I am using Excel Interop in a SSIS Script task on a server with Excel 2007 installed.
Since a few days, errors appear when I try to open the script task. Whenever I open the code, the references to Interop are marked with a yellow warning sign and the namespace cannot be referenced. I cannot add it again via "Add References", and when I try to add Excel Object Library in the COM Tab, it is also added with yellow warning signs (I couldn't find an error message for that).
However, when I don't save the changes and just run the whole project, it works without problems. Interop therefore seems to work, but it is somehow not found in Visual Studio. I tried to install the PrimaryInteropAssemblies again, without success. The interop assembly is still found under c:\windows\assembly. The strange thing there is, that there is no processor architecture given for the assembly, while it is on my development machine. I tried to uninstall the assembly to then install it again, but couldn't do it due to insufficient rights (even as administrator).
I had to install the Windows SDK a few days ago to use gacutil, could that be the reason for the missing reference?
The programming language is C# 2010 with Visual Studio 2010.
Thanks,
EDIT: I found a solution, although it still doesn't work as it is supposed to be. Here is how it works: The problem can be solved by setting the "specified version" property of the reference to false. New projects can use the interop by referencing to it under C:\Windows\assembly\GAC\Microsoft.Office.Interop.Excel\12.0.0.0__71e9bce111e9429c\Microsoft.Office.Interop.Excel.dll
