Error in CLR assembly after migrating to SQL server 2012

Question

We moved to SQL Server 2012 from 2008R2 and I am unable to get the CLR assembly working.  I have read several topics about trustworthy setting and a mismatch dbo SID. I checked the SID and everything looks good and the 2008R2 server works fine with
Trustworthy set to OFF.  I'm starting to think it is a .NET issue.  2008R2 works with 2.0 and 2012 uses 4.0 and i'm wondering if just redeploying the assembly will fix the problem.  Any suggestions would be greatly appreciated. 
Msg 10314, Level 16, State 11, Procedure MP_ExportXYToCSV2, Line 41
An error occurred in the Microsoft .NET Framework while trying to load assembly id 65540. The server may be running out of resources, or the assembly may not be trusted with PERMISSION_SET = EXTERNAL_ACCESS or UNSAFE. Run the query again, or check documentation
to see how to solve the assembly trust issues. For more information about this error:
System.IO.FileLoadException: Could not load file or assembly 'exporttocsv, Version=1.0.4780.25878, Culture=neutral, PublicKeyToken=f5567e386ca8280d' or one of its dependencies. An error relating to security occurred. (Exception from HRESULT: 0x8013150A)
System.IO.FileLoadException:
   at System.Reflection.RuntimeAssembly._nLoad(AssemblyName fileName, String codeBase, Evidence assemblySecurity, RuntimeAssembly locationHint, StackCrawlMark& stackMark, IntPtr pPrivHostBinder, Boolean throwOnFileNotFound, Boolean forIntrospection,
Boolean suppressSecurityChecks)
   at System.Reflection.RuntimeAssembly.InternalLoadAssemblyName(AssemblyName assemblyRef, Evidence assemblySecurity, RuntimeAssembly reqAssembly, StackCrawlMark& stackMark, IntPtr pPrivHostBinder, Boolean throwOnFileNotFound, Boolean forIntrospection,
Boolean suppressSecurityChecks)
   at System.Reflection.RuntimeAssembly.InternalLoad(String assemblyString, Evidence assemblySecurity, StackCrawlMark& stackMark, IntPtr pPrivHostBinder, Boolean forIntrospection)
   at System.Reflection.RuntimeAssembly.InternalLoad(String assemblyString, Evidence assemblySecurity, StackCrawlMark& stackMark, Boolean forIntrospection)
   at System.Reflection.Assembly.Load(String assemblyString)

Answer 1

It is not clear what you have done, for an assembly with a permission set beyond SAFE to work, one of these conditions must be set:
1) The database is trustworthy and the database owner has EXTERNAL ACCESS ASSEMBLY or UNSAFE ASSEMBLY permission, depending on the permission set for the assembly.
2) The assembly is a signed with a key, and that key exists in the master database. A login has been created from the key, and this login has been granted the matching assembly permission.
Since you say that it worked on SQL 2008 R2 without trustworthy, I would assume that you had a key-login pair on the old server, but forgot to move them to the new server.
Don't set the database trustworthy. This is a potential security risk.
Erland Sommarskog, SQL Server MVP, [email protected]