WatiN Javascript Alert Dialog Handler

The javascript alert handler that comes with WatiN out of the box didn’t quite do what I wanted. I needed something that could be automatically running the whole time and dismiss the alert whenever it happens but notify my code that the alert had happened and what the alert message had been. So I came up with the following modification to the WatiN version which suits my purpose:

    public class JavaScriptAlertDialogHandler : BaseDialogHandler
    {
        private readonly Action _onAlert;

        public JavaScriptAlertDialogHandler(Action onAlert)
        {
            _onAlert = onAlert;
        }

        public override bool HandleDialog(Window window)
        {
            if (CanHandleDialog(window))
            {
                _onAlert(window.Message);
                new WinButton(GetOKButtonId(), window.Hwnd).Click();
                return true;
            }
            return false;
        }

        public override bool CanHandleDialog(Window window)
        {
            return (window.StyleInHex == "94C801C5" && !ButtonWithId1Exists(window.Hwnd));
        }

        private static int GetOKButtonId()
        {
            return 2;
        }

        protected static bool ButtonWithId1Exists(IntPtr windowHwnd)
        {
            var button = new WinButton(1, windowHwnd);
            return button.Exists();
        }
    }

So when you construct the handler you pass in an Action that will receive the text of the message when the handler handles an alert e.g.

    IE.AddDialogHandler(new JavaScriptAlertDialogHandler(s => ScriptAlert = s));

Hope this is of some use to someone else too …