.NET中使用API绘图 
using System;
using System.Drawing;
using System.Collections;
using System.ComponentModel;
using System.Windows.Forms;
using System.Data;
using System.Runtime.InteropServices;

namespace API
{
    
/// <summary>
    
/// Form1 的摘要说明。
    
/// </summary>

    public class Form1 : System.Windows.Forms.Form
    
{
        
/// <summary>
        
/// 必需的设计器变量。
        
/// </summary>

        private System.ComponentModel.Container components = null;

        
public Form1()
        
{
            
//
            
// Windows 窗体设计器支持所必需的
            
//
            InitializeComponent();

            
//
            
// TODO: 在 InitializeComponent 调用后添加任何构造函数代码
            
//
        }


        
/// <summary>
        
/// 清理所有正在使用的资源。
        
/// </summary>

        protected override void Dispose( bool disposing )
        
{
            
if( disposing )
            
{
                
if (components != null
                
{
                    components.Dispose();
                }

            }

            
base.Dispose( disposing );
        }


        
Windows Form Designer generated code

        
/// <summary>
        
/// 应用程序的主入口点。
        
/// </summary>

        [STAThread]
        
static void Main() 
        
{
            Application.Run(
new Form1());
        }


        [StructLayout(LayoutKind.Sequential)]
        
public struct LPPOINT
        
{
            
public long x;
            
public long y;
        }


        [DllImport(
"gdi32.dll")] 
        
private static extern bool SetROP2(IntPtr hdc,int nDrawMode);

        [DllImport(
"gdi32.dll")]
        
private static extern bool Rectangle
            (IntPtr hdc,
int X1,  int Y1,int X2, int Y2);

        [DllImport(
"gdi32.dll")]
        
private static extern long CreatePen(int nPenStyle,
            
int nWidth, long crColor);

        [DllImport(
"gdi32.dll")]
        
private static extern long SelectObject(IntPtr hdc,
            
long hObject);

        [DllImport(
"gdi32.dll")]
        
private static extern long DeleteObject(long hObject);

        
//绘矩形
        public void Draw(Graphics g, long aColor)
        
{
            IntPtr hdc;
            hdc 
=g.GetHdc();
            SetROP2(hdc, 
10);
            
long p,oldP;
            p 
= CreatePen(01, aColor);
            oldP 
= SelectObject(hdc, p);
            Rectangle(hdc, 
20150170250);
            SelectObject(hdc, oldP);
            DeleteObject(p);
            g.ReleaseHdc(hdc);
        }


        
protected override void OnPaint(PaintEventArgs e)
        
{
            Graphics g 
= e.Graphics;
            g.FillRectangle(Brushes.White, 
this.ClientRectangle);
            
//用GDI+函数绘一个兰色矩形
            g.DrawRectangle(Pens.Blue, 2020150100);
            
//用API函数绘一个红色矩形
            Draw(g,255);
        }

    }

}