Question

I am trying to create a function that will create a triangle, given a Rectangle structure. I have the following code:

public enum Direction {
    Up,
    Right,
    Down,
    Left
}

private void DrawTriangle(Graphics g, Rectangle r, Direction direction)
{
    if (direction == Direction.Up) {
        int half = r.Width / 2;

        g.DrawLine(Pens.Black, r.X, r.Y + r.Height, r.X + Width, r.Y + r.Height); // base
        g.DrawLine(Pens.Black, r.X, r.Y + r.Height, r.X + half, r.Y); // left side
        g.DrawLine(Pens.Black, r.X + r.Width, r.Y + r.Height, r.X + half, r.Y); // right side
    }
}

This works, as long as the direction is up. But I have two problems. First of all, is there a way to always draw it up, but simply rotate it 0, 90, 180 or 270 degrees respectively, to keep from having to use four if statements? Secondly, how can I fill the triangle in with a black color?

Answer 1

Graphics.Transform and Matrix.Rotate to solve rotation part. Graphics.FillPolygon for filling triangle.

Approximate not compiled code from samples to corresponding methods below:

// Create a matrix and rotate it 45 degrees.
Matrix myMatrix = new Matrix();
myMatrix.Rotate(45, MatrixOrder.Append);
graphics.Transform = myMatrix;
graphics.FillPolygon(new SolidBrush(Color.Blue), points);