Blocking dialogs in .NET WebBrowser control

And for an easy way to inject that magic line of javascript, read how to inject javascript into webbrowser control.

Or just use this complete code:

private void InjectAlertBlocker() { HtmlElement head = webBrowser1.Document.GetElementsByTagName("head")[0]; HtmlElement scriptEl = webBrowser1.Document.CreateElement("script"); string alertBlocker = "window.alert = function () { }"; scriptEl.SetAttribute("text", alertBlocker); head.AppendChild(scriptEl); } 

Bulletproof alert blocker:

Browser.Navigated += new WebBrowserNavigatedEventHandler( (object sender, WebBrowserNavigatedEventArgs args) => { Action<HtmlDocument> blockAlerts = (HtmlDocument d) => { HtmlElement h = d.GetElementsByTagName("head")[0]; HtmlElement s = d.CreateElement("script"); IHTMLScriptElement e = (IHTMLScriptElement)s.DomElement; e.text = "window.alert=function(){};"; h.AppendChild(s); }; WebBrowser b = sender as WebBrowser; blockAlerts(b.Document); for (int i = 0; i < b.Document.Window.Frames.Count; i++) try { blockAlerts(b.Document.Window.Frames[i].Document); } catch (Exception) { }; } ); 

This sample assumes you have Microsoft.mshtml reference added, "using mshtml;" in your namespaces and Browser is your WebBrowser instance.

Why is it bulletproof? First, it handles scripts inside frames. Then, it doesn't crash when a special "killer frame" exists in document. A "killer frame" is a frame which raises an exception on attempt to use it as HtmlWindow object. Any "foreach" used on Document.Window.Frames would cause an exception, so safer "for" loop must be used with try / catch block.

Maybe it's not the most readable piece of code, but it works with real life, ill-formed pages.

You may have to customize some things, take a look at IDocHostUIHandler, and then check out some of the other related interfaces. You can have a fair amount of control, even to the point of customizing dialog display/ui (I can't recall which interface does this). I'm pretty sure you can do what you want, but it does require mucking around in the internals of MSHTML and being able to implement the various COM interfaces.

Some other ideas: http://msdn.microsoft.com/en-us/library/aa770041.aspx

IHostDialogHelper IDocHostShowUI 

These may be the things you're looking at implementing.

webBrowser1.ScriptErrorsSuppressed = true; 

Just add that to your entry level function. After alot of research is when I came across this method, and touch wood till now its worked. Cheers!!

window.showModelessDialog and window.showModalDialog can be blocked by implementing INewWindowManager interface, additionally code below show how to block alert dialogs by implementing IDocHostShowUI

public class MyBrowser : WebBrowser { [PermissionSetAttribute(SecurityAction.LinkDemand, Name = "FullTrust")] public MyBrowser() { } protected override WebBrowserSiteBase CreateWebBrowserSiteBase() { var manager = new NewWindowManagerWebBrowserSite(this); return manager; } protected class NewWindowManagerWebBrowserSite : WebBrowserSite, IServiceProvider, IDocHostShowUI { private readonly NewWindowManager _manager; public NewWindowManagerWebBrowserSite(WebBrowser host) : base(host) { _manager = new NewWindowManager(); } public int ShowMessage(IntPtr hwnd, string lpstrText, string lpstrCaption, int dwType, string lpstrHelpFile, int dwHelpContext, out int lpResult) { lpResult = 0; return Constants.S_OK; // S_OK Host displayed its UI. MSHTML does not display its message box. } // Only files of types .chm and .htm are supported as help files. public int ShowHelp(IntPtr hwnd, string pszHelpFile, uint uCommand, uint dwData, POINT ptMouse, object pDispatchObjectHit) { return Constants.S_OK; // S_OK Host displayed its UI. MSHTML does not display its message box. } #region Implementation of IServiceProvider public int QueryService(ref Guid guidService, ref Guid riid, out IntPtr ppvObject) { if ((guidService == Constants.IID_INewWindowManager && riid == Constants.IID_INewWindowManager)) { ppvObject = Marshal.GetComInterfaceForObject(_manager, typeof(INewWindowManager)); if (ppvObject != IntPtr.Zero) { return Constants.S_OK; } } ppvObject = IntPtr.Zero; return Constants.E_NOINTERFACE; } #endregion } } [ComVisible(true)] [Guid("01AFBFE2-CA97-4F72-A0BF-E157038E4118")] public class NewWindowManager : INewWindowManager { public int EvaluateNewWindow(string pszUrl, string pszName, string pszUrlContext, string pszFeatures, bool fReplace, uint dwFlags, uint dwUserActionTime) { // use E_FAIL to be the same as CoInternetSetFeatureEnabled with FEATURE_WEBOC_POPUPMANAGEMENT //int hr = MyBrowser.Constants.E_FAIL; int hr = MyBrowser.Constants.S_FALSE; //Block //int hr = MyBrowser.Constants.S_OK; //Allow all return hr; } } 

The InjectAlertBlocker is absolutely correct code is

private void InjectAlertBlocker() { HtmlElement head = webBrowser1.Document.GetElementsByTagName("head")[0]; HtmlElement scriptEl = webBrowser1.Document.CreateElement("script"); IHTMLScriptElement element = (IHTMLScriptElement)scriptEl.DomElement; string alertBlocker = "window.alert = function () { }"; element.text = alertBlocker; head.AppendChild(scriptEl); } 

References needed to be added is

1. Add a reference to MSHTML, which will probalby be called "Microsoft HTML Object Library" under COM references.

2. Add using mshtml; to your namespaces.

3. Get a reference to your script element's IHTMLElement:

Then you can use the Navigated event of webbrowser as:

private void InjectAlertBlocker() { HtmlElement head = webBrowser1.Document.GetElementsByTagName("head")[0]; HtmlElement scriptEl = webBrowser1.Document.CreateElement("script"); IHTMLScriptElement element = (IHTMLScriptElement)scriptEl.DomElement; string alertBlocker = "window.alert = function () { }"; element.text = alertBlocker; head.AppendChild(scriptEl); } private void webDest_Navigated(object sender, WebBrowserNavigatedEventArgs e) { InjectAlertBlocker(); } 

Are you trying to implement a web robot? I have little experience in using the hosted IE control but I did completed a few Win32 projects tried to use the IE control. Disabling the popups should be done via the event handlers of the control as you already did, but I found that you also need to change the 'Disable script debugging xxxx' in the IE options (or you could modify the registry in your codes) as cjheath already pointed out. However I also found that extra steps needed to be done on checking the navigating url for any downloadable contents to prevent those open/save dialogs. But I do not know how to deal with streaming files since I cannot skip them by looking at the urls alone and in the end I turned to the Indy library saving me all the troubles in dealing with IE. Finally, I remember Microsoft did mention something online that IE is not designed to be used as an OLE control. According to my own experience, every time the control navigates to a new page did introduce memory leaks for the programs!

I had bigger problems with this: loading a webpage that is meant for printing and it displays annoying Print dialog. The InjectBlocker was the only way that worked, but fairly unreliable. Under certain conditions (I am considering it's due that WebBrowser control uses IE engine and this depends on installed IE version) the print dialog still appears. This is a major problem, the solution works on Win7 with IE9 installed, but WinXP with IE8 displays the dialog, no matter what.

I believe the solution is in modifying source code and removing the print javascript, before control renders the page. However I tried that with: DocumentText property of the webbrowser control and it is not working. The property is not read only, but it has no effect, when I modify the source.

The solution I found for my problem is the Exec script:

string alertBlocker = "window.print = function emptyMethod() { }; window.alert = function emptyMethod() { }; window.open = function emptyMethod() { };"; this.Document.InvokeScript("execScript", new Object[] { alertBlocker, "JavaScript" }); 

I managed to inject the code above by creating an extended WebBroswer class and overriding the OnNavigated method.

This seemed to work quite well:

class WebBrowserEx : WebBrowser { public WebBrowserEx () { } protected override void OnNavigated( WebBrowserNavigatedEventArgs e ) { HtmlElement he = this.Document.GetElementsByTagName( "head" )[0]; HtmlElement se = this.Document.CreateElement( "script" ); mshtml.IHTMLScriptElement element = (mshtml.IHTMLScriptElement)se.DomElement; string alertBlocker = "window.alert = function () { }"; element.text = alertBlocker; he.AppendChild( se ); base.OnNavigated( e ); } } 

Simply from the browser control properties: scriptErrorSupressed=true

The easiest way to do this is : In the : Webbrowser Control you have the procedure ( standard ) BeforeScriptExecute

( The parameter for BeforeScriptExecute is pdispwindow )

Add this :

pdispwindow.execscript("window.alert = function () { }") 

In this way before any script execution on the page window alert will be suppressed by injected code.