[C#/win32 API] SendMessage() 與 PostMessage()

網路上比較少SendMessage()跟PostMessage資料

先給SendMessage範例

SendMessage會等到接收端check後才會繼續執行,而PostMessage則是丟入訊息queue,繼續做。

以下範例都要先加入 using System.Runtime.InteropServices;

SendMessage A端(控制端):

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 TestA
{
    public partial class Form1 : Form
    {
        [DllImport("user32.dll")]
        private static extern int SendMessage(IntPtr hwnd, uint wMsg, int wParam, IntPtr lParam);

        [DllImport("user32.dll", SetLastError = true, CharSet = CharSet.Auto)]
        static extern uint RegisterWindowMessage(string lpString);
        uint MSG_SHOW = RegisterWindowMessage("Show Message");

        [DllImport("user32.dll")]
        static extern IntPtr FindWindow(string lpClassName, string lpWindowName);
     

        public Form1()
        {
            InitializeComponent();
        }

        private void button1_Click_1(object sender, EventArgs e)
        {
            IntPtr form_name = FindWindow(null, "要控制的視窗元件名稱(text,不是name)");//找B的IntPtr 用來代表指標或控制代碼

            if (form_name != IntPtr.Zero)
            {
                try
                {
                    int iNum = 9527;
                    SendMessage(form_name, MSG_SHOW, iNum, IntPtr.Zero);
                }
                catch (Exception)
                {
                }
            }
        }
    }
}

SendMessage B端(接收端):

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 TestB

{

    public partial class TestB_1 : Form

    {

        [DllImport("user32.dll", SetLastError = true, CharSet = CharSet.Auto)]

        static extern uint RegisterWindowMessage(string lpString);

        uint MSG_SHOW = RegisterWindowMessage("Show Message");

        public TestB_1()

        {

            InitializeComponent();

        }

        protected override void WndProc(ref Message m)

        {

            if (m.Msg == MSG_SHOW)

            {

                label1.Text = (string)m.WParam.ToString();

            }

            base.WndProc(ref m);

        }

    }

}

PostMessage A端(呼叫端):

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

        [DllImport("user32.dll", EntryPoint = "FindWindow", CharSet = CharSet.Auto)]
        private extern static IntPtr FindWindow(string lpClassName, string lpWindowName);
 
        [DllImport("user32.dll", CharSet = CharSet.Auto)]
        public static extern int PostMessage(IntPtr hWnd, int msg, IntPtr wParam, IntPtr lParam);
 
        private void post()
        {

        }

        private void button1_Click(object sender, EventArgs e)
        {
            IntPtr ptr = FindWindow(null, "post messager B");
            if (ptr != IntPtr.Zero)
            {
                int msg = 9527;
                PostMessage(ptr, msg, IntPtr.Zero, IntPtr.Zero);
            }
        }
    }
}

PostMessage B端(接收端):

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 PostmessagerB

{

    public partial class Form1 : Form

    {

        public Form1()

        {

            InitializeComponent();

        }

        protected override void WndProc(ref Message m)

        {

            if (m.Msg == 9527)//m.Msg == MSG_SHOW

            {

                //label1.Text = (string)m.WParam.ToString();

                MessageBox.Show("9527");

            }

            base.WndProc(ref m);

        }

    }

}

至於為何可以使用SendMessage(),PostMessage(),FindWindow(),RegisterWindowMessage(),都是要先

import user32.dll (也就是[DllImport("user32.dll", SetLastError = true, CharSet = CharSet.Auto)] 後面為參數)

然後接收端使用WndProc (WindowProcess,我個人理解縮寫函意)去接收。

大部分程式碼也是參考網路上的,但大家都抄來抄去,而且我有修改程式碼,所以就不註明出處了(因為也不知道原始是誰的),當然我的版本是比較精簡化。

End