RadToolTip for RadComboBox

HOW-TO

Tooltipify each element of a RadComboBox

SOLUTION

The standard asp DropDownList control cannot be configured to display even the plain [browser] tooltip due to having OPTION elements in its HTML representation and the OPTION element is not a real HTML object.

Tooltipifying a RadComboBox, however, is possible and pretty easy. In order to achieve the desired behavior you should simply pu a** RadToolTip** control in the Item Template of the RadComboBox as shown below:

ASP.NET

<telerik:RadComboBox ID="RadComboBox1" runat="server" DataSourceID="AccessDataSource1" 
            DataTextField="ContactName">  
    <ItemTemplate> 
        <asp:Label runat="server" ID="Label1" Text='<%# Eval("ContactName")%> '></asp:Label> 
        <telerik:RadToolTip ID="RadToolTip1" runat="server" Width="100" Height="10" TargetControlID="Label1" 
            Position="BottomRight" Text='<%# Eval("ContactName")%>'>  
        </telerik:RadToolTip> 
    </ItemTemplate> 
    <CollapseAnimation Duration="200" Type="OutQuint" /> 
</telerik:RadComboBox> 

In case you want to have a single RadToolTip for the whole RadComboBox control, you should simply set its ID as a TargetControlID of the RadToolTip:

ASP.NET

<telerik:RadToolTip ID="RadToolTip1" runat="server" Width="100" Height="10" Position="BottomRight" 
    Text='This is a single tooltip for the whole RadComboBox control' TargetControlID="RadComboBox1">  
</telerik:RadToolTip>

NOTE: If you are using load-on-demand, adding RadToolTip control instances to the items will not work. The load-on-demand mechanism is either a web service or a page callback, and neither of them can return IScriptControl instances and the MS AJAX-generated scripts ($create() statement) needed for them to work.
When using load-on-demand, you can add a mouseover DOM event handler for the items that will show a tooltip with JavaScript (see the Dynamic Tooltip Creation demo). If you do not need or want to fetch the data for the tooltips dynamically, you can use a single tooltip instance outside of the combo box and its client-side API (see the set_text() method) to provide a text that can be rendered in the DOM of the item and obtained by the mouseover handler.