OpenGl.GL.SupportsExtension

The problem was that OpenGL 3.x changed the way to query extensions. Instead of using hacks to guess which OpenGL profile is being used (2.1, 3.0/3.1 compatible/forward-compatible, 3.2 core/compatibility), it's easier to move this to user code which already knows what version is being used. For example, if you are using 1.1-2.1 or 3.x compatibility, you can use GL.GetString(StringName.Extensions).Contains("foo"). For 3.x core, you'll have to iterate through available extensions using GL.GetString(StringName.Extensions, i).

GL.SupportsFunction cannot be supported cleanly now that it is possible to create multiple OpenGL contexts (that wasn't a consideration when the function was first introduced). Right now, the same functionality can be achieved with this extension method:

static class GraphicsContextExtensions
{
    public static bool SupportsFunction(this IGraphicsContextInternal context)
    {
        if (context == null)
            throw new ArgumentNullException("context");
        return context.GetAddress("foo") != IntPtr.Zero;
    }
}

but I think this should be added directly to IGraphicsContext.