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Editorial Team
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Asked: 2026-05-16T17:43:32+00:00

I have a C# WinForms application that has a WebBrowser control inside of it.

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I have a C# WinForms application that has a WebBrowser control inside of it. I would like to perform two-way communication between my C# form and the JavaScript within the embedded web browser control.

I know I can invoke a JavaScript function with InvokeScript, but how can I invoke C# code from JavaScript in a Document? I guess it wont be easy due to security, but is it possible, somehow, anyhow?
These JavaScript functions are supposed to be user functions, pretty much like macros, that would tell the WebBrowser exactly what to do with the help of a whole C# library written by myself. And since this is for a web scraper, JavaScript is the perfect language for these macros since it is pretty much made to access elements in an HTML document.

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1 Answer

  1. Editorial Team

    What you need to do is set the ObjectForScripting property on the web browser control to an object containing the C# methods you want to call from JavaScript. Then you can access that object from JavaScript using window.external. The only thing to watch out for is that the object has to have the [ComVisibleAttribute(true)] attribute. I’ve used this successfully for several years.

    Here’s a page with documenation and a simple example: http://msdn.microsoft.com/en-us/library/a0746166.aspx

    Here’s the example from the link (I haven’t tried this code):

    using System;
using System.Windows.Forms;
using System.Security.Permissions;

[PermissionSet(SecurityAction.Demand, Name="FullTrust")]
[System.Runtime.InteropServices.ComVisibleAttribute(true)]
public class Form1 : Form
{
    private WebBrowser webBrowser1 = new WebBrowser();
    private Button button1 = new Button();

    [STAThread]
    public static void Main()
    {
        Application.EnableVisualStyles();
        Application.Run(new Form1());
    }

    public Form1()
    {
        button1.Text = "call script code from client code";
        button1.Dock = DockStyle.Top;
        button1.Click += new EventHandler(button1_Click);
        webBrowser1.Dock = DockStyle.Fill;
        Controls.Add(webBrowser1);
        Controls.Add(button1);
        Load += new EventHandler(Form1_Load);
    }

    private void Form1_Load(object sender, EventArgs e)
    {
        webBrowser1.AllowWebBrowserDrop = false;
        webBrowser1.IsWebBrowserContextMenuEnabled = false;
        webBrowser1.WebBrowserShortcutsEnabled = false;
        webBrowser1.ObjectForScripting = this;
        // Uncomment the following line when you are finished debugging.
        //webBrowser1.ScriptErrorsSuppressed = true;

        webBrowser1.DocumentText =
            "<html><head><script>" +
            "function test(message) { alert(message); }" +
            "</script></head><body><button " +
            "onclick=\"window.external.Test('called from script code')\">" +
            "call client code from script code</button>" +
            "</body></html>";
    }

    public void Test(String message)
    {
        MessageBox.Show(message, "client code");
    }

    private void button1_Click(object sender, EventArgs e)
    {
        webBrowser1.Document.InvokeScript("test",
            new String[] { "called from client code" });
    }
}
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