VB.Net 教程：Nested If 嵌套If语句

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在VB.Net中总是合法的嵌套If-Then-Else语句，这意味着您可以在另一个If ElseIf语句中使用一个If或ElseIf语句。

语法：

If( boolean_expression 1)Then
   'Executes when the boolean expression 1 is true 
   If(boolean_expression 2)Then
         'Executes when the boolean expression 2 is true 
   End If
End If

您可以嵌套ElseIf … Else的方式，与嵌套If语句类似。

示例：

Module decisions
   Sub Main()
      'local variable definition
      Dim a As Integer = 100
      Dim b As Integer = 200
      ' check the boolean condition 
      If (a = 100) Then
          ' if condition is true then check the following 
          If (b = 200) Then
              ' if condition is true then print the following 
              Console.WriteLine("Value of a is 100 and b is 200")
          End If
      End If
      Console.WriteLine("Exact value of a is : {0}", a)
      Console.WriteLine("Exact value of b is : {0}", b)
      Console.ReadLine()
   End Sub
End Module

当上述代码被编译和执行时，它产生以下结果：

Value of a is 100 and b is 200
Exact value of a is : 100
Exact value of b is : 200

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