I am trying to use a function in an unmanaged dll and I am getting a
System.NullReferenceException when called.

I do not have source code for the vendor dll.

WEBEXPORT    char*    function1;

vb.net
------
<DllImport("vendor.dll")> _
Public Shared Function function1() As <MarshalAs(UnmanagedType.LPStr)>
System.Text.StringBuilder
End Function
...
Dim sError As System.Text.StringBuilder
sError = waLastErrorStr()

I have tried calling by ordinal and several types for the return type
and nothing has worked so far.  There are several other functions in
this dll that I have been able to get to work successfully.  I have
also written some test code in c++ that also was able to successfully
call this function, but no luck so far in vb.net.

My guess so far is that the issue is because the function does not have
any parameters.  In c++ I have to call without () on the function call.
Is there any way to do that in vb.net?

Any thoughts?

Justin