Call a C# Method From JavaScript Hosted in a WebBrowser

AspDotNetDev

4.93/5 (19 votes)

Nov 23, 2010

CPOL

175092

This demonstrates how you can call a C# method in a Windows Forms application from JavaScript that is hosted in a webpage inside a WebBrowser control on your form.

This sample demonstrates how to call C# from JavaScript. It also shows that parameters can be passed to C# methods. First, create a Windows Forms application. Then, add a WebBrowser control to your form. Then modify the code for the form so it looks like this:

namespace WindowsFormsApplication6
{
    // This first namespace is required for the ComVisible attribute used on the ScriptManager class.
    using System.Runtime.InteropServices;
    using System.Windows.Forms;

    // This is your form.
    public partial class Form1 : Form
    {
        // This nested class must be ComVisible for the JavaScript to be able to call it.
        [ComVisible(true)]
        public class ScriptManager
        {
            // Variable to store the form of type Form1.
            private Form1 mForm;

            // Constructor.
            public ScriptManager(Form1 form)
            {
                // Save the form so it can be referenced later.
                mForm = form;
            }

            // This method can be called from JavaScript.
            public void MethodToCallFromScript()
            {
                // Call a method on the form.
                mForm.DoSomething();
            }

            // This method can also be called from JavaScript.
            public void AnotherMethod(string message)
            {
                MessageBox.Show(message);
            }
        }

        // This method will be called by the other method (MethodToCallFromScript) that gets called by JavaScript.
        public void DoSomething()
        {
            // Indicate success.
            MessageBox.Show("It worked!");
        }

        // Constructor.
        public Form1()
        {
            // Boilerplate code.
            InitializeComponent();

            // Set the WebBrowser to use an instance of the ScriptManager to handle method calls to C#.
            webBrowser1.ObjectForScripting = new ScriptManager(this);

            // Create the webpage.
            webBrowser1.DocumentText = @"<html>
                <head>
	                <title>Test</title>
                </head>
                <body>
	            <input type=""button"" value=""Go!"" onclick=""window.external.MethodToCallFromScript();"" />
                    <br />
                    <input type=""button"" value=""Go Again!"" onclick=""window.external.AnotherMethod('Hello');"" />
                </body>
                </html>";
        }
    }
}

Note that your application may be part of a namespace other than WindowsFormsApplication6, but the rest of the code should work if you follow the above instructions explicitly. I created this tip/trick because somebody asked me a question and they didn't understand this sample that I sent them to. This tip/trick makes the sample more understandable by fixing the two bugs I spotted, adding the using statements that weren't mentioned, and by heavily commenting the code. Hopefully the rest of you will find this of use as well.