I was struggling with this error for a few days . It came out after I’ve upgraded my project to Visual Studio 2012.
Unable to cast COM object of type ‘System.__ComObject’ to interface type ‘Microsoft.Office.Interop.Excel.Application’. This operation failed because the QueryInterface call on the COM component for the interface with IID ‘{000208D5-0000-0000-C000-000000000046}’ failed due to the following error: Error loading type library/DLL. (Exception from HRESULT: 0x80029C4A (TYPE_E_CANTLOADLIBRARY)).
It shows up while it’s the time for Excel operations:
Workaround:
It occurs because I’ve installed Office 2013 instead of Office 2010 which I was using with old version of my project. After I upgraded my Office, the project was no longer able to link Excel reference.
Even though I referenced new Excel library which is 15.0, it didn’t work.
Solution:
- Delete the Excel reference (Microsoft.Office.Interop.Excel). Version 15.0, in my case.
- Install Microsoft Excel (whichever version you had been using. Version 2010 for me)
- Add the Excel reference (older one. Version 14.0, in my case)
Long story short: Never take more than one risk at the same time!