为防止点击窗体右上角的关闭按钮（X按钮）关闭窗体，我们可以覆盖WndProc过程，只要发现消息为WM_SYSCOMMAND且wparam参数为SC_CLOSE就不让继续传下去。

Delphi代码：

unit Unit1;interfaceuses  Winapi.Windows, Winapi.Messages, System.SysUtils, System.Variants, System.Classes, Vcl.Graphics,  Vcl.Controls, Vcl.Forms, Vcl.Dialogs;type  TForm1 = class(TForm)  private    {
     Private declarations }    procedure WndProc(var AMessage:TMessage);override;  public    {
     Public declarations }  end;var  Form1: TForm1;implementation{
    $R *.dfm}procedure TForm1.WndProc(var AMessage: TMessage);begin  if (AMessage.Msg=WM_SYSCOMMAND) and (AMessage.WParam=SC_CLOSE) then    Exit  else    inherited;end;end.

C#代码：

using System;using System.Collections.Generic;using System.ComponentModel;using System.Data;using System.Drawing;using System.Linq;using System.Text;using System.Windows.Forms;namespace WindowsFormsApplication7{    public partial class Form1 : Form    {        const int WM_SYSCOMMAND = 0x0112;        const int SC_CLOSE = 0xF060;        public Form1()        {            InitializeComponent();        }        protected override void WndProc(ref Message m)        {            if ((m.Msg == WM_SYSCOMMAND) && ((int)m.WParam == SC_CLOSE))                return;            base.WndProc(ref m);        }        private void Form1_Load(object sender, EventArgs e)        {        }    }}