gistfile1.cs

using System;
using System.Windows.Forms;

namespace ConsoleApplication
{
    class Program
    {
        [STAThread]
        static void Main(string[] args)
        {
            var browser = new WebBrowser { ScriptErrorsSuppressed = true };
            browser.Navigate("");
            dynamic window = browser.Document.Window.DomWindow;
            window.execScript("function foo() { }; foo.prototype.run = function() { return 10; };function bar() { return new foo(); }");
            var z = ((dynamic)window.bar()).run(); // will crash here
        }
    }
}