VB.Net - Directives

Module mydirectives
#Const age = True
Sub Main()
   #If age Then
      Console.WriteLine("You are welcome to the Robotics Club")
   #End If
   Console.ReadKey()
End Sub
End Module

When the above code is compiled and executed, it produces the following result −

You are welcome to the Robotics Club

The #ExternalSource Directive

This directive is used for indicating a mapping between specific pnes of source code and text external to the source. It is used only by the compiler and the debugger has no effect on code compilation.

This directive allows including external code from an external code file into a source code file.

Syntax for this directive is −

#ExternalSource( StringLiteral , IntLiteral )
   [ LogicalLine ]
#End ExternalSource

The parameters of #ExternalSource directive are the path of external file, pne number of the first pne, and the pne where the error occurred.

Example

The following code demonstrates a hypothetical use of the directive −

Module mydirectives
   Pubpc Class ExternalSourceTester

      Sub TestExternalSource()

      #ExternalSource("c:vbprogsdirectives.vb", 5)
         Console.WriteLine("This is External Code. ")
      #End ExternalSource

      End Sub
   End Class

   Sub Main()
      Dim t As New ExternalSourceTester()
      t.TestExternalSource()
      Console.WriteLine("In Main.")
      Console.ReadKey()

   End Sub

When the above code is compiled and executed, it produces the following result −

This is External Code.
In Main.

The #If...Then...#Else Directives

This directive conditionally compiles selected blocks of Visual Basic code.

Syntax for this directive is −

#If expression Then
   statements
[ #ElseIf expression Then
   [ statements ]
...
#ElseIf expression Then
   [ statements ] ]
[ #Else
   [ statements ] ]
#End If

For example,

#Const TargetOS = "Linux"
#If TargetOS = "Windows 7" Then
     Windows 7 specific code
#ElseIf TargetOS = "WinXP" Then
     Windows XP specific code
#Else
     Code for other OS
#End if

Example

The following code demonstrates a hypothetical use of the directive −

Module mydirectives
#Const classCode = 8

   Sub Main()
   #If classCode = 7 Then
      Console.WriteLine("Exam Questions for Class VII")
   #ElseIf classCode = 8 Then
      Console.WriteLine("Exam Questions for Class VIII")
   #Else
      Console.WriteLine("Exam Questions for Higher Classes")
   #End If
      Console.ReadKey()

   End Sub
End Module

Exam Questions for Class VIII

#Region "identifier_string" 
#End Region

#Region "StatsFunctions" 
     Insert code for the Statistical functions here.
#End Region