C Implementation Method Example for Sending Messages Between Applications

  • 2021-12-21 04:46:47
  • OfStack

This article illustrates the C # implementation of sending messages between applications. Share it for your reference, as follows:

Start by creating two C # application projects.

The first project contains one Windows Form (Form1), one Button and one TextBox on top of Form1.

The second project contains one Windows Form (Form1) and two Button on Form1 to test the Click event of Button in the first application and modify the value of TextBox in the first application.

The code for Form in the first application is as follows:


using System;
using System.Drawing;
using System.Collections;
using System.ComponentModel;
using System.Windows.Forms;
public class Form1 : System.Windows.Forms.Form {
 private System.Windows.Forms.Button button1;
 private System.Windows.Forms.TextBox textBox1;
 private System.ComponentModel.Container components = null;
 [STAThread]
 static void Main() {
 Application.Run(new Form1());
 }
 public Form1()
 {
 InitializeComponent();
 }
 protected override void Dispose( bool disposing )
 {
 if( disposing )
 {
 if(components != null)
 {
 components.Dispose();
 }
 }
 base.Dispose( disposing );
 }
 #region Windows  Code Generated by Form Designer 
 private void InitializeComponent()
 {
 this.button1 = new System.Windows.Forms.Button();
 this.textBox1 = new System.Windows.Forms.TextBox();
 this.SuspendLayout();
 //
 // button1
 //
 this.button1.Location = new System.Drawing.Point(32, 24);
 this.button1.Name = "button1";
 this.button1.TabIndex = 0;
 this.button1.Text = "button1";
 this.button1.Click += new System.EventHandler(this.button1_Click);
 //
 // textBox1
 //
 this.textBox1.Location = new System.Drawing.Point(32, 64);
 this.textBox1.Name = "textBox1";
 this.textBox1.TabIndex = 1;
 this.textBox1.Text = "textBox1";
 //
 // Form1
 //
 this.AutoScaleBaseSize = new System.Drawing.Size(6, 14);
 this.ClientSize = new System.Drawing.Size(292, 266);
 this.Controls.Add(this.textBox1);
 this.Controls.Add(this.button1);
 this.Name = "Form1";
 this.Text = "Form1";
 this.ResumeLayout(false);
 }
 #endregion
 private void button1_Click(object sender, System.EventArgs e) {
 MessageBox.Show("This is button1 click!");
 }
}

The code for Form in the second application is as follows:


using System;
using System.Text;
using System.Drawing;
using System.Collections;
using System.ComponentModel;
using System.Windows.Forms;
using System.Runtime.InteropServices;
public class TestForm1 : System.Windows.Forms.Form {
 private System.Windows.Forms.Button button1;
 private System.Windows.Forms.Button button2;
 private System.ComponentModel.Container components = null;
 [STAThread]
 static void Main() {
 Application.Run(new TestForm1());
 }
 public TestForm1()
 {
 InitializeComponent();
 }
 protected override void Dispose( bool disposing )
 {
 if( disposing )
 {
 if(components != null)
 {
 components.Dispose();
 }
 }
 base.Dispose( disposing );
 }
 #region Windows  Code Generated by Form Designer 
 private void InitializeComponent()
 {
 this.button1 = new System.Windows.Forms.Button();
 this.button2 = new System.Windows.Forms.Button();
 this.SuspendLayout();
 //
 // button1
 //
 this.button1.Location = new System.Drawing.Point(32, 24);
 this.button1.Name = "button1";
 this.button1.TabIndex = 0;
 this.button1.Text = "button1";
 this.button1.Click += new System.EventHandler(this.button1_Click);
 //
 // button2
 //
 this.button2.Location = new System.Drawing.Point(32, 64);
 this.button2.Name = "button2";
 this.button2.TabIndex = 0;
 this.button2.Text = "button2";
 this.button2.Click += new System.EventHandler(this.button2_Click);
 //
 // TestForm1
 //
 this.AutoScaleBaseSize = new System.Drawing.Size(6, 14);
 this.ClientSize = new System.Drawing.Size(292, 266);
 this.Controls.Add(this.button1);
 this.Controls.Add(this.button2);
 this.Name = "TestForm1";
 this.Text = "TestForm1";
 this.ResumeLayout(false);
 }
 #endregion
 private void button1_Click(object sender, System.EventArgs e) {
 IntPtr hwnd_win ;
 IntPtr hwnd_button ;
 hwnd_win = FindWindow("WindowsForms10.Window.8.app3","Form1");
 hwnd_button = FindWindowEx(hwnd_win ,new IntPtr(0) ,"WindowsForms10.BUTTON.app3","button1");
 const int BM_CLICK = 0x00F5;
 Message msg = Message.Create(hwnd_button ,BM_CLICK ,new IntPtr(0),new IntPtr(0));
 PostMessage(msg.HWnd ,msg.Msg ,msg.WParam ,msg.LParam);
 }
 private void button2_Click(object sender, System.EventArgs e) {
 const int WM_CHAR = 0x0102;
 IntPtr hwnd_win ;
 IntPtr hwnd_textbox ;
 hwnd_win = FindWindow("WindowsForms10.Window.8.app3","Form1");
 hwnd_textbox = FindWindowEx(hwnd_win ,new IntPtr(0) ,"WindowsForms10.EDIT.app3","textBox1");
 string strtext = " Test aaa";
 UnicodeEncoding encode = new UnicodeEncoding();
 char[] chars = encode.GetChars(encode.GetBytes(strtext));
 Message msg ;
 foreach (char c in chars ) {
 msg = Message.Create(hwnd_textbox ,WM_CHAR ,new IntPtr(c),new IntPtr(0));
 PostMessage(msg.HWnd ,msg.Msg ,msg.WParam ,msg.LParam);
 }
 }
 [DllImport("user32.dll")]
 public static extern IntPtr FindWindow(string lpClassName, string lpWindowName);
 [DllImport("user32.dll")]
 public static extern IntPtr FindWindowEx(IntPtr hwndParent,IntPtr hwndChildAfter,string lpszClass,string lpszWindow);
 [DllImport("user32.dll",CharSet=CharSet.Unicode)]
 public static extern IntPtr PostMessage(IntPtr hwnd,int wMsg,IntPtr wParam,IntPtr lParam);
}

The above code can be compiled and run in VS. NET, or compiled using csc. exe, such as using the command line 1:


F:>csc.exe Form1.cs
F:>csc.exe TestForm1.cs

After compilation, two. exe files are generated.

First run the first program to display the Form1 form, and then run the second program to display the TestForm1 form.

Click the button1 button on the TestForm1 form (send a message to button1 on the Form1 form) and the dialog box prompts "This is button1 click!" .

Clicking the button2 button on the TestForm1 form (sending a message to textBox1 on the Form1 form) displays "Test aaa" on textBox1 on Form1.

For more readers interested in C # related content, please check the topics on this site: "WinForm Control Usage Summary", "C # Form Operation Skills Summary", "C # Data Structure and Algorithm Tutorial", "C # Common Control Usage Tutorial", "C # Object-Oriented Programming Introduction Tutorial" and "C # Programming Thread Use Skills Summary"

I hope this article is helpful to everyone's C # programming.


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