Using the TargetControlID Property
The TargetControlID property specifies the ID of the element that should be 'tooltipified'. It can be set declaratively on the page:
<telerik:RadToolTip RenderMode="Lightweight" ID="RadToolTip1" runat="server" TargetControlID="Button1" IsClientID="true">
</telerik:RadToolTip>
or in the code-behind:
Button button1 = new Button();
button1.ID = "Button1";
RadToolTip1.TargetControlID = button1.ID;
Dim button1 As New Button()
button1.ID = "Button1"
RadToolTip1.TargetControlID = button1.ID
By default, RadToolTip assumes a server ID. If the ID is client-side, as in the case where an element is pure HTML and not a server control, then the IsClientID property should be set to True.
Button button1 = new Button();
button1.ID = "Button1";
RadToolTip1.TargetControlID = button1.ClientID;
RadToolTip1.IsClientID = true;
Dim button1 As New Button()
button1.ID = "Button1"
RadToolTip1.TargetControlID = button1.ClientID
RadToolTip1.IsClientID = True