用 PostMessage、SendNotifyMessage、SendMessageCallback 等異步函數(shù)發(fā)送系統(tǒng)消息時(shí)，參數(shù)里不可以使用指針，因?yàn)榘l(fā)送者并不等待消息的處理就返回，接受者還沒(méi)處理指針就已經(jīng)被釋放了。5、在 Windows 2000/XP 里，每個(gè)消息隊(duì)列最多只能存放 10,000 個(gè) Post 的消息，超過(guò)的還沒(méi)被處理的將不會(huì)被處理，直接丟掉。這個(gè)值可以改得更大：[HKEY_LOCAL_MACHINE/SOFTWARE/ Microsoft/Windows NT/CurrentVersion/Windows] USERPostMessageLimit，最小可以是 4000。PostMessage只負(fù)責(zé)將消息放到消息隊(duì)列中，不確定何時(shí)及是否處理SendMessage要等到受到消息處理的返回碼（DWord類(lèi)型）后才繼續(xù)PostMessage執(zhí)行后馬上返回SendMessage必須等到消息被處理后才會(huì)返回。下面通過(guò)一個(gè)小例子來(lái)說(shuō)明下這2個(gè)方法進(jìn)行參數(shù)傳遞的不同點(diǎn)：

//Win32 API 類(lèi)

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>
????????///?自定義的結(jié)構(gòu)
????????///?</summary>
????????public?struct?My_lParam
????????{
????????????public?int?i;
????????????public?string?s;
????????}
????????///?<summary>
????????///?使用COPYDATASTRUCT來(lái)傳遞字符串
????????///?</summary>
????????[StructLayout(LayoutKind.Sequential)]
????????public?struct?COPYDATASTRUCT
????????{
????????????public?IntPtr dwData;
????????????public?int?cbData;
????????????[MarshalAs(UnmanagedType.LPStr)]
????????????public?string?lpData;
????????}
????????//消息發(fā)送API
????????[DllImport("User32.dll",?EntryPoint =?"SendMessage")]
????????public?static?extern?int?SendMessage(
????????????IntPtr hWnd,????????// 信息發(fā)往的窗口的句柄
????????????int?Msg,????????????// 消息ID
????????????int?wParam,?????????// 參數(shù)1
????????????int?lParam??????????//參數(shù)2
????????);

????????
????????//消息發(fā)送API
????????[DllImport("User32.dll",?EntryPoint =?"SendMessage")]
????????public?static?extern?int?SendMessage(
????????????IntPtr hWnd,????????// 信息發(fā)往的窗口的句柄
????????????int?Msg,????????????// 消息ID
????????????int?wParam,?????????// 參數(shù)1
????????????ref?My_lParam lParam?//參數(shù)2
????????);
????????
????????//消息發(fā)送API
????????[DllImport("User32.dll",?EntryPoint =?"SendMessage")]
????????public?static?extern?int?SendMessage(
????????????IntPtr hWnd,????????// 信息發(fā)往的窗口的句柄
????????????int?Msg,????????????// 消息ID
????????????int?wParam,?????????// 參數(shù)1
????????????ref??COPYDATASTRUCT lParam??//參數(shù)2
????????);

????????//消息發(fā)送API
????????[DllImport("User32.dll",?EntryPoint =?"PostMessage")]
????????public?static?extern?int?PostMessage(
????????????IntPtr hWnd,????????// 信息發(fā)往的窗口的句柄
????????????int?Msg,????????????// 消息ID
????????????int?wParam,?????????// 參數(shù)1
????????????int?lParam????????????// 參數(shù)2
????????);
????????
????????
????????
????????//消息發(fā)送API
????????[DllImport("User32.dll",?EntryPoint =?"PostMessage")]
????????public?static?extern?int?PostMessage(
????????????IntPtr hWnd,????????// 信息發(fā)往的窗口的句柄
????????????int?Msg,????????????// 消息ID
????????????int?wParam,?????????// 參數(shù)1
????????????ref?My_lParam lParam?//參數(shù)2
????????);
????????
????????//異步消息發(fā)送API
????????[DllImport("User32.dll",?EntryPoint =?"PostMessage")]
????????public?static?extern?int?PostMessage(
????????????IntPtr hWnd,????????// 信息發(fā)往的窗口的句柄
????????????int?Msg,????????????// 消息ID
????????????int?wParam,?????????// 參數(shù)1
????????????ref??COPYDATASTRUCT lParam??// 參數(shù)2
????????);

????}
}

//主窗體，發(fā)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);//傳遞2個(gè)整型參數(shù)成功
????????????????}
????????????????if(DateTime.Now.Second?%?3?==?0)
????????????????{
????????????????????Win32API.SendMessage(hwndTest,?0x61,?5,?ref?lp);//傳遞整型參數(shù)和結(jié)構(gòu)類(lèi)型成功，這個(gè)方法加以改變后可以傳遞對(duì)象
????????????????}
????????????????if(DateTime.Now.Second?%?5?==?0)
????????????????{
????????????????????Win32API.SendMessage(hwndTest,?0x62,?5,?ref?cds);//傳遞整型參數(shù)和不定長(zhǎng)的字符串成功
????????????????}
????????????????if(DateTime.Now.Second?%?7?==?0)
????????????????{
????????????????????Win32API.PostMessage(hwndTest,?0x63,?5,?6);//傳遞2個(gè)整型參數(shù)成功
????????????????}
????????????????if(DateTime.Now.Second?%?9?==?0)
????????????????{
????????????????????Win32API.PostMessage(hwndTest,?0x64,?3,?ref?lp);//傳遞整型參數(shù)成功，但是傳遞參數(shù)lp失敗，3可以傳遞成功。
????????????????}
????????????????if(DateTime.Now.Second?%?11?==?0)
????????????????{
????????????????????Win32API.PostMessage(hwndTest,?0x65,?3,?ref?cds);//傳遞整型參數(shù)成功，傳遞參數(shù)cds失敗，3可以傳遞成功。
????????????????}
????????????}
???????????
????????????
????????}
????}
}

//子窗體接收消息以及參數(shù)

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;
????????????
????????}

????????

????????///重寫(xiě)窗體的消息處理函數(shù)DefWndProc，從中加入自己定義消息的檢測(cè)的處理入口
????????protected?override?void?DefWndProc(ref?Message m)
????????{
????????????switch?(m.Msg)
????????????{
????????????????????//接收自定義消息MYMESSAGE，并顯示其參數(shù)
????????????????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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