Question

The Telerik DatePicker does not support the WebForms CompareValidator’s data type check, because when an invalid date is entered, the DatePicker shows an error style on the input box, but returns an empty value. So on a data entry form with optional date fields, some method is required to handle invalid dates so that they do not appear on postback to be empty fields.

Answer 1

By using a CustomValidator, we can check if the DatePicker has a value in the input text box but returns an empty string – this indicates the date format is invalid.

function DateValidate(sender, args) {
   var datepicker = document.getElementById(sender.controltovalidate).control;
   var dateInput = datepicker.get_dateInput();
   args.IsValid = !(dateInput.get_textBoxValue() != "" && dateInput.get_value() == "");
}

<telerik:RadDatePicker
   ID="RetiredDatePicker" dbSelectedDate='<%# Bind("RetiredDate") %>' Runat="server">
</telerik:RadDatePicker>
<asp:CustomValidator
   ID="RetiredDateValidator" runat="server" CssClass="Error" 
   ClientValidationFunction="DateValidate" ValidateEmptyText="true"
   ControlToValidate="RetiredDatePicker"  SetFocusOnError="True" 
   ErrorMessage="Retired date is not a valid date">*</asp:CustomValidator>