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ASP.NET Validators Support

In this article, you will learn how to integrate the native ASP.NET validation control with RadRadioButtonList.

As of the R1 2017 release, there is built-in support for the RequiredFieldValidator control. Older versions can be integrated with the CustomValidator control as an alternative solution (see Example 2).

The RadRadioButtonList control support the following types of validation:

Validation on the Server

RadRadioButton list can be validated easily during a postback in the server code. You can do this with either a RequiredFieldValidator, or with a CustomValidator.

Using RequiredFieldValidator

To use the RequiredFieldValidator, you just need to set the ControlToValidate property to the RadioButtonList's ID. This will trigger validation when the user submits and the validation control will validate against the SelectedItem property and return the appropriate validation result.

Example 1: Configuring RequiredFieldValidator control with RadioButtonList.

<telerik:RadRadioButtonList runat="server" ID="RadRadioButtonList1" AutoPostBack="false">
    <Items>
        <telerik:ButtonListItem Text="Option 1" Value="0" />
        <telerik:ButtonListItem Text="Option 2" Value="1" />
        <telerik:ButtonListItem Text="Option 3" Value="2" />
    </Items>
</telerik:RadRadioButtonList>

<asp:RequiredFieldValidator ID="RequiredFieldValidator1" runat="server" 
    ControlToValidate="RadRadioButtonList1"
    ErrorMessage="Please choose at least one of the options displayed" />

Using CustomValidator

As an alternative to the RequiredFieldValidator, you can use CustomValidator and have your own logic that validates the RadioButtonList.

Example 2: Configuring CustomValidator control with RadioButtonList.

<telerik:RadRadioButtonList runat="server" ID="RadRadioButtonList1" AutoPostBack="false">
    <Items>
        <telerik:ButtonListItem Text="Option 1" Value="0" />
        <telerik:ButtonListItem Text="Option 2" Value="1" />
        <telerik:ButtonListItem Text="Option 3" Value="2" />
    </Items>
</telerik:RadRadioButtonList>

<asp:CustomValidator ID="CustomButtonListValidator" runat="server" 
    ErrorMessage="Please choose at least one of the options displayed"
    OnServerValidate="CustomButtonListValidator_ServerValidate" />
protected void CustomButtonListValidator_ServerValidate(object source, ServerValidateEventArgs args)
{
    args.IsValid = (RadRadioButtonList1.SelectedIndex > -1);
}
Protected Sub CustomButtonListValidator_ServerValidate(source As Object, args As ServerValidateEventArgs)
    args.IsValid = (RadRadioButtonList1.SelectedIndex > -1)
End Sub

Validation on the Client

The validation on the client without a postback can be achieved only with CustomValidators.

Example 3: Configuring client-side validation with CustomValidator control for RadioButtonList.

<telerik:RadRadioButtonList runat="server" ID="RadRadioButtonList1"  ValidationGroup="RadioButtonList" AutoPostBack="false">
    <Items>
        <telerik:ButtonListItem Text="Option 1" Value="0" />
        <telerik:ButtonListItem Text="Option 2" Value="1" />
        <telerik:ButtonListItem Text="Option 3" Value="2" />
    </Items>
</telerik:RadRadioButtonList>
    <asp:CustomValidator ID="CustomValidator1" ValidationGroup="RadioButtonList" ControlToValidate="RadRadioButtonList1" runat="server"
                ErrorMessage="Please choose at least one of the options displayed" EnableClientScript="true"
                ClientValidationFunction="customValidationFunction" />
<telerik:RadButton runat="server" AutoPostBack="true" Text="Submit" ValidationGroup="RadioButtonList" />
<script>
    function customValidationFunction(sender, args) {
        var rarioButtonList = $find(sender.controltovalidate);
        if (rarioButtonList && rarioButtonList.get_selectedIndex() < 0) {
            args.IsValid = false;
        }
    }
</script>

See Also