Load-On-Demand RadComboBox does not raise CustomValidator.ServerValidate when blank

[Wyatt]

Following this documentation, I am requiring that a value be set in a Load-On-Demand RadComboBox.  Both the client and server validation events are raised when text has been entered.  If there is no text, neither the client nor the server validation events are raised.  Also of note, MarkFirstMatch = True, ShowMoreResultsBox = True, and EnableVirtualScrolling = True.

I was able to fix this problem by adding a RequiredFieldValidator in addition to the CustomValidation.  Is this by design?

[Kalina]

Hello Wyatt,

You can use the CustomValidator control to validate the RadComboBox upon value and at the same time - to validate if the RadComboBox input is empty. 

Here is one basic sample to illustrate the approach:

<telerik:RadComboBox ID="RadComboBox1"  AllowCustomText="true"
    EnableLoadOnDemand="true"
    OnItemsRequested="RadComboBox1_OnItemsRequested"
    MarkFirstMatch="true"
    ShowMoreResultsBox="true"
    EnableVirtualScrolling="true"
    runat="server">

</telerik:RadComboBox>
<asp:Button ID="btnTSubmit" runat="server"
    CausesValidation="true" Text="Submit" />
<asp:CustomValidator ID="CustomValidator1" runat="server"
    ClientValidationFunction="validateCombo"
    ErrorMessage="You must select an item with even value"
    OnServerValidate="CustomValidator1_ServerValidate">
</asp:CustomValidator>

<script type="text/javascript">
    function validateCombo(source, args) {
        debugger
        args.IsValid = false;
        var combo = $find("<%= RadComboBox1.ClientID %>");

        var text = combo.get_text();
        if (text.length < 1) {
            args.IsValid = false;
        }
        else {
            var node = combo.findItemByText(text);
            if (node) {
                var value = node.get_value();
                if (value.length > 0 && value % 2 == 0) {
                    args.IsValid = true;
                }
            }
            else {
                args.IsValid = false;
            }
        }
    }
</script>

protected void RadComboBox1_OnItemsRequested(object sender, RadComboBoxItemsRequestedEventArgs e)
{

    this.RadComboBox1.Items.Add( new RadComboBoxItem("-- Select item --"));
    this.RadComboBox1.Items.Add(new RadComboBoxItem("Item with No Value"));
    this.RadComboBox1.Items.Add(new RadComboBoxItem("Item with Value=1", "1"));
    this.RadComboBox1.Items.Add(new RadComboBoxItem("Item with Value=2", "2"));
    this.RadComboBox1.Items.Add(new RadComboBoxItem("Item with Value=3", "3"));
    this.RadComboBox1.Items.Add(new RadComboBoxItem("Item with Value=4", "4"));


}

Please note that if you use the RadComboBox control to raise the PostBack event (by setting the AutoPostBack to "true") -  naturally there will be no PostBack raised and the CustomValidator will not fire.

All the best,
Kalina
the Telerik team

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[Eric Villemure]

Hi, I think I've had the same problem as yours.

I've found the solution here http://www.telerik.com/community/forums/aspnet-ajax/combobox/bug-custom-validation-in-particular-situation.aspx

Let me know if it helps