How can I rotate a rectangle using a matrix and get the modified rectangle?

The System.Drawing.Rectanglestructure is always orthogonal and cannot be rotated. You can only rotate its corner points.

Here is an example of doing this using Matrix:

Matrix M = new Matrix();

// just a rectangle for testing..
Rectangle R = panel1.ClientRectangle;
R.Inflate(-33,-33);

// create an array of all corner points:
var p = new PointF[] {
    R.Location,
    new PointF(R.Right, R.Top),
    new PointF(R.Right, R.Bottom),
    new PointF(R.Left, R.Bottom) };

// rotate by 15° around the center point:
M.RotateAt(15, new PointF(R.X + R.Width / 2, R.Top + R.Height / 2));
M.TransformPoints(p);

// just a quick (and dirty!) test:
using (Graphics g = panel1.CreateGraphics())
{
    g.DrawRectangle(Pens.LightBlue, R);
    g.DrawPolygon(Pens.DarkGoldenrod, p );
}

The trick is to create an array that contains Pointor PointFcontains all the points you're interested in , here the four corners; you can Matrixthen transform those points based on various things you ask for, rotation around a point is one of them. Others include zoom , cut and pan .

The result is as expected:

If you need this functionality repeatedly, you need to create a function that converts a Rectangle to a Point[] and back.

Note that the latter is not actually possible as mentioned above, since it Rectangleis always orthogonal, i.e. cannot be rotated , so you have to look for the corners. Or switch to the class Rectfrom the namespace System.WindowsQuergo shows in its post .