I developed a new Office 2007 addin using VS 2008 and VSTO. after this I go to
Office->Excel Options->AddIns->COM AddIns and GO… If I select the .dll which I ve created I get the error
'<path>' is not a valid Office Add In.
If I run it using the Visual Studio 2008 at my development machine, it works fine and I see the add-in.
I searched so many posts but didn't get a solution.
Best Answer
Excel kept rejecting the Add-In, so the solution for me was doing it directly via the registry.
Save the below text as a .reg file, replace the Manifest path and FriendlyName to suit your PROJECT and double click the reg file to add the key to the Registry.