Bitmap bmp;

        private void menuStrip1_ItemClicked(object sender, ToolStripItemClickedEventArgs e)
        {
            openFileDialog1.Filter = "*.gif|*.gif|*.jpg|*.jpg|*.bmp|*.bmp";
            if (openFileDialog1.ShowDialog()==DialogResult.OK)
            {
                bmp = new Bitmap(openFileDialog1.FileName);
                this.Invalidate();
            }
        }

        private void button1_Paint(object sender, PaintEventArgs e)
        {
            if (bmp != null)
            {
                Graphics grap = e.Graphics;
                TextureBrush theBrush = new TextureBrush(bmp);
                grap.FillRectangle(theBrush, this.ClientRectangle);
            }
        }

運用Drawing的Api讓button呈現Image的效果