I haven't used the slider control before, so hopfully I am missing something simple. First,
using the follwing code, the slider value are not displayed: 

<telerik:RadSlider id="RadSlider1" runat="server" Height="95px"

ItemType="Tick" Length="300" MaximumValue="5" MinimumValue="1" Value="3" Width="400px" Skin="Windows7" TrackPosition="TopLeft" >

</telerik:RadSlider>


Thanks for you help.

<telerik:RadComboBox runat="server" ID="selecao" Width="450" AutoPostBack="true"
    LoadingMessage="Loading..." EmptyMessage="Expanda a hierarquia e selecione..." 
    OnClientDropDownOpened="OnClientDropDownOpenedHandler" EnableLoadOnDemand="true"
    MinFilterLength="3" OnInit="selecao_Init" OnItemsRequested="selecao_ItemsRequested" 
    OnClientItemsRequested="OnClientItemsRequested">
    <Items>
        <telerik:RadComboBoxItem Text="" Value="0"/>
    </Items>
    <ItemTemplate>
        <telerik:RadTreeView runat="server" ID="hierarquia" Width="300" 
            RegisterWithScriptManager="FALSE" 
            OnNodeExpand="hierarquia_NodeExpand" OnNodeClick="hierarquia_NodeClick"
            OnClientNodeClicking="nodeClicking" Skin="Default" CausesValidation="false" />
    </ItemTemplate>
</telerik:RadComboBox>

        protected void selecao_Init(object sender, EventArgs e)
        {
            if (this.Hierarquia.Nodes.Count == 0)
            {
                RadTreeNodeCollection parent = this.Hierarquia.Nodes;
                // load data
             }
 
            #region ClientScriptBlock
 
            ScriptManager.RegisterClientScriptBlock(this, typeof(FiltroGenerico), "FiltroGenerico", @"
 
                function nodeClicking(sender, args) {
                    var comboBox = $find(sender._clientStateFieldID.substring(0, sender._clientStateFieldID.length - 26));
                    var node = args.get_node()
 
                    var fullname = '';  // display full treename as requested
                    var pnode = node;
                    while(pnode != null && pnode.get_text != null)
                    {
                        fullname = ' > ' + pnode.get_text() + fullname;
                        pnode = pnode.get_parent();
                    }
                    fullname = fullname.substr(3)
 
                    comboBox.set_text(fullname);
                    comboBox.trackChanges();
                    comboBox.get_items().getItem(0).set_text(fullname);
                    comboBox.commitChanges();
 
                    comboBox.hideDropDown();
                    comboBox.attachDropDown();
                }
 
                function StopPropagation(e) {
                    if (!e)  e = window.event;
                    e.cancelBubble = true;
                }
 
                function OnClientItemsRequested(sender, eventArgs) {
                    var tree = sender.get_items().getItem(0).findControl('hierarquia');
tree.add_nodeClicking(nodeClicking);
                }
 
                function OnClientDropDownOpenedHandler(sender, eventArgs) {
                    var tree = sender.get_items().getItem(0).findControl('hierarquia');
                    var selectedNode = tree.get_selectedNode();
                    if (selectedNode) {
                        selectedNode.scrollIntoView();
                    }
                }", true);
 
            #endregion
        }