What debug messages are you getting ? If it's not rendering you should be getting error message. You can always download PIX if you are really desperate to have a look at the graphics state and resources.

Are you a C++ programmer ? Or perhaps just too strictly following those tutorials. Because setting all your variables to null isn't necessary in C#. It's not a problem but it's not necessary, a simple declaration is sufficient ...

private SlimDX.Direct3D11.Texture2D textureD3D11;

What debug messages are you getting ? If it's not rendering you should be getting error message. You can always download PIX if you are really desperate to have a look at the graphics state and resources.