Can't draw a Line and a point with c# Tao.OpengGL

Question

Using Tao.Freeglut and Tao.OpenGl. I tried to create some points by typing this code.

But when I run it, it show only a white windows but didn't have any points on it. Did someone know how to fix this problem.( same problem when i try to use GL_LINES with 2 points)

using Tao.Freeglut;
using Tao.OpenGl;

 public static void init()
        Gl.glClearColor(1.0f, 1.0f, 1.0f, 0.0f);
        Gl.glColor3f(0.0f, 0.0f, 1.0f);
        Gl.glPointSize(4);
        Gl.glMatrixMode(Gl.GL_PROJECTION);
        Gl.glLoadIdentity();
        Glu.gluOrtho2D(0.0, 400, 0.0, 300.0);

    }

    public static void myDisplay()
    {

        Gl.glClear(Gl.GL_COLOR_BUFFER_BIT);
        Gl.glBegin(Gl.GL_POINT);
        {
            Gl.glVertex2i(50, 50);
            Gl.glVertex2i(100, 100);
            Gl.glVertex2i(100, 150);
            Gl.glVertex2i(200, 200);
            Gl.glVertex2i(200, 250);
            Gl.glEnd();
        }
        Gl.glFlush();
    }

    static void Main()
    {
        Glut.glutInit();
        Glut.glutInitDisplayMode(Glut.GLUT_SINGLE | Glut.GLUT_RGB);
        Glut.glutInitWindowPosition(50, 100);
        Glut.glutInitWindowSize(400, 300);
        Glut.glutCreateWindow("Test 2");

        init();
        Glut.glutDisplayFunc(myDisplay);
        Glut.glutMainLoop();
    }

Answer 1

Gl.glBegin(Gl.GL_POINT);

will cause a GL_INVALID_ENUM error, since GL_POINT is not a valid argument to glBegin. Check out the documentation one which draw modes are valid. You should also check for OpenGL errors at least at the end of a frame.