Hit testing problem

Question

I need to write a program which can draw rectangle by mouse. User can draw a rectangle by click left mouse button and drag mouse, when user release left mouse button, rectangle will be drawn. Now I can draw rectangle, but I want to check when I move mouse, program can show me the mouse is inside a rectangle or not. I use an RectangleArray which inherits from CollectionBase to store all drawn rectangle. In mose move method, I loop through this array and use Contains method of Rectangle class to check the mouse inside or not. But I don't understand while I only can check the position of mouse if it is inside the first rectangle I drawn (label4 does not change value). But if I show a message box, label4 can change its value. private void picImage_MouseMove(object sender, MouseEventArgs e) { Point mousePoint = new Point(e.X, e.Y); foreach (Rectangle rect in rects) { if (rect .Contains(mousePoint)) { label4.Text = "In rect"; //MessageBox.Show(mouseIsInShelf.ToString()); break; } else { label4.Text = "Not in rect"; } } } Can anybody help me? Thanks a lot!