I've worked out most of the code and have several game classes. The one bit I'm stuck on at the moment, it how to draw the actual Connect 4 grid. Can anyone tell me what's wrong with this for loop? I get no errors but the grid doesn't appear. I'm using C#.

private void Drawgrid() {

        Brush b = Brushes.Black;
        Pen p = Pens.Black;

        for (int xCoor = XStart, col = 0; xCoor < XStart + ColMax * DiscSpace; xCoor += DiscSpace, col++)

            // x coordinate beginning; while the x coordinate is smaller than the max column size, times it by
            // the space between each disc and then add the x coord to the disc space in order to create a new circle.

        for (int yCoor = YStart, row = RowMax - 1; yCoor < YStart + RowMax * DiscScale; yCoor += DiscScale, row--)
            {


                switch (Grid.State[row, col])
                {
                    case GameGrid.Gridvalues.Red:
                        b = Brushes.Red;
                        break;

                    case GameGrid.Gridvalues.Yellow:
                        b = Brushes.Yellow;
                        break;

                    case GameGrid.Gridvalues.None:
                        b = Brushes.Aqua;
                        break;

                }
                MainDisplay.DrawEllipse(p, xCoor, yCoor, 50, 50);
                MainDisplay.FillEllipse(b, xCoor, yCoor, 50, 50);
            }
        Invalidate();



    }

Thanks.