RadDatePicker Invalid Date Alert Box
There is no validator in .net that validate raddatepicker's invalid date. in this case we should use raddatepicker's client event on error. <telerik:RadDatePicker runat="server" ID="rdpStartDate"> <DateInput runat="server"> <ClientEvents OnError=" ValidateDate " /> </DateInput> </telerik:RadDatePicker> JavaScript function ValidateDate (sender,args) { var reason = args.get_reason(); if (reason === 1) { alert("Invalid Date"); } ...