queryinterface for interface failed

Question

I'm using an interop COM assembly in my 1.1 VB.NET code, and when I try to set a property of a class, I get an InvalidCastException with the message "QueryInterface for Interface … failed."

Any ideas on this?

Answer 1

First, make sure your COM component is registered with regsvr32.exe.

Then, make sure any necessary marshalling support is also registered -- these come in one of two kinds:

1) proxy/stub DLL, usually called <YourComponent>ps.dll -- register this too with regsvr32.exe

2) Associated type library -- register this with regtlib.exe

If you used tlbimp on your DLL, try using regtlib to register the DLLs type library.