Three-layer structure and its application
Concept and environment
The three-layer results development method in ASP.NET, in fact, their thoughts are the same as Java. The three-layer architecture in Java is the front-end HTML, JSP, Servlet, the intermediate layer is JavaBean, EJB, and later is a database server. In ASP.NET, the front section is HTML, ASP, ASPX, etc., the intermediate layer is a .dll control, which is compiled. DLL control, and later is a database server.
In our three-layer architecture, our database layer is connected to the intermediate layer, and the front end passes the parameters to the intermediate layer, and accepts the parameters of the intermediate layer. In our ASP.NET, we focus on our intermediate layer and front-end data interaction.
We generally collect the intermediate layer as a component, and the components can be compiled with .vb, can also be compiled with .cs files. The intermediate layer is generally a .dll file. Microsoft's .NET technology is coming from this aspect than his previous version, which is also one of its hits. We have to register a .dll file, there is a registration is a restart, and on .NET, our .dll file is used, no need to consider registration questions.
Before there is no Visual Stutio.net, we use the .bat file to compile the .vb and .cs files into a .dll file, in the .bat file, we write the compiled file name, the associated name space, Compiled file name and the corresponding command name, then run. It sounds very complicated, which is also what many beginners are fear when compiling the first .dll file. But it is easy to do. Let's take an example to illustrate the writing of the .bat file, assume that we have a file name: saidy.vb file, we have to compile it into Saidy.dll files, which use system, system.data, system. Data.sql namespace, we can create a dblink.bat file, the content is as follows:
VBC /OUT:../bin/saidy.dll / t: library /r :system.dll /r:system.data.dll / r: system.data.sql.dll
DBLINK.VB
This is a command to compile the .vb program, if it is compiled .cs file, the command will be different. We assume that there is a Saidy.cs file, according to the above requirements, we compile:
CS /out:../bin/saidy.dll / t: library /r:system.dll /r:system.data.dll / r: system.data.sql.dll
DBLINK.CS
We can see that most of them are the same.
Of course, if we have a Microsoft's VS.NET programming environment, we don't have to comply with such a compilation .dll file like compiling VB or VC programs. Microsoft's VS.NET is a set of companies that integrate various languages, and can write out different languages in this environment. Specific applications We will introduce them in specialized chapters.
An example of a three-layer architecture
Through the specific example, we explain the application of the three-story architecture, we build a small project to illustrate this problem. Sometimes for security, we usually encapsulate the connection with the database with a dynamic connection library file so that we should compile the write database .vb or .cs file into a dynamic connection library .dll file. Even we compile the relevant action page of the database into a .dll file.
Below is our main part of our database connection and operational file DBLINK.VB, the connection to the database:
DIM DBL AS SQLCONNECTION
For the operation of the database, we write it in a method and return the corresponding value:
Function getData () AS DataViewdim Scomm as SqlDataSetCommand
DIM SDS AS Dataset
DIM SSTR AS STRING
DBL = New SqlConnection ("Server = localhost; uid = sa; password =; database = howff")
SSTR = "SELECT * from color"
Scomm = New SqldatasetCommand (SSTR, DBL)
SDS = New DataSet ()
Scomm.FillDataSet (SDS, "Color")
Return SDS.Table ["color"]. DefaultView
END FUNCTION
Our sixth statement uses the connection variable of the database above. The function of our function is to select all the elements from the table "Color" and return to the form of the table structure. The complete code is as follows:
Imports system
Imports system.data
Imports system.data.sql
'Creating a namespace
Namespace DB
'Creating a class
Public Class Dblink
'Establish a database connection
DIM DBL AS SQLCONNECTION
'method
Public function getData () AS dataView
DIM Scomm as SqldatasetCommand
DIM SDS AS Dataset
DBL = New SqlConnection ("Server = localhost; uid = sa; password =; database = howff")
DIM SSTR AS STRING
SSTR = "SELECT * from color"
Scomm = New SqldatasetCommand (SSTR, DBL)
'Data input
SDS = New DataSet ()
Scomm.FillDataSet (SDS, "Color")
'return
Return SDS.Tables ("Color"). DefaultView
END FUNCTION
END CLASS
End Namespace
Let's write a front side to use the page Saidy.aspx, we must first introduce the namespace we created:
<% @ Import namespace = "db"%>
When loading, we use this method:
SUB Page_Load (Sender As Object, E as Eventargs)
'Creating a new object
Dim NewDB as dblink
Newdb = new dblink ()
'Data Sources
Products.DataSource = newdb.getdata ()
'Data binding
Products.DATABIND ()
End Sub
Let's take a look at our complete code (AdvanceApp / dblink.aspx):
<% @ Import namespace = "db"%>
