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在C#中SendMessage和PostMessage的参数通报详解【C#.Net教程】,C#，SendMessage，PostMessage

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在C#中能够运用Window API供应的SendMessage和PostMessage来通报参数。二者的区分简朴引见下：返回值的差别，我们先看一下 MSDN 里的声明： 

LRESULT SendMessage(

HWND hWnd,

UINT Msg,


WPARAM wParam,

LPARAM lParam

);


BOOL PostMessage(

HWND hWnd,

UINT Msg,


WPARAM wParam,

LPARAM lParam

);


个中 4 个参数的意义是一样的，返回值范例差别（实在从数据上看他们一样是一个 32 位的数，只是意义不一样），LRESULT 示意的是音讯被处置惩罚后的返回值，BOOL 示意的是音讯是不是是 Post 胜利。


2、PostMessage 是异步的，SendMessage 是同步的。
PostMessage 只把音讯放入行列，不论音讯是不是被处置惩罚就返回，音讯能够不被处置惩罚；而 SendMessage 守候音讯被处置惩罚完了以后才返回，假如音讯不被处置惩罚，发送音讯的线程将一向被壅塞。


3、假如在统一个线程内，SendMessage 发送音讯时，由 USER32.DLL
模块挪用目的窗口的音讯处置惩罚顺序，并将效果返回。SendMessage 在统一线程中发送音讯并不入线程音讯行列。PostMessage
发送音讯时，音讯要先放入线程的音讯行列，然后经由过程音讯轮回分派到目的窗口（DispatchMessage）。


假如在差别线程内，SendMessage 发送音讯到目的窗口所属线程的音讯行列，然后发送音讯的线程在 USER32.DLL
模块内看管和守候音讯处置惩罚，直到目的窗口处置惩罚完返回。SendMessage 在返回前还做了许多事情，比方，相应别的线程向它
SendMessage。Post 到别的线程时，最好用 PostThreadMessage 替代
PostMessage，PostMessage 的 hWnd 参数能够是 NULL，等效于 PostThreadMessage +
GetCurrentThreadId。Post WM_QUIT 时，应运用 PostQuitMessage 替代。

4、体系只整编（marshal）体系音讯（0 到 WM_USER 之间的音讯），发送用户音讯（WM_USER 以上）到别的历程时，须要本身做整编。

用 PostMessage、SendNotifyMessage、SendMessageCallback 等异步函数发送体系音讯时，参数里不能够运用指针，由于发送者并不守候音讯的处置惩罚就返回，接受者还没处置惩罚指针就已被释放了。 5、在 Windows 2000/XP 里，每一个音讯行列最多只能寄存 10,000 个 Post 的音讯，凌驾的还没被处置惩罚的将不会被处置惩罚，直接丢掉。这个值能够改得更大：[HKEY_LOCAL_MACHINE/SOFTWARE/ Microsoft/Windows NT/CurrentVersion/Windows] USERPostMessageLimit，最小能够是 4000。 PostMessage只担任将音讯放到音讯行列中，不确定什么时候及是不是处置惩罚 SendMessage要比及遭到音讯处置惩罚的返回码（DWord范例）后才继承 PostMessage实行后立时返回 SendMessage必需比及音讯被处置惩罚后才会返回。 下面经由过程一个小例子来申明下这2个要领举行参数通报的差别点：
//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>
        /// 自定义的构造
        /// </summary>
        public struct My_lParam
        {
            public int i;
            public string s;
        }
        /// <summary>
        /// 运用COPYDATASTRUCT来通报字符串
        /// </summary>
        [StructLayout(LayoutKind.Sequential)]
        public struct COPYDATASTRUCT
        {
            public IntPtr dwData;
            public int cbData;
            [MarshalAs(UnmanagedType.LPStr)]
            public string lpData;
        }
        //音讯发送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,            // 音讯ID
            int wParam,         // 参数1
            int lParam          //参数2
        );


        //音讯发送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,            // 音讯ID
            int wParam,         // 参数1
            ref My_lParam lParam //参数2
        );
        
        //音讯发送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,            // 音讯ID
            int wParam,         // 参数1
            ref  COPYDATASTRUCT lParam  //参数2
        );


        //音讯发送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,            // 音讯ID
            int wParam,         // 参数1
            int lParam            // 参数2
        );
        
        
        
        //音讯发送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,            // 音讯ID
            int wParam,         // 参数1
            ref My_lParam lParam //参数2
        );
        
        //异步音讯发送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,            // 音讯ID
            int wParam,         // 参数1
            ref  COPYDATASTRUCT lParam  // 参数2
        );


    }
}


//主窗体，发送音讯

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);//通报2个整型参数胜利
                }
                if(DateTime.Now.Second % 3 == 0)
                {
                    Win32API.SendMessage(hwndTest, 0x61, 5, ref lp);//通报整型参数和构造范例胜利，这个要领加以转变后能够通报对象
                }
                if(DateTime.Now.Second % 5 == 0)
                {
                    Win32API.SendMessage(hwndTest, 0x62, 5, ref cds);//通报整型参数和不定长的字符串胜利
                }
                if(DateTime.Now.Second % 7 == 0)
                {
                    Win32API.PostMessage(hwndTest, 0x63, 5, 6);//通报2个整型参数胜利
                }
                if(DateTime.Now.Second % 9 == 0)
                {
                    Win32API.PostMessage(hwndTest, 0x64, 3, ref lp);//通报整型参数胜利，然则通报参数lp失利，3能够通报胜利。
                }
                if(DateTime.Now.Second % 11 == 0)
                {
                    Win32API.PostMessage(hwndTest, 0x65, 3, ref cds);//通报整型参数胜利，通报参数cds失利，3能够通报胜利。
                }
            }
            
            
        }
    }
}


//子窗体吸收音讯以及参数

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;
            
        }

        ///重写窗体的音讯处置惩罚函数DefWndProc，从中到场本身定义音讯的检测的处置惩罚进口
        protected override void DefWndProc(ref Message m)
        {
            switch (m.Msg)
            {
                    //吸收自定义音讯MYMESSAGE，并显现其参数
                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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