"An error occurred while signing: Key not valid for use in specified state" when compiling Outlook 2010 add-in

Question

I'm building an Outlook 2010 add-in that will tie into our ticketing system using the ticket systems' API. A week ago I was able to compile and get context/ribbon menus which executed their functions properly. This morning I added some functions to encrypt and decrypt the API key, but now when I try to compile I get

"Error 1 An error occurred while signing: Key not valid for use in specified state."

There is no line number or file associated with the error. At first I thought it was something with the System.Security class I had included, but commenting out everything associated with that and removing the reference to System.Security did not fix the problem.

I have tried restarting everything and doing a clean build with no luck. On the advise of this forum post I have tried deleting both my machine and local RSA files but that made no difference. I have also tried deleting the _TemporaryKey.pfx file in my solution in the hopes that if that were having issues that VS would recreate a new working one, but that didn't even change the error message to tell me the file was missing.

After all this I tried opening a different add-in project that I hadn't modified for about a week and it too had the same error. I'm not sure at this point if it is a problem with Visual Studio or my computer but a brand new Outlook add-in project will compile successfully so it is only affecting old projects.

Answer 1

Creating a new test certificate seems to have solved the problem. This blog post pointed me in the right direction.

• Open the properties page for the project that is giving the error.
• Click the Signing tab.
• Click Create Test Certificate.
• Enter a password and click OK.

This got things working again for me.