A possible way to change dynamically the source of the MediaPlayer in asp web application is to use the media player along with other Silverlight controls. For example a buttons, that will change the videos when clicked. Please examine the described approach and let us know if it works for you.
Please also note that in ASP 4 , the <asp:Silverlight> is no more used and it is replaced by the <object> tag. Feel free to ask if you need further assistance.
All the best,
the Telerik team
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