Today I discovered an error in one of our CLR triggers in a SQL Server database:
System.Data.SqlClient.SqlException: A .NET Framework error occurred during execution of user-defined routine or aggregate "PersonalChangedTrigger": System.IO.FileLoadException: Could not load file or assembly 'System.Messaging, Version=126.96.36.199, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a' or one of its dependencies. Assembly in host store has a different signature than assembly in GAC. (Exception from HRESULT: 0x80131050) See Microsoft Knowledge Base article 949080 for more information.
This was kind of unexpected since we didn’t modify the trigger. It turns out that it was probably a Windows Update patch that modified the System.Messaging assembly so we had to “re-import” it into the database. This is how to do that, in our case:
ALTER ASSEMBLY Messaging FROM 'C:\WINDOWS\Microsoft.NET\Framework\v2.0.50727\System.Messaging.dll' WITH PERMISSION_SET = UNSAFE