SQLCLR using the wrong version of the .NET Framework

Question

During a recent restart of our development server the SQL Server started using .NET 4.0 for the SQLCLR. This means that nothing using the CLR in SQL works, or at least that's my understanding by reading these sources:

http://software.intel.com/en-us/blogs/2009/10/16/sql-server-2008-sqlclr-net-framework-version/

www.sqlskills.com/BLOGS/BOBB/post/On-SQL-Server-and-NET-40.aspx

All we get are error messages of this type:

Msg 6517, Level 16, State 1, Line 1 Failed to create AppDomain "xxx.dbo[ddl].3". Method's type signature is not Interop compatible.

Running the statement (as suggested by @john-christensen)

select * from sys.dm_clr_properties

results in the following information:

*Name*      *Value*
directory   C:\Windows\Microsoft.NET\Framework64\v4.0.30319\
version     v4.0.30319
state       CLR is initialized

Does anyone know how to solve this or how we can force SQL Server CLR to use an earlier version of the Framework?

Answer 1

I experienced the same annoying problem. None of the Geography/Geometry stuff in my database worked. Took me some unsuccesfull reinstalls of SQL server to finally (some weeks later!) find the following key in my registry had been set to '1'

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\.NETFramework\OnlyUseLatestCLR

when I reset it to '0', and rebooted the machine, things worked again!

Hans

Answer 2

Typically you can force a .NET application to use a specific .NET Framework version by specifying the supportedRuntime tag in the application's config file.

So you could try creating a sqlservr.exe.config in the \Binn folder under the root path of the SQL instance and specify there that you would like to use only .NET versions up to 3.5. Check this MSDN link for the structure of the config file.

Answer 3

From the article and my research on the web, it looks like the opposite might be happening - could you potentially be registering a 4.0 DLL? It appears that SQL Server 2008 will always load the 2.0 CLR and not the 4.0 CLR. Try running this statement, it will tell you what version your SQL server is running:

select * from sys.dm_clr_properties