What is this exception ?

Question

I am getting this exception while reading the shapes in excel sheet in c#: on code line of

if (worksheet.Shapes.Count >= iCurrentRowIndex)
{ }

Unable to cast COM object of type 'System.__ComObject' to interface type 'Microsoft.Office.Interop.Excel._Worksheet'. This operation failed because the QueryInterface call on the COM component for the interface with IID '{000208D8-0000-0000-C000-000000000046}' failed due to the following error: The application called an interface that was marshalled for a different thread. (Exception from HRESULT: 0x8001010E (RPC_E_WRONG_THREAD)).

Edited:

This application locally running perfect but when i deploy it on IIS , it throws exception. What should the reason? I use code for thread as

string strImageSavedPath = string.Empty;
ThreadStart cbThreadStater = delegate { strImageSavedPath =  CopyToClipBoard(worksheet, (int)iRowindex, strApplicationPath); };
Thread thrd = new Thread(cbThreadStater);
thrd.SetApartmentState(ApartmentState.STA);
thrd.Start();
thrd.Join(); 

Where CopyToClipBoard method reads the image of supplied row index, saves the image in file system and return the path.

System.InvalidCastException was unhandled Message="Unable to cast COM object of type 'System.__ComObject' to interface type 'Microsoft.Office.Interop.Excel._Worksheet'. This operation failed because the QueryInterface call on the COM component for the interface with IID '{000208D8-0000-0000-C000-000000000046}' failed due to the following error: The application called an interface that was marshalled for a different thread. (Exception from HRESULT: 0x8001010E (RPC_E_WRONG_THREAD))." Source="Microsoft.Office.Interop.Excel" StackTrace: at Microsoft.Office.Interop.Excel._Worksheet.get_Shapes() at KGD6ExcelReader.ExcelManager.CopyToClipBoard(Worksheet worksheet, Int32 iRowindex, String strApplicationPath) in D:\ParallelMinds\Shared\KGD6ExcelReader\KGD6ExcelReader\ExcelManager.cs:line 522 at KGD6ExcelReader.ExcelManager.<>c_DisplayClass3.b_0() in D:\ParallelMinds\Shared\KGD6ExcelReader\KGD6ExcelReader\ExcelManager.cs:line 376 at System.Threading.ThreadHelper.ThreadStart_Context(Object state) at System.Threading.ExecutionContext.runTryCode(Object userData) at System.Runtime.CompilerServices.RuntimeHelpers.ExecuteCodeWithGuaranteedCleanup(TryCode code, CleanupCode backoutCode, Object userData) at System.Threading.ExecutionContext.RunInternal(ExecutionContext executionContext, ContextCallback callback, Object state) at System.Threading.ExecutionContext.Run(ExecutionContext executionContext, ContextCallback callback, Object state) at System.Threading.ThreadHelper.ThreadStart() InnerException:

Answer 1

Is the code running on a background thread? If so, you need to set the ApartmentState for the thread to STA - you'll have to new up an actual Thread to do this and call the SetApartmentState method.

http://goo.gl/elyd for more on that.

Answer 2

The COM interface reference (probably worksheet) that you are trying to use is for a proxy that is in a different appartment to the current thread. See link text.

Try marshalling the reference to the current thread.