Unplanned
Last Updated: 22 Jun 2020 17:19 by ADMIN
<telerik:RadFormDecorator ID="RadFormDecorator1" runat="server" RenderMode="Lightweight" DecoratedControls="All" />
<telerik:RadMultiSelect runat="server"
    AutoClose="false"
    Placeholder="Select attendees..."
    DataTextField="text"
    DataValueField="text"
    Width="400px"
    ID="RadMultiSelect2">
    <Items>
        <telerik:MultiSelectItem Text="Steven White"></telerik:MultiSelectItem>
        <telerik:MultiSelectItem Text="Nancy King"></telerik:MultiSelectItem>
        <telerik:MultiSelectItem Text="Nancy Davolio"></telerik:MultiSelectItem>
    </Items>
</telerik:RadMultiSelect>
Unplanned
Last Updated: 25 May 2020 11:26 by ADMIN

A "Control 'RadMultiSelect1' referenced by the ControlToValidate property of 'MultiSelectValidator1' cannot be validated" error is thrown when the RadMultiSelect id is passed to the ControlToValidate property of the RequiredFieldValidator or CustomValidator.

Workaround: Using a CustomValidator with no ControlToValidate

<telerik:RadMultiSelect ID="RadMultiSelect1" runat="server" DataTextField="text" DataValueField="value">
    <Items>
        <telerik:MultiSelectItem Text="Item 1" Value="1"></telerik:MultiSelectItem>
        <telerik:MultiSelectItem Text="Item 2" Value="2"></telerik:MultiSelectItem>
        <telerik:MultiSelectItem Text="Item 3" Value="3"></telerik:MultiSelectItem>
    </Items>
</telerik:RadMultiSelect>

<telerik:RadButton runat="server" ID="RadButton1" Text="Postback" AutoPostBack="true" />

<asp:CustomValidator ErrorMessage="Please select an item" ClientValidationFunction="ClientValidationFunction" runat="server" />
<script>
    function ClientValidationFunction(sender, args) {
        var multiselect = $find("<%= RadMultiSelect1.ClientID %>");

        if (multiselect.get_value().length == 0) {
            args.IsValid = false;
        }
    }
</script>