How to: Create Unsigned Friend Assemblies (Visual Basic)

This example shows how to use friend assemblies with assemblies that are unsigned.

To create an assembly and a friend assembly

  1. Open a command prompt.

  2. Create a Visual Basic file named friend_signed_A. that contains the following code. The code uses the InternalsVisibleToAttribute attribute to declare friend_signed_B as a friend assembly.

    ' friend_unsigned_A.vb  
    ' Compile with:   
    ' vbc -target:library friend_unsigned_A.vb  
    Imports System.Runtime.CompilerServices  
    Imports System  
    <Assembly: InternalsVisibleTo("friend_unsigned_B")>   
    ' Friend type.  
    Friend Class Class1  
        Public Sub Test()  
        End Sub  
    End Class  
    ' Public type with Friend member.  
    Public Class Class2  
        Friend Sub Test()  
        End Sub  
    End Class  
  3. Compile and sign friend_signed_A by using the following command.

    vbc -target:library friend_unsigned_A.vb  
  4. Create a Visual Basic file named friend_unsigned_B that contains the following code. Because friend_unsigned_A specifies friend_unsigned_B as a friend assembly, the code in friend_unsigned_B can access Friend types and members from friend_unsigned_A.

    ' friend_unsigned_B.vb  
    ' Compile with:   
    ' vbc -r:friend_unsigned_A.dll friend_unsigned_B.vb  
    Module Module1  
        Sub Main()  
            ' Access a Friend type.  
            Dim inst1 As New Class1()  
            Dim inst2 As New Class2()  
            ' Access a Friend member of a public type.  
        End Sub  
    End Module  
  5. Compile friend_signed_B by using the following command.

    vbc -r:friend_unsigned_A.dll friend_unsigned_B.vb  

    The name of the assembly that is generated by the compiler must match the friend assembly name that is passed to the InternalsVisibleToAttribute attribute. You can explicitly set the assembly by using the /out compiler option.

  6. Run the friend_signed_B.exe file.

    The program displays two strings: "Class1.Test" and "Class2.Test".

.NET Framework Security

There are similarities between the InternalsVisibleToAttribute attribute and the StrongNameIdentityPermission class. The main difference is that StrongNameIdentityPermission can demand security permissions to run a particular section of code, whereas the InternalsVisibleToAttribute attribute controls the visibility of Friend types and members.

See also