After I add a web service, I receive the following error: "An item with the same key has already been added" when trying to log into the configuration.

Question

After I add a web service, I receive the following error: "An item with the same key has already been added"  when trying to log into the configuration.

Answer

The situation might be caused by adding several source code schemas with equal namespace by a user. Delete the added service schemas from SysSchema and recompile the application by resetting:

update SysWorkspace set AssemblyData = null