Sunday, November 14, 2010

Calling JavaScript function from WinForms and vice-versa

I'be been working on application that needs to load page and display it in WebBrowser control. Second requirement was to allow interaction between WinForms application and web page. After a couple of minutes of googling I found some important information that helped me to solve my problem. Here I will show a sample application where JavaScript function is called from WinForms application.

Hole process can be described by following steps:
  • Create Windows Forms application
  • Add WebBrowser control into Form
  • Create web page with JavaScript function you want to call

Calling JavaScript function from WinForms application isn't so difficult. WebBrowser constrol has property Document which gets an HtmlDocument representing the Web page currently displayed in the WebBrowser control.

You can use this property, in combination with the ObjectForScripting property, to implement two-way communication between a Web page displayed in the WebBrowser control and your application. Use the HtmlDocument.InvokeScript method to call script methods implemented in a Web page from your client application code. Your scripting code can access your application through the window.external object, which is a built-in DOM object provided for host access, and which maps to an object that you specify for the ObjectForScripting property.

          <script type="text/javascript">        

          function ShowMessage(message)
          function ShowWinFormsMessage() {
               var msg = document.getElementById('txtMessage').value;
               return window.external.ShowMessage(msg);
          <input type="text" id="txtMessage" />
          <input type="button" value="Show Message" onclick="ShowWinFormsMessage()" />

Two JavaScript functions are in sample page. function ShowMessage(message) is called from WinForms application and function ShowWinFormsMessage call ShowMessage(msg) C# function.

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 WebBrowserJavaScriptExample
    public partial class frmMain : Form
        public frmMain()
            webBrowser1.ObjectForScripting = new ScriptManager(this);

        private void btnShowMessage_Click(object sender, EventArgs e)
            object[] o = new object[1];
            object result = this.webBrowser1.Document.InvokeScript("ShowMessage", o);

        private void frmMain_Load(object sender, EventArgs e)

        public class ScriptManager
            frmMain _form;
            public ScriptManager(frmMain form)
                _form = form;

            public void ShowMessage(object obj)

More information about WebBrowser object ju can find here:

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