add default item to RadComboBox

I am trying to add default item as 'All' at top of RadComboBox. How can I do this? I am using LoadOnDemand and load开发者_Go百科ing database items using WCF service.Please help. I am stuck with this.

Thanks..

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You can set the "EmptyMessage" property of the RadComboBox to "All". Take a look at this Telerik demo for an example.