Enable only early binding for COM classes in C#

Question

I'm creating classs library by using C# that will be used from VBA. But one thing discurages me - when I delete or change some letters in a method name and try to compile vba project then I get no errors. But I want to get compile error message if As I found out it happens because of using late binding.

I'll try to explain.

It is correct signature:

Sub Test()
  Dim cls as New SomeClass
  cls.SomeMethod
End Sub

It is signature with misspelling:

Sub Test()
  Dim cls as New SomeClass
  cls.**SomeMetod**
End Sub

Press Compile VBA Project - everything is ok, but it shouldn't be.

I've changed base interface as shown below:

[Guid("Some GUID here"), InterfaceType(ComInterfaceType.InterfaceIsIUnknown)]
public interface IComInterface
{}

and base class:

[ClassInterface(ClassInterfaceType.None)]
public class BaseClass

But nothing happens!!! I only get errors at runtime.

Then don't use late binding. Add the type library in whatever vba tool you are using. — Hans Passant
"Then don't use late binding" - I don't know how to make my classes using early binding — frippy
You cannot get a step-by-step answer until you explain what vba-enabled program you are using. If this is actually VBScript then early binding is not possible. — Hans Passant

frippy frippy · Accepted Answer · 2012-10-12T10:07:01

Solution is:

    [Guid("Some GUID here"), InterfaceType(ComInterfaceType.InterfaceIsIUnknown)]
    public interface IComInterface
    {}

and base class:

    [ClassInterface(ClassInterfaceType.AutoDual)]
    public class BaseClass

Be aware that versioning of your code will be not supported! Also .NET methods like ToString(), GetHashCode() etc became visible in VBA. So you will need to use attribute [ComVisible(false)] for these methods. This will work for ToString, GetHashCode, Equals. GetType impossible to hide in that case. So you need to decide wether you need to hide .NET methods or have early binding and complation warnings

Enable only early binding for COM classes in C#

1 Answers