Using OpenGl with C#?

OpenTK is an improvement over the Tao API, as it uses idiomatic C# style with overloading, strongly-typed enums, exceptions, and standard .NET types:

GL.Begin(BeginMode.Points);
GL.Color3(Color.Yellow);
GL.Vertex3(Vector3.Up);

as opposed to Tao which merely mirrors the C API:

Gl.glBegin(Gl.GL_POINTS);   // double "gl" prefix
Gl.glColor3ub(255, 255, 0); // have to pass RGB values as separate args
Gl.glVertex3f(0, 1, 0);     // explicit "f" qualifier

This makes for harder porting but is incredibly nice to use.

As a bonus it provides font rendering, texture loading, input handling, audio, math...

Update 18th January 2016: Today the OpenTK maintainer has stepped away from the project, leaving its future uncertain. The forums are filled with spam. The maintainer recommends moving to MonoGame or SDL2#.

Update 30th June 2020: OpenTK has had new maintainers for a while now and has an active discord community. So the previous recommendation of using another library isn't necessarily true.

I think what @korona meant was since it's just a C API, you can consume it from C# directly with a heck of a lot of typing like this:

[DllImport("opengl32")]
public static extern void glVertex3f(float x, float y, float z);

You unfortunately would need to do this for every single OpenGL function you call, and is basically what Tao has done for you.

Tao is supposed to be a nice framework.

From their site:

The Tao Framework for .NET is a collection of bindings to facilitate cross-platform media application development utilizing the .NET and Mono platforms.

I would also recommend the Tao Framework. But one additional note:

Take a look at these tutorials: http://www.taumuon.co.uk/jabuka/

What would you like these support libraries to do? Just using OpenGL from C# is simple enough and does not require any additional libraries afaik.

XNA 2.0 requires a minimum of a shader 1.1 card. While old tech, not everyone has one. Some newer laptops (in our experience Toshiba tablets with Intel graphics) have no shader 1.1 support. XNA simply wont run on these machines.

This is a significant issue for us and we have shifted to Tao and OpenGL. Plus with Tao we have bindings for audio & Lua support.