private void button1_Click(object sender, EventArgs e)
{
AcadApplication acadApp = AcadApp.AcadApplication as AcadApplication;
IntPtr AcadHwnd = (IntPtr)acadApp.HWND;//获取AutoCAD应用程序的窗口句柄
Graphics vGraphics = Graphics.FromHwnd(AcadHwnd);
vGraphics.DrawLine(Pens.Red, 0, 0, 100, 100);
}