Call a C# Method From JavaScript Hosted in a WebBrowser

AspDotNetDev

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6 May 2011CPOL

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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.

License

This article, along with any associated source code and files, is licensed under The Code Project Open License (CPOL)