[solved] OpenTK with WPF

public partial class MyGlUserControl : UserControl
    {
        bool loaded = false;
 
        public MyGlUserControl()
        {
            InitializeComponent();
        }
 
        Stopwatch sw = new Stopwatch();
        private void MyGlControl_Load(object sender, EventArgs e)
        {
            loaded = true;
            GL.ClearColor(Color.SkyBlue);
            SetupViewport();
        }
 
        private void MyGlControl_Resize(object sender, EventArgs e)
        {
            if (!loaded)
                return;
 
            SetupViewport();
            MyGlControl.Invalidate();
        }
 
        private void Render()
        {
            GL.Clear(ClearBufferMask.ColorBufferBit | ClearBufferMask.DepthBufferBit);
 
            GL.MatrixMode(MatrixMode.Modelview);
            GL.LoadIdentity();
 
            GL.Begin(BeginMode.Triangles);
            GL.Color3(Color.Yellow);
            GL.Vertex2(10, 20);
            GL.Vertex2(100, 20);
            GL.Vertex2(100, 50);
 
            GL.End();
 
            MyGlControl.SwapBuffers();
            //MyGlControl.Invalidate();
        }
 
        private void MyGlControl_Paint(object sender, PaintEventArgs e)
        {
            if (!loaded)
                return;
 
            Render();            
        }
 
        private void SetupViewport()
        {
            int w = MyGlControl.Width;
            int h = MyGlControl.Height;
            GL.MatrixMode(MatrixMode.Projection);
            GL.LoadIdentity();
            GL.Ortho(0, w, 0, h, -1, 1); //Bottom left corner pixel has corrdinate 0,0
            GL.Viewport(0, 0, w, h); //Use all of the MyGlControl painting area
        }
    }