Validation
You can use the built in ASP.NET validation with RadTreeView.
Validating the TreeView with RequiredFieldValidator
To validate for selected node of a TreeView, just specify the ID of the tree in the ControlToValidate property of the RequiredFieldValidator. Validation checks to see if there is at least one selected node.
<telerik:RadTreeView RenderMode="Lightweight" runat="server" ID="RadTreeView1">
<Nodes>
...
</Nodes>
</telerik:RadTreeView>
<asp:RequiredFieldValidator ID="RequiredFieldValidator1" ControlToValidate="RadTreeView1" runat="server" ErrorMessage="Please select a node">
</asp:RequiredFieldValidator>
If no node is selected, the validator detects an error and displays the error message:
Validating the TreeView using the CompareValidator
You can validate the TreeView using CompareValidator control. You need to specify the ID of the tree in the ControlToValidate property, the Operator and ValueToCompare properties. The validation will be made against the Value property of the nodes if they have values and if not - against their Text property.
<telerik:RadTreeView RenderMode="Lightweight" runat="server" ID="RadTreeView1" Skin="Hay">
<Nodes>
<telerik:RadTreeNode runat="server" Text="Australia" Value="RootItems">
<Nodes>
<telerik:RadTreeNode runat="server" Text="Sidney">
</telerik:RadTreeNode>
<telerik:RadTreeNode runat="server" Text="Brisbane">
</telerik:RadTreeNode>
</Nodes>
</telerik:RadTreeNode>
<telerik:RadTreeNode runat="server" Text="France" Value="RootItems">
<Nodes>
<telerik:RadTreeNode runat="server" Text="Paris">
</telerik:RadTreeNode>
</Nodes>
</telerik:RadTreeNode>
<telerik:RadTreeNode runat="server" Text="USA" Value="RootItems">
</telerik:RadTreeNode>
</Nodes>
</telerik:RadTreeView>
<asp:CompareValidator ID="CompareValidator1" runat="server" ControlToValidate="RadTreeView1" ErrorMessage="Please select a City" Operator="NotEqual" ValueToCompare="RootItems">
</asp:CompareValidator>
If a root nodes is selected, the validator detects an error and displays the error message:
Causing Validation
The TreeView can trigger validation of other controls on the form when it performs a post-back to the server. Simply set the CausesValidation property to True.
By default, all validators on the Web page must be successful before the postback can occur. You can limit the controls that must be validated when the TreeView performs a post-back, while still allowing other controls on the Web page to be validated, by using validation groups. The validator controls have ValidationGroup property as does RadTreeView. Validation will be triggered only for the Validator controls where the ValidationGroup property matches the RadTreeView ValidationGroup. (If no ValidationGroup is set for the controls all Validators will be triggered.)
For a live example, see Validation Groups