Variable has a survival cycle
This programmer knows that a modified shared is added to VB.NET. Shared Keywords Indicates one or more declared programming elements will be shared. The point is: the shared element is not a particular instance of a certain or structure. It is necessary to qualify the shared element to access them by using the variable name of the specific instance of the class name or structure name or a specific instance of the class or structure. A simple description is that the Shared variable is for type itself instead of serving a specific object.
Shared example
Public Class Testa
Public Shared I as INT32 = 10
END CLASS
Public Class TestB
Inherits Testa 'inherits Testa
Public Sub New ()
Testa.i = 100 'uses the name of the name to access Shared variables
End Sub
END CLASS
It should be noted that the relationship between Shared variables and types and instances in VB.NET requires not particularly strict syntax, and the programmer can use the type of instance to access and modify the shared variable, but it is very strict in C #. .
Assigning statement
Assign the value in VB.NET divided into: Simple assignment statement, composite assignment statement, delegate assignment statement, MID assignment statement.
Simple assignment statement
Simple assignment statements and previous VB assignment statements are basically not very different, but now VB.NET allows immediate assignments to the variable declaration (examples can be seen in front of the front accessibility). We need to pay attention to the declarations and assignment methods of arrays.
In VB.NET, you can describe the latitude and upper limits of the array when declaring array, and the lower limit of the latitude of each array is 0, and cannot be changed. However, "zero length array" can be specified by specifying the upper limit of the array as -1. This array does not contain any elements.
If you do not display the length of the array, you can assign a value immediately on the declaration array.
An array of statements and assignments
Public Class Testa
DIM IARR () AS INT32
DIM Barr (5) as boolean '5 refers to the upper limit of the Barr subscript, that is, 6 elements
Dim larr () as long = new long (3) {100, 200, 300, 400}
DIM Carr () as string = new string () {"a", "b", "c"}
DIM DARR (-1) As Double
END CLASS
About more characteristics of the array, will be described in detail in the introduction of the array.
Composite assignment
Now VB.NET begins to support composite assignment statements. Unlike the fully expanded expression, the variable on the left side of the composite assignment statement is only calculated once. This means that at runtime, the variable expression is calculated on the right side of the right side of the assignment statement.
Composite assignment
Public Class Testa
Public Sub New ()
DIM I as Int32
i = 10
End Sub
END CLASS
MID assignment
The MID assignment is actually the processing assignment process of the string. A method of assignment of the MID can be understood by the following examples.
MID example
Public Class Testa
Public Sub New ()
DIM TMPSTR AS STRING
Tmpstr = "Hello VB.NET" 'Hello VB.NET
MID (Tmpstr, 7, 2) = "c #" 'Hello C # .NET
MID (tmpstr, 7) = "VB6" 'Hello VB6NET
MID (Tmpstr, 7) = "VB6 to VB.NET" 'Hello VB6 TO
MID (Tmpstr, 7, 3) = "VB6 to VB.NET" 'Hello VB6 TOEND SUB
END CLASS
Keywords on the entrusted statement
Addressof
A detailed description is described in later commission and events.
