly execute or cancel transactions. However, the biggest advantage of automated transactions is that they can be combined with DTC, which makes a single transaction to be extended to multiple distributed data sources. This advantage is important in large distributed applications. Although it is possible to control distributed transactions by manual DTC, it is possible to control distributed transactions, but automated transaction has greatly simplified workload, and it is designed for components-based systems. For example, a plurality of components can be conveniently configured to perform tasks that contain a single transaction process. Automated transactions depends on distributed transaction processing support features provided by COM . As a result, only the service component (ie, the components derived from the ServicesDComponent class) can use automated transactions. To process the configuration class for an automated transaction, the operation is as follows: Delicate new categories from the ServicComponent class located in the EnterpriseServices namespace. Define the transaction requirements of the class through the Transaction property. Enumeration values from TransactionOption determine how to configure classes in the COM class. Other attributes that can be set together with this property include transactional separation levels and timeout caps. In order to avoid that the transaction results must be explicitly selected, the method can be annotated with the AutoComplete property. If these methods are released, the transaction will be canceled. Note that if needed, you can directly select the transaction results. For more details, see section for the result of the transaction processing later. More information For more information on COM automation transactions, search for "Automation Transaction through COM " can be searched in platform SDK documents. For examples of the .ne T transaction processing class, see How to encode .NET transaction in the appendix. Configure transaction processing separation level The transaction separation level used for COM 1.0 - i.e., the COM --AM --water running is serialized. This provides the highest separation level, which is based on performance. The overall throughput of the system is reduced. Because the resource manager (typically the database is typically) must keep reading and writing during transaction processing. During this time, all other transactions have been blocked, which will greatly impact the application's extension capabilities. With the COM version 1.5 version issued with Microsoft Windows .NET Allows the Component Configuration Transaction Separation Level in the COM directory. Settings related to the root component of the transaction determines the separation level of transaction processing. In addition, the transaction level owned by the internal subcomponents in the same transaction stream must not be higher than the level defined by the component. If this is not the case, when the child component is instantiated, it will cause an error. For the .net management class, the Transaction property supports all public isolation properties. You can use this attribute to specify a special separation level, as shown in the following code: [Transaction (TransactionOption.supported, Isolation = TransactioniSolationledLevel.Readcommitted)] Public Class Account: ServicedComponent { . } More information For more information on configuring transactional separation levels and other Windows .NET COM enhancements, see MSDN Magazine 2001 "Windows XP: Use Com 1.5 Enhancement Characteristics to make your components stronger". Determine transaction results In all transaction processing components of a single transaction stream, automated transaction results are determined by the status of transaction cancellation flags and consistency logos. When the root assembly in the transaction stream becomes a non-active state (and control returns the caller), the transaction results are determined. This situation has been demonstrated in Figure 5, which shows a typical bank fund transferred transaction. Figure 5 Transaction flow context When the root object (in this example is an object), it is determined when the customer's method call returns, and the transaction result is determined. Any consistency logo in any context is set to false, or if the transaction cancel flag is set to true, then the underlying physical DTC transaction will be canceled. You can control the transaction results from the .NET object from the .NET object in one of the following methods: You can use the AutoComplete property to comment on the method and let the .NET automatically stores to decide the transaction results vote. If the method releases exception, this property is utilized, the consistency flag is automatically set (this value finally cancels the transaction). If the method returns without release an abnormality, then the consistency flag will be true. This value indicates that the component is happy to perform transactions. This is not guaranteed because it relies on voting of other objects in the same transaction. You can call the static method setComplete or setabort of the ContextUtIL class, which makes the consistency flags true or false separately. SQL Server errors in severeity greater than 10 will cause the management data supplier to release the exception of the SQLEXCeption type. If the method caches and processes an exception, be sure to cancel the transaction manually, or the method is marked with [AutoComplete] to ensure that the exception can pass the caller. AutoComplete method For a method marked attribute, do the following: Pass the SQLException to call the stack. Pack the SQLEXCEPTION in an external exception and pass back the caller. It is also possible to encapsulate an exception type that is more meaningful to the call. If you can't pass, it will cause the object to not put forward the transaction, so that the database error is ignored. This means that the successful operation of the other objects of sharing the same transaction will be submitted. The following code caches SQLException and then passes it directly back to the caller. Transaction processing will eventually be canceled because the consistency flag of the object is automatically set to false when the object changes inactive. [AutoComplete] Void someMethod () { Try { // Open the connection, and perform Database Operation . } Catch (SQLEXCEPTION SQLEX) { LOGEXCEPTION (SQLEX); // Log the Exception Details Throw; // Rethrow the Exception, Causeing the consistent // flag to be set to false. } Finally { // Close The Database Connection . } } Non-autocomlete method For methods for the properties without AutoComplete, must: Call ContextUtil.Setabort in the CatCH block to terminate transaction. This sets the compatible flag to false. If no exception event occurs, call ContextUtil.setComplete to submit a transaction, which sets the compatible flag to true (default). The code illustrates this method. Void someharmthod () { Try { // Open the connection, and perform Database Operation . Contextutil.setComplete (); //manually vote to commit the transport } Catch (SQLEXCEPTION SQLEX) { LOGEXCEPTION (SQLEX); // Log the Exception Details Contextutil.Setabort (); // manally vote to abort the transaction // Exception is Handled At this point and is not propagated to the caller } Finally { // Close The Database Connection . } Note If there are multiple Catch blocks, call ContextVtil.Setabort when the method starts, and call ContextUtIl.setComplete at the end of the TRY block will become easy. With this method, you don't need to repeat the conteutil.setabort in each CatCH block. The setting of the compatible marker determined by this method is only valid when the method is returned. For exception events (or loop exception), it must be passed to the calling stack because it makes the calling code that transaction failed. It allows calling code to make optimized selections. For example, in bank fund transfers, if the debt operation fails, the transfer branch can determine that the debt operation is not executed. If the compatible flag is set to a false and there is no exception event when returning, there is no way to call the code if the transaction will certainly fail. Although the Boolean value can be returned or the Boolean output parameter is set, it should still be consistent, and the abnormal event should be displayed to indicate that there is an error. This code has a standard error handling method, so it is more concise, more compatibility. Data page Paging in distributed applications is a universal requirement. For example, the user may get a list of books and the list is not fully displayed. Users need to perform some familiar operations on the data, such as browsing the next page or the previous page, or jumps to the first page of the list. Or the last page. This part of the content will discuss options for implementing this feature, as well as each option in performance and scaling. Option comparison The options for data paging are: With SQLDataAdapter's Fill method, the results from the query are filled into the DataSet. Use ADO to use ADO through COM, and utilize server cursors. Manually implement data paging by using the stored process. The optimal option for paging data depends on the following factors: Scalability Requirements Requirements Requirements Network Bandwidth Database Server Memory and Power Intermediate Server Memory and Power By Size of Row Data Numbers Returned by Paging Queries Performance tests show that the manual method of the stored procedure provides optimal performance in a large stress level. However, because the manual method is executed on the server, if most of the site features rely on the data paging function, the server performance will become a key element. To ensure that this method is suitable for special environments, you should test all kinds of special requirements. A variety of different options will be discussed below. Use SqlDataAdapter As discussed earlier, SqlDataAdapter is used to populate data from the database into the DataSet, and any of the overloaded Fill methods require two integer index values (as shown in the following code): Public Int Fill DataSet DataSet, Int StartRecord, Int MaxRecords, String Srctable ); The StartRecord value indicates the starting index value from zero. The maxRecord value represents the number of records starting from StartRecord and copies them into the new DataSet. SqlDataAdapter uses SqlDataReader to perform queries and returns the result. SqlDataAdapter reads the results and creates a DataSet based on data from SalDataReader. SqlDataAdapter copies all results through StartRecord and MaxRecords to the new generation of DataSet and discard unwanted data. This means that many unnecessary data will have potentially access to data through the network - this is the main defect of this method. For example, if there is 1000 records, it is required to be 900 to 950 records, then 899 records in front will still cross the network and then dropped. For small number of records, this overhead may be relatively small, but if you target a large amount of data, this overhead will be very huge. Use ADO Another option to implement paging is to use COM-based ADO to page. The goal of this approach is to access the server cursor. The server cursor is displayed via the ADO Recordset object. You can set the location of the Recordset cursor to the AduseServer. If your OLE DB supplier supports this setting (such as SQLOLEDB), you can use the server cursor. This allows the cursor to navigate directly to the starting record without the need to pass all data to the user code of access data. This method has the following two shortcomings: In most cases, it may be necessary to translate records returned to the Recordset object into content in the DataSet to use in the customer-managed code. Although OLEDTAADAPTER is indeed acquiring the ADO Recordset object and translating it into DataSet, there is no function of starting and ending using special records. The only reality option is to move the start record to the Recordset object, loop each record, and then copy data to the new DataSet that manually generated. This kind of operation, especially using COM Interop, which advantage may not only do not need to transmit excess data on the network, especially for small Dataset more obvious. The connection and server cursor are open when the required data is output from the server. On the database server, open and maintenance of cursors require expensive resources. Although this option increases performance, it is possible to reduce scalability due to extended time two-consuming server resources. Provide manual implementation The last option of the data paging discussed in this section is to use the stored procedure to manually implement the page features of the application. For tables that contain unique keywords, the stored procedure is relatively easy. And for tables without a unique key (there should not be many keywords), which is relatively complex. Paging with a single keyword If the table contains a unique keyword, you can use the keywords in the WHERE Terms to create the result settings from a special row. This method is to match the SET ROWCOUNT state used to limit the size setting size, which provides a valid patch principle. This method will be described in the code stored below: Create Procedure GetProductSpaged @LastProductId Int, @PageSize Int AS Set rowcount @PageSize SELECT * From product Where [Standard Search Criteria] And Productid> @LastProductID Order by [criteria That Leaves Productid Monotonically Increasing] Go The calling program of this stored procedure only maintains the value of the LastProductID and increases or decreases the value by the size between the selected continuous calls. Paging in forms with unique keywords If you need a paging table without a unique keyword, you can consider adding one - such as using the identity column. This allows the paging scheme discussed above. As long as you can create uniqueness by combining two or more areas in the results record, it is still possible to implement a valid paging scheme without a unique keyword table. For example, investigate the following form: Col1col2col3other column ... a1w ... a1x .a1y .a1z .a2w .a2x .b1w ... b1x. For this table, combined with COL, COL2, and COL3 may have a uniqueness. In this way, the distribution principle can be implemented using methods in the following stored procedures: Create Procedure RetrievedataPaged @LastKey Char (40), @PageSize Int AS Set rowcount @PagesizesEct COL1, Col2, Col3, Col4, Col1 Col2 Col3 As Keyfield From SampleTable Where [Standard Search Criteria] And Col1 Col2 Col3> @LastKey Order By Col1 ASC, Col2 ASC, Col3 ASC Go The customer keeps the final value of the Keyfield column returned by the stored procedure, and then inserts back to the stored procedure to control the paging of the table. Although manual implementation increases the strain on the database server, it avoids unnecessary data on the network. Performance tests indicate that this method is working well throughout the strain level. However, based on the data paging function involved in the site, manually paging on the server may affect the scalability of the application. Performance tests should be run in the environment, find the most appropriate way for the application. appendix How to enable object structure for a .NET class To use Enterprise (COM ) Services to enable .NET management classes to the object structure, you need to perform the following steps: Guide the required class from the Servic Component located in the SYSTEM. Enterprise Services namespace. Using system.enterprises; Public Class DataAccessComponent: ServicesDComponent Adds a construction enabled attribute for this class and specifies the default structure string. The default value is saved in the COM directory, and the administrator can use the component service Microsoft Management Console (MNC) Snap-in. To maintain the default. [Constructionenabled (default = "default dsn")] Public Class DataAccessComponent: ServicesDComponent provides a replacement implementation of a virtual construct method. This method is called after the object language constructor. The structure string saved in the COM directory is the unique string of the method. Public override void construct (String ConstructionString) { // Construct Method Is Called Next After Constructionor. // the configured dsn is supplished as the single argument } Provide a strong name for the assembly via the Assembly key file or the Assembly key name property. Any compilation that uses COM service registration must have a strong name. About more information on stronger name assembly, reference: http://msdn.microsoft.com/library/en-us/cpguide/html/cpconworkingwithstrongly- namedassemblies.asp. [Assembly: AssemblyKeyFile ("DataServices.snk")] To support dynamic registration, you can specify the name of the COM application for maintaining assembly elements and application action types, respectively, using attributes ApplicationName and Application Action, respectively. More information about assembly registration, reference: http://msdn.microsoft.com/library/en-us/cpguide/html/cpconregisteringserviced components.asp. // the applicationname attribute specifies the name of the name // COM Application Which Will Hold Assembly Components [Assembly: ApplicationName ("Dataservices")]] // the applicationActivation.ActivationOption Attribute Specifies // WHERE Assembly Components Are Loaded ON Activation // Library: Components Run in The Creator's Process // Server: Components Run in a System Process, Dllhost.exe [assmbly: ApplicationActivation (ActivationOption.Library)] The following code segment is a service component called DataAccessComponent that uses the COM structure string to get a database connection string. Using system; Using system.enterprises; // the applicationname attribute specifies the name of the name // COM Application Which Will Hold Assembly Components [Assembly: ApplicationName ("Dataservices")]]] // the applicationActivation.ActivationOption Attribute Specifies // WHERE Assembly Components Are Loaded ON Activation // Library: Components Run in The Creator's Process // Server: Components Run in a System Process, Dllhost.exe [assmbly: ApplicationActivation (ActivationOption.Library)] // sign the assembly. The snk key file is created Using the THE // sn.exe utility [Assembly: askEMBLYKEYFILE ("Dataservices.snk")]] [Constructionenabled (default = "default dsn")] Public Class DataAccessComponent: ServicesDComponent { PRIVATE STRING CONNECTIONSTRING; Public DataAccessComponent () { // Constructor is Called On Instance Creation } Public override void construct (String ConstructionString) { // Construct Method Is Called Next After Constructionor. // the configured dsn is supplished as the single argument THIS.CONNECTIONSTRING = ConstructString; } } How to use SqlDataAdapter to retrieve multiple lines The following code shows how to use the SqlDataAdapter object to issue a command to generate a Data SET or DATATABLE. It retrieves a series of catalogs from the SQL Server Northwind database. Using system.data; Using system.data.sqlclient; public dataatable RetrieverowswithDataTable () { Using (SqlConnection Conn = New SqlConnection (Connectionstring)) { SQLCommand cmd = new SQLCommand ("DatretrieveProducts", Conn; cmd.commandtype = commandtype.storedProcedure; SqlDataAdapter Da = New SqlDataAdapter (CMD); DataTable DT = New DataBLE ("Products"); Da.fill (DT); Return DT; } } Press the following steps to use SQLADAPTER to generate DataSet or DataTable: Create a SQLCommand object Enable the stored procedure and connect it with the SQLConnection object (display) or connection string (not shown). Create a new SqlDataAdapter object and link it to your SQLCommand object. Create a DataTable (or DataSet) object. Use the constructor to name DataTable from the variable. Call the Fill method of the SQLData Adapter object, transfer the retrieval line to DataSet or DataTable. How to use SqldataReader to retrieve multiple lines The following code illustrates how to retrieve multi-line using the SqlDataReader method: Using system.io; Using system.data; Using system.data.sqlclient; Public SqlDataReader RetrieverowswithDataReader () { SqlConnection conn = new SQLCONNECTION "Server = (local); Integrated Security = SSPI; Database = Northwind"); SQLCommand cmd = new SQLCommand ("DatretrieveProducts", Conn; cmd.commandtype = commandtype.storedProcedure; Try { Cn.open (); // generate the reader. ComMMandbehavior.closeConnection Causes the // the connection to be closed when the reader object is closed Return (cmd.executeReader (CMMANDBEHAVIOR.CLOSECONNECONNECONNECONNECONNECONNECONNECONNECTION); } Catch { CONN.CLOSE (); Throw; } } // Display the Product List sale the console Private void displayproducts () { SqldataReader Reader = RetrieverowswithDataReader (); While (Reader.Read ()) { Console.writeline ("{0} {1} {2}", Reader.GetInt32 (0) .tostring (), Reader.getstring (1)); } Reader.close (); // Also Closes The Connection Due To The Connection Due To THE // Commandbehavior Enum Used Whenrating The Reader } Press the following steps to use SqlDataReader to search multi-line: Create a SQLCommand object for executing the stored procedure and link it to the SQLConnection object. Open the link. Generate a SQLDataReader object by calling the Excute Reader method of the SQLCommand object. Read data from the stream, call the READ method of the SQLDataReader object to retrieve the row, and use the classified access program method (such as the Getiut 32 and Get String method) to search the column. When reading, call the Close method. How to use XmlReader to search multiple lines You can generate an XMLReader object using a SQLCommand object that provides a stream-based forward access to XML data. This command (usually a stored process) must generate an XML-based result setting, which is usually composed of SQL Server2000 consisting of a SELECT state with valid Terms for XML. The following code segment illustrates this method: Public void retrieveandDisplayRowsWithxmlReader () { SqlConnection Conn = New SqlConnection (Connectionstring); Sqlcommand cmd = new sqlcommand ("DATRETRIEVEPRODUCTSXML", CONN); cmd.commandtype = commandtype.storedProcedure; Try { Cn.open (); XmlTextReader XReader = (XMLTextReader) cmd.executexmlreader (); While (XReader.Read ()) { IF (XReader.name == "Products") { String stroutput = xreader.getattribute ("productID"); Stroutput = "" Stroutput = xreader.getattribute ("productname"); Console.writeLine (stroutput); } } XReader.close (); } Catch { Throw; } Finally { CONN.CLOSE (); } } The above code uses the following stored procedures: Create Procedure DatretrieveProductsXML AS Select * from products For xml auto Go Retrieve XML data by following these steps: Creating a SQLCommand object Enables the generation of the XML result settings. (For example, using the For XML terms in the SELECT state). Contact the SQLCOMMAND object with a link. Call the EXECUTEXMLREADER method for the SQLCommand object and assign the result to the forward object XMLTextReader. This is the fastest type of XMLReader object that should be used if any of the XML-based authentication that returns data is not required. Read the data using the read method of the XMLTextReader object. How to use stored procedure output parameters to retrieve single line A stored procedure can be called, which can return to retrieval data items in a single row in a single row by means of an output parameter. The following code segments use the stored procedure to retrieve the name and unit price of the product, which is included in the Northwind database. Void getProductDetails (int Productid, Out String ProductName, Out Decimal Unitprice) { SqlConnection conn = new SQLCONNECTION "Server = (local); Integrated Security = SSPI; Database = Northwind"); // set up the command Object used to execute the stored proc Sqlcommand cmd = new sqlcommand ("DatgetProductDetailspoutput", CONN); cmd.commandtype = commandtype.storedProcedure; // establish stored proc parameters. @ProductID Int Input @ProductName Nvarchar (40) Output @Unitprice Money Output // Must Explicitly Set The Direction of Output Parameters Sqlparameter paramprodid = Cmd.Parameters.Add ("@ProductID", ProductID; Paramprodid.direction = parameterdirection.input; Sqlparameter paramprodname = CMD.Parameters.Add ("@ProductName", SqldbType.varchar, 40); ParamProdname.direction = parameterDirection.output; Sqlparameter paramunitprice = Cmd.Parameters.Add ("@unitprice", sqldbtype.money); Paramunitprice.direction = parameterdirection.output; Try { Cn.open (); // Use ExecutenonQuery to run the commit. // Alth No Rows Are Returned Any Mapped Output Parameters // (and potentially returnes) Are Populate cmd.executenonquery (); // Return Output Parameters from stored Proc ProductName = paramprodname.value.toString (); Unitprice = (decimal) paramunitprice.value; } Catch { Throw; } Finally { CONN.CLOSE (); } } Use the stored procedure output parameter to retrieve a single line: Create a SQLCOMMAND object and link it to the SQLConnection object. Set the stored procedure parameters by calling the Add method of the SQLCommand's Parameters collection. By default, the parameters are assumed to be output, so the direction of any output parameters must be explicitly set. Note that the direction of all parameters is clear is a good exercise, including input parameters. Open the connection. Call the EXECUTENONQUERY method for the SQLCommand object. It is in output parameters (and potentially with a return value). Use the Value property to retrieve the output parameters from the appropriate SQLParameter object. Close the connection. The above code segment enables the following stored procedures. Create Procedure DatgetProductDetailsspoutput @ProductID INT, @ProductName Nvarchar (40) Output, @Unitprice Money Output AS SELECT @ProductName = ProductName, @Unitprice = Unitprice From product Where productid = @ProductID Go How to use SqlDataReader to retrieve a single line You can search the single row using the SqlDataReader object, and the value from the required column that returns the data stream. This is described by the following code: Void getProductDetailsusingReader (int products) Out String ProductName, Out Decimal Unitprice { SqlConnection conn = new SQLCONNECTION "Server = (local); Integrated Security = SSPI; Database = Northwind"); // set up the command Object used to execute the stored proc Sqlcommand cmd = new sqlcommand ("DatgetProductDetailsReader", CONN); cmd.commandtype = commandtype.storedProcedure; // establish stored proc parameters. @ProductID Int Input Sqlparameter paramprodid = cmd.parameters.add ("@ProductID", ProductID; Paramprodid.direction = parameterdirection.input; Try { Cn.open (); SqlDataReader Reader = cmd.executeReader (); Reader.read (); // advance to the one and only row // Return Output Parameters from Returned Data Stream ProductName = Reader.getstring (0); Unitprice = reader.getDecimal (1); Reader.Close (); } Catch { Throw; } Finally { CONN.CLOSE (); } } Follow these steps to return to with the SqlDataReader object: Establish a SQLCommand object. Open the connection. Call the ExecuteReader object of the SQLDReader object. Retrieve the output parameters using the classification of the SqlDataReader object - here is getString and getDecimal. The following code segments are enabled by the following stored procedures: CREATE Procedure DatgetProductDetailsReader @ProductID Int AS Select ProductName, Unitprice from Productswhere ProductId = @ProductID Go How to use ExecuteScalar single item The ExecuteScalar method is to design access to a single value. In returns multiple columns or multi-line access events, ExecuteScalar only returns the first example of the first line. The following code shows how to query the product name of a product ID: Void getProductNameexecutescalar (int Productid, Out String ProductName) { SqlConnection conn = new SQLCONNECTION "Server = (local); Integrated Security = SSPI; Database = Northwind"); Sqlcommand cmd = new SQLCOMMAND ("LookuppproductNamescalar", Conn; cmd.commandtype = commandtype.storedProcedure; Cmd.Parameters.Add ("@ ProductID", ProductId; Try { Cn.open (); ProductName = (string) cmd.executescalar (); } Catch { Throw; } Finally { CONN.CLOSE (); } } Use the following steps to use Execute Scalar to retrieve a single item: Establish a SQLCommand object that calls the stored procedure. Open the link. Call the ExecuteScalar method, pay attention to the method to return to the object type. It contains values of the first column of retrieved and must be designed to be appropriate. Close the link. The above code enables the following stored procedures: Create Procedure LookuppproductNamescalar @ProductID Int AS SELECT TOP 1 ProductName From product Where productid = @ProductID Go How to use the stored procedure output or returned parameters to retrieve a single item Using the parameters output or returned by the stored procedure can query a single value, the following code illustrates the use of output parameters: Void getProductNameusingsingsPoutPut (int ProductId, Out String ProductName) { SqlConnection conn = new SQLCONNECTION "Server = (local); Integrated Security = SSPI; Database = Northwind"); Sqlcommand cmd = new SQLCommand ("LookuppproductNamesPoutput", CONN); cmd.commandtype = commandtype.storedProcedure; SQLParameter paramprodid = cmd.parameters.add ("@ productID", productID; Paramprodid.direction = parameterdirection.input; Sqlparameter parampn = CMD.Parameters.Add ("@ ProductName", SqldbType.varchar, 40); PARAMPN.DIRECTION = parameterDirection.output; try { Cn.open (); cmd.executenonquery (); ProductName = parampn.value.tostring (); } Catch { Throw; } Finally { CONN.CLOSE (); } } Use the following steps to use the output parameter of the stored procedure to retrieve the single value: Create a SQLCommand object that calls the stored procedure. Set any input parameters and a single output parameter by adding SQLPARMeters to the SQLCommand's parameters collection. Open the link. Call the EXECUTE NONQUERY method for the SQLCommand object. Close the link. Retrieve the output value with the Value property of the output SQLParameter. The above code uses the following stored procedures: Create Procedure LookuppRoductNamespoutput @ProductID INT, @ProductName Nvarchar (40) Output AS SELECT @ProductName = ProductName From product Where productid = @ProductID Go The following code shows how to use the return value to determine if there is a special line. From an encoding point of view, this is similar to the use of stored procedure output parameters, in addition to the SQLParameter direction that needs to be explicitly set to ParameterDirection.ReturnValue. Bool CheckProduct (int products) { SqlConnection conn = new SQLCONNECTION "Server = (local); Integrated Security = SSPI; Database = Northwind"); Sqlcommand cmd = new sqlcommand ("CheckProductSP", CONN); cmd.commandtype = commandtype.storedProcedure; Cmd.Parameters.Add ("@ ProductID", ProductId; Sqlparameter paramret = Cmd.Parameters.Add ("@ productuctexists", sqldbtype.int; Paramret.direction = parameterDirection.ReturnValue; Try { Cn.open (); cmd.executenonquery (); } Catch { Throw; } Finally { CONN.CLOSE (); } Return (int) paramret.value == 1; } According to the following steps, you can use the stored procedure return value to check if there is special line: Establish a SQLCommand object that calls the stored procedure. Set the input parameters of the main keywords that contain the rows that need to be accessed. Set a single return value parameter. Add the SQLParameter object to the SQLCommand's Parameter collection and set it to ParameterDireetion.ReturnValue. Open the link. Call the method of ExecuteNonQuery of the SQLCommand object. Close the link. Retrieve the return value by using the Value property of the return value SQLParameter. The above code uses the following stored procedures: Create Procedure CheckProductSP @ProductID Int AS IF EXISTS (Select ProductidFrom Products Where produter = @ProductID) Return 1 Else Return 0 Go How to use SqlDataReader to retrieve a single item. By calling the ExecuteReader method of the command object, you can use the SqlDataReader object to obtain a single output value. This requires a little more code, because the SqlDataReader Read method must be called, then the required value is retrieved by the reader access program method. The use of the SqlDataReader object is described in the following code: Bool CheckProductWithreader (int products) { SqlConnection conn = new SQLCONNECTION "Server = (local); Integrated Security = SSPI; Database = Northwind"); Sqlcommand cmd = new sqlcommand ("CheckProductexistSwithcount", conn); cmd.commandtype = commandtype.storedProcedure; Cmd.Parameters.Add ("@ ProductID", ProductId; CMD.Parameters ["@ productID"]. Direction = parameterdirection.input; Try { Cn.open (); SqldataReader Reader = cmd.executeReader Commandbehavior.sing Leresult); Reader.Read (); Bool BRecordexists = Reader.Getint32 (0)> 0; Reader.Close (); Return BRecordexists; } Catch { Throw; } Finally { CONN.CLOSE (); } } The above code uses the following stored procedures: Create Procedure CheckProductexistSwithcount @ProductID Int AS Select Count (*) from Products Where productid = @ProductID Go How to encode ADO.NET manual affairs The following codes explain how to use the SQL Server. NET data supplies to protect the bold transfer operation of the transaction. This operation is transferred between two accounts located in the same database. Public void Transfermoney (String toaccount, String fromaccount, Decimal Amount) { Using (SqlConnection Conn = New SqlConnection) "Server = (local); Integrated Security = SSPI; Database = SimpleBank")) { Sqlcommand cmdcredit = new SQLCOMMAND ("Credit", CONN); cmdcredit.commandtype = commandtype.storedProcedure; Cmdcredit.Parameters.Add (New SqlParameter ("@ Accountno", toaccount); Cmdcredit.Parameters.Add ("@ amount", amount); sqlcommand cmddebit = new sqlcommand ("debit", conn); CMDDebit.commandtype = commandtype.storedProcedure; Cmddebit.Parameters.add (New Sqlparameter ("@ Accountno", fromaccount); Cmddebit.Parameters.Add (New Sqlparameter); Cn.open (); // start a new transaction Using (SqlTransaction Trans = Conn.BegintransAction ()) { // Associate the two of the sand of the Same Transaction Cmdcredit.transaction = trans; Cmddebit.Transaction = Trans; Try { cmdcredit.executenonquery (); Cmddebit.executenonquery (); // Both Commands (Credit and Debit) WERE SUCCESSFUL TRANS.COMMIT (); } Catch (Exception EX) { // Transaction Failed TRANS. ROLLBACK (); // log exception details. Throw EX; } } } } How to use Transact-SQL to perform transactions The following stored procedures describe how to perform a bin transfer operation of transactions within the Transact-SQL process. Create Procedure MoneyTransfer @Fromaccount Char (20), @Toaccount Char (20), @Amount Money AS Begin Transaction - Perform Debit Operation Update Accounts Set balance = balance - @amount Where accountnumber = @Fromaccount IF @@ rowcount = 0 Begin Raiserror ('Invalid from Account Number', 11, 1) Goto Abort End Declare @Balance Money SELECT @Balance = Balance from Accounts Where accountnumber = @Fromaccount IF @balance <0 Begin Raiserror ('Insufficient Funds', 11, 1) Goto Abort End - Perform Credit Operation Update Accounts Set balance = balance @amount Where accountnumber = @toaccount IF @@ rowcount = 0 Begin Raiserror ('Invalid To Account Number', 11, 1) Goto Abortend Commit transaction Return 0 Abort: Rollback Transaction Go This stored procedure uses Begin Transaction, Commit Transaction, and Rollback Transaction status manual controlled transactions. How to encode a transactional .NET class The following examples are three service NET classes, they are configured or used for automatic transactions. Each class comes with a Transaction property, which will determine if a new transaction stream or a data stream is shared if the object is shared. These elements work together to perform bank billet transfer. The Transfer class is configured with the RequiresNew transaction property, while the debits and CREDIT classes are configured with the request attribute. This way, share the same transaction three objects when running. Using system; Using system.enterprises; Transaction (TransactionOption.Requiresnew)] Public Class Transfer: ServicedComponent { [AutoComplete] Public void Transfer (String toaccount, String fromaccount, Decimal AMOUNT) { Try { // perform the debit operation DEBIT Debit = New Debit (); Debit.debitaccount (fromaccount, amount); // Perform the Credit Operation Credit Credit = New Credit (); Credit.creditaccount (Toaccount, Amount); } Catch (SQLEXCEPTION SQLEX) { // Handle and Log Exception Details // Wrap and Propagate the Exception Throw New TransferaXception ("Transfer Failure", SQLEX); } } } [Transaction (TransactionOption.Required)] Public Class Credit: ServicedComponent { [AutoComplete] Public void Creditaccount (String Account, Decimal Amount) { SqlConnection conn = new SQLCONNECTION "Server = (local); integrated security = SSPI"; Database = "SimpleBank"); Sqlcommand cmd = new sqlcommand ("CREDIT", CONN); cmd.commandtype = commandtype.storedProcedure; Cmd.Parameters.Add (New Sqlparameter ("@ Accountno", Account); cmd.Parameters.Add (New Sqlparameter); Try { Cn.open (); cmd.executenonquery (); } Catch (SQLEXCEPTION SQLEX) { // log exception details here Throw; // propagate exception} } } [Transaction (TransactionOption.Required)] Public Class Debit: ServicedComponent { Public void debitaccount (String Account, Decimal Amount) { SqlConnection conn = new SQLCONNECTION "Server = (local); integrated security = SSPI"; Database = "SimpleBank"); SQLCommand cmd = new sqlcommand ("debit", conn); cmd.commandtype = commandtype.storedProcedure; Cmd.Parameters.Add (New Sqlparameter ("@ Accountno", Account); cmd.Parameters.Add (New Sqlparameter); Try { Cn.open (); cmd.executenonquery (); } Catch (SQLEXCEPTION SQLEX) { // log exception details here Throw; // Propagate Exception Back to Caller } } } Partner Thank you very much for the following writers and reviewers: Bill Vaughn, Mike Pizzo, Doug Rothaus, Kevin White, Blaine Dokter, David Schleifer, Graeme Malcolm, Bernard Chen, Matt Drucke and Steve Kirk. What kinds of questions, comments and suggestions are readers? Regarding feedback from this article, please send e-mail to devfdbck®Microsoft.com. Do you want to learn and use the powerful features of .NET? Work together with the technical experts of the Microsoft Technology Center to learn to develop the best solutions. For more information, please visit: http://www.micrsoft.com/business/services/mtc.asp.
