winforms - Strange rotation in C# graphics -

i using onpaint method in class class1 : panel.

protected override void onpaint(painteventargs e) {     base.onpaint(e);     graphics g = e.graphics;  } 

to rotate , draw rectangle using

matrix m = new matrix(); m.rotateat(90, rotationpoint); g.transform = m; g.fillrectangle(brushes.black, rectangle) 

the problem is, rotation isn't working want to.

red square rotation point , it's located in middle-top of rectangle. how set x, y , rotation point rotation work properly?

after rotating @ 90 degress should this

red pixel still @ same location.

rotation point not point, want rotate. point, around which graphics rotated. if draw rectangle on top of graphics , want rotate (rectangle) - should set rotation point center of graphics , rotate image 90 degrees.
here example, want:

base.onpaint(e);  var g = e.graphics; var width = g.visibleclipbounds.width; var height = g.visibleclipbounds.height; var rotationpoint = new pointf(width / 2, height / 2); ;  // draw center point g.fillrectangle(brushes.red, new rectanglef(rotationpoint.x - 5, rotationpoint.y - 5, 10, 10));  using (var path = new graphicspath()) {     var rectangle = new rectanglef((width - 10) / 2, 0, 10, 10);     var m = new matrix();     m.rotateat(90, rotationpoint);     path.addrectangle(rectangle);     path.transform(m);      // draw rotated point     g.fillpath(brushes.black, path); }