Actually, we've had this feature implemented in one of the first versions of the RadWindow control (RadWindow for ASP.NET v1.x). We removed it however, due to customers' complaints. The problem is that a lot of users that work with corporate applications, don't have multimedia enabled on their PCs. Whenever these customers had a radalert / radconfirm / radprompt dialog opened in their browsers, they got a warning message from the browser about a missing multimedia plugin.
If you want to add such feature to our dialogs, you can use custom templates (more information on the subject is available here
). What you can do is to simply embed a wave file in the template's code and it will be played whenever that popup is displayed.
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