C#如何使用API函数

下面是一个简单的例子，调用API实现了禁用关闭按钮的功能

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Text;
using System.Windows.Forms;
using System.Runtime.InteropServices;

namespace winFormTest
{
public partial class Form2 : Form
{
[DllImport("USER32.DLL")]
public static extern int GetSystemMenu(int hwnd, int bRevert);
[DllImport("USER32.DLL")]
public static extern int RemoveMenu(int hMenu, int nPosition, int wFlags);

const int MF_REMOVE = 0x1000;

const int SC_RESTORE = 0xF120; //还原
const int SC_MOVE = 0xF010; //移动
const int SC_SIZE = 0xF000; //大小
const int SC_MINIMIZE = 0xF020; //最小化
const int SC_MAXIMIZE = 0xF030; //最大化
const int SC_CLOSE = 0xF060; //关闭

public Form2()