WinForm:API

一、WndProc: 

主要用在拦截并处理系统消息和自定义消息

比如:
windows程序会产生很多消息，比如你单击鼠标，移动窗口都会产生消息。这个函数就是默认的消息处理函数。你可以重载这个函数来制定自己的消息处理流程.

在Winform程序中，可以重写WndProc函数，来捕捉所有发生的窗口消息。

这样，我们就可以"篡改"传入的消息，而人为的让窗口改变行为。

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;
using System.Runtime.InteropServices;

namespace ControlTest
{
    public partial class Form1 : Form
    {
        public Form1()
        {
            InitializeComponent();
        }

        private Demo demo = null;
        private void Form1_Load(object sender, EventArgs e)
        {
            //demo = new Demo(this.Handle.ToInt32());
        }

        private void button1_Click(object sender, EventArgs e)
        {
            demo = new Demo(this.Handle.ToInt32());
            demo.Test();
        }

        protected override void WndProc(ref Message m)
        {
            if (m.Msg == Demo.MY_MSG_BEGIN)
            {
                MessageBox.Show("类Demo for循环开始.");
            }
            else if (m.Msg == Demo.MY_MSG_END)
            {
                MessageBox.Show("类Demo for循环结束.");
            }

            base.WndProc(ref m);
        }
    }

    public class Demo
    {
        private int m_hWnd = 0;

        public Demo(int hWnd)
        {
            m_hWnd = hWnd;
        }

        private const int WM_USER = 0x0400;
        public static int MY_MSG_BEGIN = WM_USER + 100;
        public static int MY_MSG_END = WM_USER + 101;

        [DllImport("User32.DLL")]
        public static extern int SendMessage(int hWnd, int Msg, int wParam, int lParam);

        public void Test()
        {
            SendMessage(m_hWnd, MY_MSG_BEGIN, 0, 0);
            for (int i = 0; i < 100000; i++)
            {
                Application.DoEvents();
            }
            SendMessage(m_hWnd, MY_MSG_END, 0, 0);
        }
    }
   
}

二、SendMessage：

该函数将指定的消息发送到一个或多个窗口。此函数为指定的窗口调用窗口程序，直到窗口程序处理完消息再返回。而函数PostMessage不同，将一个消息寄送到一个线程的消息队列后立即返回。

函数原型：LRESULT SendMessage（HWND hWnd，UINT Msg，WPARAM wParam，LPARAM IParam）；

    参数：

    hWnd：其窗口程序将接收消息的窗口的句柄。如果此参数为HWND_BROADCAST，则消息将被发送到系统中所有顶层窗口，包括无效或不可见的非自身拥有的窗口、被覆盖的窗口和弹出式窗口，但消息不被发送到子窗口。

    Msg：指定被发送的消息。

    wParam：指定附加的消息指定信息。

    IParam：指定附加的消息指定信息。

    返回值：返回值指定消息处理的结果，依赖于所发送的消息。

    备注：需要用HWND_BROADCAST通信的应用程序应当使用函数RegisterWindowMessage来为应用程序间的通信取得一个唯一的消息。

    如果指定的窗口是由调用线程创建的，则窗口程序立即作为子程序调用。如果指定的窗口是由不同线程创建的，则系统切换到该线程并调用恰当的窗口程序。线程间的消息只有在线程执行消息检索代码时才被处理。发送线程被阻塞直到接收线程处理完消息为止。

 SendMessage是一个在user32.dll中声明的API函数，在C#中导入如下：

using System.Runtime.InteropServices;
[DllImport("user32.dll", EntryPoint="SendMessageA")]
public static extern int SendMessage (IntPtr hwnd, int wMsg, IntPtr wParam, IntPtr lParam);

本文描述其参数 lParam 的用法，主要是数据类型之间的转化。

● 一种最简单的处理方式是声明多个SendMessage函数(overload)，用所需的数据类型直接替换IntPtr。例如：

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//声明:
[DllImport("user32.dll", EntryPoint="SendMessageA")]
private static extern int SendMessage (IntPtr hwnd, int wMsg, IntPtr wParam,  string lParam);
[DllImport("user32.dll", EntryPoint="SendMessageA")]
private static extern int SendMessage (IntPtr hwnd, int wMsg, IntPtr wParam,  ref Rectangle lParam);
//调用:
string s = "hello, floodzhu";
SendMessage(this.textBox1.Handle, WM_SETTEXT, IntPtr.Zero, s);

Rectangle rect = new Rectangle();
SendMessage(this.richTextBox1.Handle, EM_GETRECT, (IntPtr)0, ref rect);
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● 对要求返回字符串的类型（out string）可以用 StringBuilder 代替，此时不需要 out/ref。例如：

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[DllImport("user32.dll", EntryPoint="SendMessageA")]
private static extern int SendMessage (IntPtr hwnd, int wMsg, int wParam, StringBuilder lParam);
private void button1_Click(object sender, System.EventArgs e)
{
    const int buffer_size = 1024;
    StringBuilder buffer = new StringBuilder(buffer_size);
    SendMessage(this.textBox1.Handle, WM_GETTEXT, buffer_size, buffer);
    //MessageBox.Show(buffer.ToString());
}
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● 如果想用 InPtr 类型统一处理的话，可以借助于 Marshal 或者 GCHandle 的相关方法。例如：

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[DllImport("user32.dll", EntryPoint="SendMessageA")]
private static extern int SendMessage (IntPtr hwnd, int wMsg, IntPtr wParam, IntPtr lParam);

private void button2_Click(object sender, System.EventArgs e)
{
    Rectangle rect = new Rectangle();
    IntPtr buffer = Marshal.AllocHGlobal(Marshal.SizeOf(typeof(Rectangle)));
    Marshal.StructureToPtr(rect, buffer ,true);

    SendMessage(this.richTextBox1.Handle, EM_GETRECT, (IntPtr)0, buffer);

    rect = (Rectangle)Marshal.PtrToStructure(buffer, typeof(Rectangle));

    Marshal.FreeHGlobal(buffer);
}
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或者

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private void button2_Click(object sender, System.EventArgs e)
{
    Rectangle rect = new Rectangle();
    GCHandle gch = GCHandle.Alloc(rect);

    SendMessage(this.richTextBox1.Handle, EM_GETRECT, (IntPtr)0, (IntPtr)gch);
    rect = (Rectangle)Marshal.PtrToStructure((IntPtr)gch, typeof(Rectangle));

    gch.Free();
}
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● 模拟按钮点击。第三个参数是可选参数，有时需要有时不需要，比如该例中就不需要。

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const int BM_CLICK = 0xF5;
IntPtr maindHwnd = FindWindow(null, "QQ用户登录"); //获得QQ登陆框的句柄
if (maindHwnd != IntPtr.Zero)
{
    IntPtr childHwnd = FindWindowEx(maindHwnd, IntPtr.Zero, null, "登录");   //获得按钮的句柄
    if (childHwnd != IntPtr.Zero)
    {
        SendMessage(childHwnd, BM_CLICK, 0, 0);     //发送点击按钮的消息
    }
    else
    {
        MessageBox.Show("没有找到子窗口");
    }
}
else
{
    MessageBox.Show("没有找到窗口");
}
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 三、PostMessage:

用 PostMessage、SendNotifyMessage、SendMessageCallback 等异步函数发送系统消息时，参数里不可以使用指针，因为发送者并不等待消息的处理就返回，接受者还没处理指针就已经被释放了。

PostMessage只负责将消息放到消息队列中，不确定何时及是否处理 SendMessage要等到受到消息处理的返回码（DWord类型）后才继续 PostMessage执行后马上返回 SendMessage必须等到消息被处理后才会返回。 下面通过一个小例子来说明下这2个方法进行参数传递的不同点： 

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//Win32 API 类


using System;
using System.Runtime.InteropServices;

namespace TestHwnd
 {
     public class Win32API
     {        
         [DllImport("User32.dll", EntryPoint = "FindWindow")]
         public static extern IntPtr FindWindow(string lpClassName, string lpWindowName);

         [DllImport("User32.dll", EntryPoint = "FindWindowEx")]
         public static extern IntPtr FindWindowEx(IntPtr hwndParent, IntPtr hwndChildAfter, string lpClassName, string lpWindowName);

         /// <summary>
         /// 自定义的结构
        /// </summary>
         public struct My_lParam
         {
             public int i;
             public string s;
         }
         /// <summary>
         /// 使用COPYDATASTRUCT来传递字符串
        /// </summary>
         [StructLayout(LayoutKind.Sequential)]
         public struct COPYDATASTRUCT
         {
             public IntPtr dwData;
             public int cbData;
             [MarshalAs(UnmanagedType.LPStr)]
             public string lpData;
         }
         //消息发送API
         [DllImport("User32.dll", EntryPoint = "SendMessage")]
         public static extern int SendMessage(
             IntPtr hWnd,        // 信息发往的窗口的句柄
            int Msg,            // 消息ID
             int wParam,         // 参数1
             int lParam          //参数2
         );

         
         //消息发送API
         [DllImport("User32.dll", EntryPoint = "SendMessage")]
         public static extern int SendMessage(
             IntPtr hWnd,        // 信息发往的窗口的句柄
            int Msg,            // 消息ID
             int wParam,         // 参数1
             ref My_lParam lParam //参数2
         );
         
         //消息发送API
         [DllImport("User32.dll", EntryPoint = "SendMessage")]
         public static extern int SendMessage(
             IntPtr hWnd,        // 信息发往的窗口的句柄
            int Msg,            // 消息ID
             int wParam,         // 参数1
             ref  COPYDATASTRUCT lParam  //参数2
         );

         //消息发送API
         [DllImport("User32.dll", EntryPoint = "PostMessage")]
         public static extern int PostMessage(
             IntPtr hWnd,        // 信息发往的窗口的句柄
            int Msg,            // 消息ID
             int wParam,         // 参数1
             int lParam            // 参数2
         );
         
         
         
         //消息发送API
         [DllImport("User32.dll", EntryPoint = "PostMessage")]
         public static extern int PostMessage(
             IntPtr hWnd,        // 信息发往的窗口的句柄
            int Msg,            // 消息ID
             int wParam,         // 参数1
             ref My_lParam lParam //参数2
         );
         
         //异步消息发送API
         [DllImport("User32.dll", EntryPoint = "PostMessage")]
         public static extern int PostMessage(
             IntPtr hWnd,        // 信息发往的窗口的句柄
            int Msg,            // 消息ID
             int wParam,         // 参数1
             ref  COPYDATASTRUCT lParam  // 参数2
         );

     }
 }

//主窗体，发送消息


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;
using System.Runtime.InteropServices;

namespace TestHwnd
 {
     public partial class Main : Form
     {

         public IntPtr hwndTest;
         public int IwndTest;
         public IntPtr hwndfrmTest;
         

         public Main()
         {
             InitializeComponent();
         }

         private void button1_Click(object sender, EventArgs e)
         {
             Test test = new Test();
             test.Show(this);
         }

         private void timer1_Tick(object sender, EventArgs e)
         {
             string strTest = "25425";
             Win32API.COPYDATASTRUCT cds;
             cds.dwData = (IntPtr)100;
             cds.lpData = strTest;
             byte[] sarr = System.Text.Encoding.UTF8.GetBytes(strTest);
             int len = sarr.Length;
             cds.cbData = len + 1;
             
             Win32API.My_lParam lp=new Win32API.My_lParam();
             lp.i=3;
             lp.s="test";
             
             if(hwndTest!=(IntPtr)0)
             {
                 if (DateTime.Now.Second % 2 == 0)
                 {
                     Win32API.SendMessage(hwndTest, 0x60, 1, 3);//传递2个整型参数成功
                }
                 if(DateTime.Now.Second % 3 == 0)
                 {
                     Win32API.SendMessage(hwndTest, 0x61, 5, ref lp);//传递整型参数和结构类型成功，这个方法加以改变后可以传递对象
                }
                 if(DateTime.Now.Second % 5 == 0)
                 {
                     Win32API.SendMessage(hwndTest, 0x62, 5, ref cds);//传递整型参数和不定长的字符串成功
                }
                 if(DateTime.Now.Second % 7 == 0)
                 {
                     Win32API.PostMessage(hwndTest, 0x63, 5, 6);//传递2个整型参数成功
                }
                 if(DateTime.Now.Second % 9 == 0)
                 {
                     Win32API.PostMessage(hwndTest, 0x64, 3, ref lp);//传递整型参数成功，但是传递参数lp失败，3可以传递成功。
                }
                 if(DateTime.Now.Second % 11 == 0)
                 {
                     Win32API.PostMessage(hwndTest, 0x65, 3, ref cds);//传递整型参数成功，传递参数cds失败，3可以传递成功。
                }
             }                        
         }
     }
 }




//子窗体接收消息以及参数
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;
using System.Runtime.InteropServices;

namespace TestHwnd
 {
     public partial class Test : Form
     {
         Main main;
         public Test()
         {
             InitializeComponent();
         }

         private void Test_Load(object sender, EventArgs e)
         {
             main = this.Owner as Main;
             main.hwndTest = this.Handle;
             
         }

         

         ///重写窗体的消息处理函数DefWndProc，从中加入自己定义消息的检测的处理入口
        protected override void DefWndProc(ref Message m)
         {
             switch (m.Msg)
             {
                     //接收自定义消息MYMESSAGE，并显示其参数
                case 0x60:
                     {
                         label1.Text = DateTime.Now.ToString() + "-" + m.WParam.ToInt32().ToString() + "-" + m.LParam.ToInt32().ToString();
                     }
                     break;
                 case 0x61:
                     {
                         Win32API.My_lParam ml = new Win32API.My_lParam();
                         Type t = ml.GetType();
                         ml = (Win32API.My_lParam)m.GetLParam(t);
                         label2.Text = DateTime.Now.ToString() + "-" + m.WParam.ToInt32().ToString() + "-" + ml.i.ToString()+":"+ml.s;
                     }
                     break;
                     case 0x62:
                     {
                         Win32API.COPYDATASTRUCT mystr = new Win32API.COPYDATASTRUCT();
                         Type mytype = mystr.GetType();
                         mystr = (Win32API.COPYDATASTRUCT)m.GetLParam(mytype);
                         string str2 = mystr.lpData;
                         label3.Text = DateTime.Now.ToString() + "-" + m.WParam.ToInt32().ToString() + "-" + str2;
                     }
                     break;
                     case 0x63:
                     {
                         label4.Text = DateTime.Now.ToString() + "-" + m.WParam.ToInt32().ToString() + "-" + m.LParam.ToInt32().ToString();
                     }
                     break;
                     case 0x64:
                     {
                         Win32API.My_lParam ml = new Win32API.My_lParam();
                         Type t = ml.GetType();
                         ml = (Win32API.My_lParam)m.GetLParam(t);
                         label5.Text = DateTime.Now.ToString() + "-" + m.WParam.ToInt32().ToString() + "-" + ml.i.ToString()+":"+ml.s;
                     }
                     break;
                     case 0x65:
                     {
                         Win32API.COPYDATASTRUCT mystr = new Win32API.COPYDATASTRUCT();
                         Type mytype = mystr.GetType();
                         mystr = (Win32API.COPYDATASTRUCT)m.GetLParam(mytype);
                         string str2 = mystr.lpData;
                         label6.Text = DateTime.Now.ToString() + "-" + m.WParam.ToInt32().ToString() + "-" + str2;
                     }
                     break;
                 default:
                     base.DefWndProc(ref m);
                     break;
             }
         }

         
         private void button1_Click(object sender, EventArgs e)
         {
             main.hwndTest = (IntPtr) (0);
             this.Close();
         }
     }    
 }
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原文地址：https://www.cnblogs.com/qi123/p/8398353.html