RadMessageBox displays a modal dialog box that contains a system icon, a set of buttons, and a brief application-specific message, such as status or error information. To display a message box, call the static method RadMessageBox.Show. The title, message, buttons, and icons displayed in the message box are determined by parameters that you pass to the method.
In the related Getting Started article you can find how to use the control with a sample scenario.
Download and check out the online demo at demos.telerik.com