Q: Error while accessing DLL interface from Web Application I have made one windows Form application in C#. I have added one DLL reference in that application and called method of that DLL. Its working fine. But when I have made web application and added reference of same DLL and tried to run then I am getting error as 
Unable to cast COM object of type 'XXXXX.XXXX' to interface type 'XXXXX.XXXX'. 
This operation failed because the QueryInterface call on the COM component for the interface with IID '{2DEEB1D7-0B44-4142-9E7B-07477781696C}' failed due to the following error: Bad variable type. (Exception from HRESULT: 0x80020008 (DISP_E_BADVARTYPE)).

The method in DLL, I am calling from web application as
m_SSCP.StartUp("FilePath", "value1", "value2", 6553703, 0, out return_code);

So if I am calling same function from Web application and Windows form application, Is there any difference between these two operation?
I tried to search on net but I am not getting any proper help. 
