private void pictureBox1_Paint(object sender, PaintEventArgs e)
        {
            e.Graphics.FillRectangle(Brushes.Red, 0, 0, 100, 100);

        }

------解决方案--------------------
探讨

C# code


        private void pictureBox1_Paint(object sender, PaintEventArgs e)
        {
            e.Graphics.FillRectangle(Brushes.Red, 0, 0, 100, 100);

        }