Calling C# BHO methods from Javascript

Question

I\'m trying to figure out how to call C# methods in my BHO object from Javascript within the page. I found numerous pages on how to do it in C++/ATL/Com such as:

Bro

Answer 1

I hate to answer my own question, but I really feel like the community ought to know the answer because it is short, simple, and beautiful with C# 4.0 and SO many people seem to have this problem.

Make sure that you correctly expose the Browser Helper Object:

[ComVisible(true),
 Guid("DA8EA345-02AE-434E-82E9-448E3DB7629E"),
 ClassInterface(ClassInterfaceType.None), ProgId("MyExtension"),
 ComDefaultInterface(typeof(IExtension))]
public class BrowserHelperObject : IObjectWithSite, IExtension
{
    ...
    public int Foo(string s) { ... }
    ...
    public void OnDocumentComplete(dynamic frame, ref dynamic url)
    {
        ...
        dynamic window = browser.Document.parentWindow;
        IExpando windowEx = (IExpando)window;
        windowEx.AddProperty("myExtension");
        window.myExtension = this;
        ...
    }
    ...
}

And you will need a definition for your extensions:

[ComVisible(true),
 Guid("4C1D2E51-018B-4A7C-8A07-618452573E42"),
 InterfaceType(ComInterfaceType.InterfaceIsDual)]
public interface IExtension
{
    [DispId(1)]
    int Foo(string s);
    ...
}

You can access your Browser Helper Object in javascript thus:

var result = window.myExtension.Foo("bar");

or just

var result = myExtension.Foo("bar");

That's it. Stop banging your head against the wall and go celebrate!

Answer 2

Also, after you add property you need to make sure to release COM references of window and windowEx