VisualBasic.Net unable to see Managed functions returning char*

While working in a managed-unmanaged thing in VC++.Net,
I had created an unmanaged (static) function then in the managed (__gc) class I called that function and exposed it through this managed class.

I then tried to call that managed function returning char* or an ansi-string but My visual basic .net was unable to see that function from the managed class, and it was able to see other functions that are returning int or other type at the same time.
To check the things I then created a C# project and called that dll created by vc++.net and I was able to see and call the function that returns char*, only thing I needed was to apply the conversion of string from ansi to 2-byte string (unicode).