The SelectionChanged event is fired before Page_Load, hence when the ViewState is applied, it overrides the changes made inside the OnSelectionChanged handler.
Example - Clearing the CheckBox selection of a RadComboBox inside SelectionChanged
Workaround - Create a custom boolean property on the page and set it to true inside the SelectionChanged. Then, in Page_Load or the OnLoad event of any control, execute your logic based on the custom boolean property value.
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>
Scenario 1)
- Set MultiSelect1.Enabled=false;
- Do a postback;
Expected: MultiSelect remain disabled
Actual: MultiSelect gets enabled
Workaround: set MultiSelect1.Enable = false instead of .Enabled.
Scenario 2)
- Add a MultiSelect inside asp:Panel
- Disable the asp:Panel
Expected: MultiSelect is disabled
Actual: MultiSelect remains enabled
<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>