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This article mainly shows you "what are the VB.NET variable scope rules", the content is easy to understand, clear, hope to help you solve your doubts, the following let the editor lead you to study and learn "what are the VB.NET variable range rules" this article.

How does the VB.NET programming language make us feel different? We can experience this change through a change in the range of variables. Defining the scope of VB.NET variables in a program is different from defining it in VB 6. In VB 6, variables defined anywhere in a program can be used throughout the program.

In VB.NET, variables defined in a subroutine can only be used in that subroutine (a subroutine is the code contained within these statements such as If...End If,For...Next,Select Case...End Select,Do...Loop. ).

This difference allows you to write code that is more stylized and flexible, while preventing variables from being called by programs that are not supposed to be within their scope.

But the drawback of this change is that each range of VB.NET variables keeps its value the same throughout the program. That is, when a variable is beyond its scope, its value is still stored in memory. If you enter the same subroutine again in the program, the previously stored value of this variable in memory may cause a potential error.

For instance. Take a look at the following code:

Dim x As Integer = 1 Dim holdY As Integer Do While (x < 5) If (x Mod 2 = 0) Then Dim y As Integer y + = 1 holdY = y End If x + = 1 Loop MsgBox (x) MsgBox (holdY)

After the above code runs, the value of x is 5 and the value of HoldY is 3. The application of the value of y is limited to the whole Do...Loop process.

Initializing a variable when defining the scope of a VB.NET variable is a direct solution, it avoids any potential problems and ensures that the value of the variable is known each time it is used.

If (x Mod 2 = 0) Then Dim y As Integer = 0 y + = 1

Another benefit is that initializing variables in the definition makes the code more readable.

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