c# - SQL Server: "CREATE ASSEMBLY for assembly 'Test' failed because assembly 'Test' is malformed or not a pure .NET assembly."

Question

I get this error when I attempt to load a mixed mode C++/CLI assembly into SQL Server 2012:

CREATE ASSEMBLY [Test]
AUTHORIZATION [dbo]
from 'H:est.dll'
WITH PERMISSION_SET = SAFE

Msg 6544, Level 16, State 1, Line 1 CREATE ASSEMBLY for assembly 'Test' failed because assembly 'Test.dll' is malformed or not a pure .NET assembly. Unverifiable PE Header/native stub.

Answer 1

It is impossible to load a mixed mode C++/CLI assembly into SQL Server.

You can only load a "pure" C++/CLI assembly:

However, there may be a way around this. Use P/Invoke in your C# file. This is equivalent to writing a mixed mode C++/CLI assembly wrapper, because when CLR code calls native code in your assembly, it performs an implicit P/Invoke (let me know if this works for you).

Why does SQL server prevent mixed mode assemblies from being loaded?

This is my theory:

If we go back to 2005, things were different. When they released the first version of SQL Server to support the CLR, mixed mode assemblies would sometimes deadlock on a load. See Microsoft - Mixed DLL Loading Problem. Even after they fixed this issue, there was still arguments centered around security and stability which tipped the scales against allowing loading of mixed mode C++/CLI assemblies into the core of SQL server.

If anyone on the original Microsoft design team can fill in the blanks, I'd be very curious!