How do I display a popup from a WebBrowser in another window I created?

The web browser control supports the NewWindow event to get notified about a popup window. The Winforms wrapper however does not let you do much with it, you can only cancel the popup. The native COM wrapper permits passing back a new instance of the web browser, that instance will then be used to display the popup.

Taking advantage of this requires some work. For starters, use Project + Add Reference, Browse tab and select c:\windows\system32\shdocvw.dll. That adds a reference to the native COM interface.

Create a form that acts as the popup form. Drop a WebBrowser on it and make its code look similar to this:

public partial class Form2 : Form {
    public Form2() {
        InitializeComponent();
    }
    public WebBrowser Browser {
        get { return webBrowser1; }
    }
}

The Browser property gives access to the browser that will be used to display the web page in the popup window.

Now back to the main form. Drop a WebBrowser on it and make its code look like this:

public partial class Form1 : Form {
    public Form1() {
        InitializeComponent();
        webBrowser1.Url = new Uri("http://google.com");
    }
    SHDocVw.WebBrowser nativeBrowser;
    protected override void OnLoad(EventArgs e) {
        base.OnLoad(e);
        nativeBrowser = (SHDocVw.WebBrowser)webBrowser1.ActiveXInstance;
        nativeBrowser.NewWindow2 += nativeBrowser_NewWindow2;
    }
    protected override void OnFormClosing(FormClosingEventArgs e) {
        nativeBrowser.NewWindow2 -= nativeBrowser_NewWindow2;
        base.OnFormClosing(e);
    }

    void nativeBrowser_NewWindow2(ref object ppDisp, ref bool Cancel) {
        var popup = new Form2();
        popup.Show(this);
        ppDisp = popup.Browser.ActiveXInstance;
    }
}

The OnLoad method obtains a reference to the native COM interface, then subscribes an event handler to the NewWindow2 event. I made sure to unsubscribe that event in the FormClosing event handler, not 100% sure if that's necessary. Better safe then sorry.

The NewWindow2 event handler is the crux, note that the first argument allows passing back an untyped reference. That should be the native browser in the popup window. So I create an instance of Form2 and Show() it. Note the argument to Show(), that ensures that the popup is an owned window. Substitute this as necessary for your app, I assume you'd want to create an MDI child window in your case.

Do beware that this event doesn't fire for the window displayed when Javascript uses alert(). The browser doesn't treat that window as an HTML popup and doesn't use a browser window to display it so you cannot intercept or replace it.

I found that the best way to do this was to implement/sink the NewWindow3 event

Add the reference to c:\windows\system32\shdocvw.dll as mentioned in the other answers here.

Add event handler

SHDocVw.WebBrowser wbCOMmain = (SHDocVw.WebBrowser)webbrowser.ActiveXInstance;
wbCOMmain.NewWindow3 += wbCOMmain_NewWindow3;

Event method

void wbCOMmain_NewWindow3(ref object ppDisp, 
                          ref bool Cancel, 
                          uint dwFlags, 
                          string bstrUrlContext, 
                          string bstrUrl)
{
    // bstrUrl is the url being navigated to
    Cancel = true; // stop the navigation

    // Do whatever else you want to do with that URL
    // open in the same browser or new browser, etc.
}

• Set "Embed Interop Types" for the "Interop.SHDocVw" assembly to false
• Set the "local copy" to true.

Source for that help MSDN Post

Refining Hans answer, you can derive the WebBrowser for accessing the COM without adding the reference. It is by using the unpublished Winforms WebBrowser.AttachInterface and DetachInterface methods.

More elaborated here.

Here is the code:

Usage (change your WebBrowser instance to WebBrowserNewWindow2)

public partial class Form1 : Form
{
    public Form1()
    {
        InitializeComponent();
        this.webBrowser1.NewWindow2 += webBrowser_NewWindow2;
    }

    protected override void OnFormClosing(FormClosingEventArgs e)
    {
        webBrowser1.NewWindow2 -= webBrowser_NewWindow2;
        base.OnFormClosing(e);
    }

    void webBrowser_NewWindow2(object sender, WebBrowserNewWindow2EventArgs e)
    {
        var popup = new Form1();
        popup.Show(this);
        e.PpDisp = popup.Browser.ActiveXInstance;
    }
    public WebBrowserNewWindow2 Browser
    {
        get { return webBrowser1; }
    }
}

Code:

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

namespace SHDocVw
{
    public delegate void WebBrowserNewWindow2EventHandler(object sender, WebBrowserNewWindow2EventArgs e);

    public class WebBrowserNewWindow2EventArgs : EventArgs
    {
        public WebBrowserNewWindow2EventArgs(object ppDisp, bool cancel)
        {
            PpDisp = ppDisp;
            Cancel = cancel;
        }

        public object PpDisp { get; set; }
        public bool Cancel { get; set; }
    }

    public class WebBrowserNewWindow2 : WebBrowser
    {
        private AxHost.ConnectionPointCookie _cookie;
        private WebBrowser2EventHelper _helper;

        [PermissionSet(SecurityAction.LinkDemand, Name = "FullTrust")]
        protected override void CreateSink()
        {
            base.CreateSink();

            _helper = new WebBrowser2EventHelper(this);
            _cookie = new AxHost.ConnectionPointCookie(
                this.ActiveXInstance, _helper, typeof(DWebBrowserEvents2));
        }

        [PermissionSetAttribute(SecurityAction.LinkDemand, Name = "FullTrust")]
        protected override void DetachSink()
        {
            if (_cookie != null)
            {
                _cookie.Disconnect();
                _cookie = null;
            }
            base.DetachSink();
        }

        public event WebBrowserNewWindow2EventHandler NewWindow2;

        private class WebBrowser2EventHelper : StandardOleMarshalObject, DWebBrowserEvents2
        {
            private readonly WebBrowserNewWindow2 _parent;

            public WebBrowser2EventHelper(WebBrowserNewWindow2 parent)
            {
                _parent = parent;
            }

            public void NewWindow2(ref object pDisp, ref bool cancel)
            {
                WebBrowserNewWindow2EventArgs arg = new WebBrowserNewWindow2EventArgs(pDisp, cancel);
                _parent.NewWindow2(this, arg);
                if (pDisp != arg.PpDisp)
                    pDisp = arg.PpDisp;
                if (cancel != arg.Cancel)
                    cancel = arg.Cancel;
            }
        }

        [ComImport, Guid("34A715A0-6587-11D0-924A-0020AFC7AC4D"),
        InterfaceType(ComInterfaceType.InterfaceIsIDispatch),
        TypeLibType(TypeLibTypeFlags.FHidden)]
        public interface DWebBrowserEvents2
        {
            [DispId(0xfb)]
            void NewWindow2(
                [In, Out, MarshalAs(UnmanagedType.IDispatch)] ref object ppDisp,
                [In, Out] ref bool cancel);
        }
    }
}