From1.Location = new Point(x, y);

------解决方案--------------------
C# code
[DllImport("user32.dll",EntryPoint="MoveWindow")]
public static extern int MoveWindow(int hwnd, int x, int y, int nWidth, int nHeight, int bRepaint)

------解决方案--------------------
C# code
using System;
using System.Drawing;
using System.Windows.Forms;
using System.Runtime.InteropServices;

class Form1 : Form
{
  Random rand = new Random();
  
  protected override void OnPaint(PaintEventArgs e)
  {
    e.Graphics.DrawString
    (
      "单击窗体客户区，\r\n则窗体会随机移动\r\n并改变大小，\r\n很有趣吧！",
      new Font("Arial", 16),
      new SolidBrush(Color.Blue),
      0,
      0
    );
    base.OnPaint(e);
  }
  
  [DllImport("user32.dll",EntryPoint="MoveWindow")]
  public static extern int MoveWindow(IntPtr hwnd, int x, int y, int nWidth, int nHeight, bool bRepaint);

  // 这是使用 API 的版本
  protected override void OnClick(EventArgs e)
  {
    int x       = rand.Next(800);
    int y       = rand.Next(600);
    int nWidth  = rand.Next(50, 500);
    int nHeight = rand.Next(50, 500);
    MoveWindow(Handle, x, y, nWidth, nHeight, true);
    base.OnClick(e);
  }

  /*
  // 这是不使用 API 的版本
  protected override void OnClick(EventArgs e)
  {
    Left   = rand.Next(800);
    Top    = rand.Next(600);
    Width  = rand.Next(50, 500);
    Height = rand.Next(50, 500);
    base.OnClick(e);
  }
  */
  
  static void Main()
  {
    Application.Run(new Form1());
  }
}