以下这段C#代码实现的功能是在屏幕上画图的效果！具体代码如下：
代码如下:
//DllImport所在的名字空间
using System.Runtime.InteropServices;
[DllImport("User32.dll")]
public extern static System.IntPtr GetDC(System.IntPtr hWnd);
private void button19_Click(object sender, EventArgs e)
{
System.IntPtr DesktopHandle = GetDC(System.IntPtr.Zero);
Graphics g = Graphics.FromHdc(DesktopHandle);
g.DrawRectangle(new Pen(Color.Red),new Rectangle(10,10,100,100));
}