怎样获取CAD绘图区域左上角的屏幕坐标

using System;
using System.Runtime.InteropServices;
using System.Windows.Forms;
using Application = Autodesk.AutoCAD.ApplicationServices.Core.Application;
namespace 取得CAD绘图区域屏幕坐标
{
public partial class Form1 : Form
{
public Form1()
{
InitializeComponent();
}
[DllImport("user32.DLL", EntryPoint = "GetTopWindow", SetLastError = true, CharSet = CharSet.Unicode,
ExactSpelling = true, CallingConvention = CallingConvention.StdCall)]
public static extern IntPtr GetTopWindow(IntPtr hWnd);
[DllImport("user32.dll", SetLastError = true, CharSet = CharSet.Auto)]
public static extern IntPtr GetWindow(IntPtr hWnd, UInt32 uCmd);
[DllImport("user32.dll")]
[return: MarshalAs(UnmanagedType.Bool)]
static extern bool GetWindowRect(IntPtr hWnd, ref Rect lpRect);
[StructLayout(LayoutKind.Sequential)]
public struct Rect
{
public int Left; //最左坐标
public int Top; //最上坐标
public int Right; //最右坐标
public int Bottom; //最下坐标
}
private void button1_Click(object sender, EventArgs e)
{
Rect rect = new Rect();
IntPtr intPtr1 = GetTopWindow(Application.DocumentManager.MdiActiveDocument.Window.Handle);
textBox1.Text = intPtr1.ToString();
IntPtr intPtr2 = GetWindow(intPtr1, 2);
GetWindowRect(intPtr2, ref rect);
textBox2.Text = rect.Left.ToString();
textBox3.Text = rect.Top.ToString();
textBox4.Text = (rect.Right - rect.Left).ToString();
textBox5.Text = (rect.Bottom - rect.Top).ToString();
}
}
}

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