Tlbexp.exe and Regasm.exe (.NET FrameWork Tools Series)

Introduction

TlbExp.exe and Regasm.exe tools aid us in exporting assembly information to a type library so that non .NET Applications or unmanaged code use this type library information to call .NET assembly.

Just like tlbimp which works on the entire COM Component tlbexp works on the entire assembly.

The entire assembly is converted at the same time. You cannot use it to generate type information for a subset of the types.

Tbexp only generates the type library information for an assembly but it does not register the type libraries unlike regasm.exe

Let us now create an assembly for which we will create a type library and use it through Visual Basic.

1. Open a new dotnet project (Class Library)
2. Add a class to the project called MyClass as below

   public class MyClass
   {
       public MyClass()
       {
       }
       public int Add (int i , int j)
       {
           return i +j;
       }
       public int Mul (int i , int j)
       {
           return i *j;
       }
   }

3. Strong name your assembly, compile the project and create the assembly
4. Go to the Visual Studio command prompt and type tlbexp /? to explore all the options. I have enlisted them below:

   /out:FileName           File name of type library to be produced
   /nologo                 Prevents TlbExp from displaying logo
   /silent                 Prevents TlbExp from displaying success message
   /verbose                Displays extra information
   /names:FileName         A file in which each line specifies the 
                           captialization of a name in the type library.
   /? or /help             Displays this usage message

5. To create a typelibrary from it type the following command tlbexp <application name>.dll e.g. tlbexp tlbexp.dll
6. If the export was successful a success message diplaying the entire path and the name of the .tlb will be shown to you

   Assembly exported to F:\Net\tlbexp\bin\Debug\tlbexp.tlb

7. You can also use the /verbose option to check out the details of the classes that were exported
8. Although our typelibrary is created, our assembly is not yet registered. You can register the assembly using regasm tool
9. Go to the Visual Studio command prompt and type regasm /? to explore all the options. I have enlisted them below:

   /unregister         Unregister types
   /tlb[:FileName]     Export the assembly to the specified type library 
                       and register it
   /regfile[:FileName] Generate a reg file with the specified name 
                       instead of registering the types. 
                       This option cannot be used with 
                       the  /u or /tlb options
   /codebase           Set the code base in the registry
   /registered         Only refer to already registered type libraries
   /nologo             Prevents RegAsm from displaying logo
   /silent             Silent mode. Prevents displaying of success messages
   /verbose            Displays extra information
   /? or /help         Display this usage message
   

10. To only register the assembly, use the following command:

    regasm <application name>.dll    e.g. regasm TlbExp.dll 

11. You can also create a .reg file containing all the registry entries:

    regasm TlbExp.dll  /regfile:myTlbExp.dll .reg

12. You also create typelibrary from assembly using regasm tool by using /tlb option
13. To use this component from VB 6.0 put the assembly in GAC. You can do this by either using gacutil or just dragging and dropping the assembly in <drive>/winnt/assembly folder
14. You can now use this assembly from VB 6.0
15. Open a VB std project. Go to references. Select the .tlb file that we generated from the list
16. Yes, you can now use your .NET assembly from VB 6.0. The sample code of using your .NET assembly from VB:

    Dim tlbExp As tlbExp.MyClass
    Set tlbExp = New tlbExp.MyClass
    Label1.Caption = tlbExp.Add(1, 2)

Note : You cannot use tlbexp on an assembly produced by tlbimp because in that case you can directly use type library which was used to produce the assembly.