Change Background on Invalid Fields

.NET doesn't provide a way to change the background color (or other attributes) of fields that fail validation when using the built-in validators. I think color prompting is a nice way to indicate bad user input, so rather than going to a whole lot of code-behind nonsense you can just shim on to the .NET validation display routine by putting this javascript on your ASPX page:

var OriginalValidatorUpdateDisplay = null;

function NewValidatorUpdateDisplay(val) {
    OriginalValidatorUpdateDisplay(val);
    if (val.controltovalidate) {
        var ctrlIsValid=true;
        var ctrl = document.getElementById(val.controltovalidate);
        for (var i = 0; i < ctrl.Validators.length; i++) {
            if (!ctrl.Validators[i].isvalid) {
                ctrlIsValid = false;
            }
        }
        if (ctrlIsValid) {
            ctrl.style.backgroundColor = '';
            ctrl.style.color = '';
        }
        else {
            ctrl.style.backgroundColor = '#FF0000';
            ctrl.style.color = '#FFFFFF';
        }
    }
}

if (typeof (ValidatorUpdateDisplay) == 'function') {
    OriginalValidatorUpdateDisplay = ValidatorUpdateDisplay;
    ValidatorUpdateDisplay = NewValidatorUpdateDisplay;
} 

That's it!

The only downside is that as-written there is only one "pass" and one "fail" attribute per page. You could change classes on the fly and accomplish more customization, but that sort of violates the elegance of this approach.

Visual Studio GridView designer bug

There is a bug in Visual Studio 2008 that prevents property changes in design view from being reflected back to source code when controls are embedded in wizards or master pages. For simple controls this is not a big deal, but for complex controls, like DevExpress's ASPxGridView, the designer is a huge time saver -- which is the only reason you pay good money for a nice RAD toolkit in the first place.

Luckily, there is a hotfix:
http://connect.microsoft.com/VisualStudio/Downloads/DownloadDetails.aspx?DownloadID=17185

Get it.