How to: Create Signed Friend Assemblies (Visual Basic)
This example shows how to use friend assemblies with assemblies that have strong names. Both assemblies must be strong named. Although both assemblies in this example use the same keys, you could use different keys for two assemblies.
To create a signed assembly and a friend assembly
Open a command prompt.
Use the following sequence of commands with the Strong Name tool to generate a keyfile and to display its public key. For more information, see Sn.exe (Strong Name Tool)).
Generate a strong-name key for this example and store it in the file FriendAssemblies.snk:
sn -k FriendAssemblies.snk
Extract the public key from FriendAssemblies.snk and put it into FriendAssemblies.publickey:
sn -p FriendAssemblies.snk FriendAssemblies.publickey
Display the public key stored in the file FriendAssemblies.publickey:
sn -tp FriendAssemblies.publickey
Create a Visual Basic file named
friend_signed_Athat contains the following code. The code uses the InternalsVisibleToAttribute attribute to declare friend_signed_B as a friend assembly.
The Strong Name tool generates a new public key every time it runs. Therefore, you must replace the public key in the following code with the public key you just generated, as shown in the following example.
' friend_signed_A.vb ' Compile with: ' Vbc -target:library -keyfile:FriendAssemblies.snk friend_signed_A.vb Imports System.Runtime.CompilerServices <Assembly: InternalsVisibleTo("friend_signed_B, PublicKey=0024000004800000940000000602000000240000525341310004000001000100e3aedce99b7e10823920206f8e46cd5558b4ec7345bd1a5b201ffe71660625dcb8f9a08687d881c8f65a0dcf042f81475d2e88f3e3e273c8311ee40f952db306c02fbfc5d8bc6ee1e924e6ec8fe8c01932e0648a0d3e5695134af3bb7fab370d3012d083fa6b83179dd3d031053f72fc1f7da8459140b0af5afc4d2804deccb6")> Public Class Class1 Public Sub Test() System.Console.WriteLine("Class1.Test") System.Console.ReadLine() End Sub End Class
Compile and sign friend_signed_A by using the following command.
Vbc -target:library -keyfile:FriendAssemblies.snk friend_signed_A.vb
Create a Visual Basic file that is named
friend_signed_Band contains the following code. Because friend_signed_A specifies friend_signed_B as a friend assembly, the code in friend_signed_B can access
Friendtypes and members from friend_signed_A. The file contains the following code.
' friend_signed_B.vb ' Compile with: ' Vbc -keyfile:FriendAssemblies.snk -r:friend_signed_A.dll friend_signed_B.vb Module Sample Public Sub Main() Dim inst As New Class1 inst.Test() End Sub End Module
Compile and sign friend_signed_B by using the following command.
vbc -keyfile:FriendAssemblies.snk -r:friend_signed_A.dll friend_signed_B.vb
The name of the assembly generated by the compiler must match the friend assembly name passed to the InternalsVisibleToAttribute attribute. You can explicitly set the assembly by using the
-outcompiler option. For more information, see -out (Visual Basic).
Run the friend_signed_B.exe file.
The program displays the string "Class1.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.