public class ASPxSplitter :
    ASPxWebControl,
    IRequiresLoadPostDataControl,
    IEndInitAccessorContainer,
    IControlDesigner

Public Class ASPxSplitter
    Inherits ASPxWebControl
    Implements IRequiresLoadPostDataControl,
               IEndInitAccessorContainer,
               IControlDesigner

<dx:ASPxSplitter ID="splitter" runat="server">
    <Panes>
        <dx:SplitterPane>
            <ContentCollection>
                <dx:SplitterContentControl runat="server">
                    <dx:ASPxNavBar runat="server" AllowSelectItem="True" Target="contentUrlPane"
                        ID="navBar">
                        <Groups>
                            <dx:NavBarGroup Text="Sample Pages">
                                <Items>
                                    <dx:NavBarItem NavigateUrl="SamplePages/Page1.aspx" Text="Page 1">
                                    </dx:NavBarItem>
                                    <dx:NavBarItem NavigateUrl="SamplePages/Page2.aspx" Selected="True" Text="Page 2">
                                    </dx:NavBarItem>
                                    <dx:NavBarItem NavigateUrl="SamplePages/Page3.aspx" Text="Page 3">
                                    </dx:NavBarItem>
                                </Items>
                            </dx:NavBarGroup>
                        </Groups>
                    </dx:ASPxNavBar>
                </dx:SplitterContentControl>
            </ContentCollection>
        </dx:SplitterPane>
        <dx:SplitterPane>
            <ContentCollection>
                <dx:SplitterContentControl runat="server">
                    <div class="exampleContent">Right container</div>
                </dx:SplitterContentControl>
            </ContentCollection>
        </dx:SplitterPane>
    </Panes>
</dx:ASPxSplitter>

using DevExpress.Web;
...
protected void Page_Load(object sender, EventArgs e) {
    ASPxSplitter splitter = new ASPxSplitter();
    splitter.ID = "splitter";

    ASPxNavBar navBar = new ASPxNavBar();
    navBar.ID = "navBar";
    navBar.AllowSelectItem = true;
    navBar.Target = "contentUrlPane";
    NavBarGroup navBarGroup = new NavBarGroup("Sample");
    navBarGroup.Items.AddRange(new List<NavBarItem>() {
        new NavBarItem { Text = "Page 1", NavigateUrl = "SamplePages/Page1.aspx"},
        new NavBarItem { Text = "Page 2", NavigateUrl = "SamplePages/Page2.aspx", Selected = true},
        new NavBarItem { Text = "Page 3", NavigateUrl = "SamplePages/Page3.aspx"},
    });
    navBar.Groups.Add(navBarGroup);

    SplitterPane pane1 = new SplitterPane();
    pane1.Controls.Add(navBar);
    splitter.Panes.Add(pane1);

    SplitterPane pane2 = new SplitterPane();
    pane2.Controls.Add(new LiteralControl("Right Container"));
    splitter.Panes.Add(pane2);

    Page.Form.Controls.Add(splitter);
}

Imports DevExpress.Web
...
Protected Sub Page_Load(ByVal sender As Object, ByVal e As EventArgs)
    Dim splitter As ASPxSplitter = New ASPxSplitter()
    splitter.ID = "splitter"
    Dim navBar As ASPxNavBar = New ASPxNavBar()
    navBar.ID = "navBar"
    navBar.AllowSelectItem = True
    navBar.Target = "contentUrlPane"
    Dim navBarGroup As NavBarGroup = New NavBarGroup("Sample")
    navBarGroup.Items.AddRange(New List(Of NavBarItem)() From {
        New NavBarItem With {
            .Text = "Page 1",
            .NavigateUrl = "SamplePages/Page1.aspx"
        },
        New NavBarItem With {
            .Text = "Page 2",
            .NavigateUrl = "SamplePages/Page2.aspx",
            .Selected = True
        },
        New NavBarItem With {
            .Text = "Page 3",
            .NavigateUrl = "SamplePages/Page3.aspx"
        }
    })
    navBar.Groups.Add(navBarGroup)
    Dim pane1 As SplitterPane = New SplitterPane()
    pane1.Controls.Add(navBar)
    splitter.Panes.Add(pane1)
    Dim pane2 As SplitterPane = New SplitterPane()
    pane2.Controls.Add(New LiteralControl("Right Container"))
    splitter.Panes.Add(pane2)
    Page.Form.Controls.Add(splitter)
End Sub