老赵点滴

<jeffz:SwitchPartManager ID="SwitchPartManager1" runat="server"
    PlaceHolderUpdatePanelID="UpdatePanel1" />

<asp:Button ID="ButtonA" runat="server" Text="ControlA" OnClick="ButtonA_Click" />
<asp:Button ID="ButtonB" runat="server" Text="ControlB" OnClick="ButtonB_Click" />

<hr />

<asp:UpdatePanel ID="UpdatePanel1" runat="server"></asp:UpdatePanel>

protected void Page_Load(object sender, EventArgs e)
{
    ScriptManager sm = ScriptManager.GetCurrent(this);
    sm.RegisterAsyncPostBackControl(this.ButtonA);
    sm.RegisterAsyncPostBackControl(this.ButtonB);
}

protected void ButtonA_Click(object sender, EventArgs e)
{
    SwitchPartManager.GetCurrent(this).SwitchTo("ControlA");
}

protected void ButtonB_Click(object sender, EventArgs e)
{
    SwitchPartManager.GetCurrent(this).SwitchTo("ControlB");
}

This is Control A. 
<asp:LinkButton ID="LinkButton1" runat="server"
    OnClick="LinkButton1_Click">Switch To Control B</asp:LinkButton>

protected void LinkButton1_Click(object sender, EventArgs e)
{
    SwitchPartManager.GetCurrent(this.Page).SwitchTo("ControlB");
}

This is Control B
<br />
<asp:UpdatePanel ID="UpdatePanel1" runat="server">
    <ContentTemplate>
        <%= DateTime.Now %>
        <asp:Button ID="Button1" runat="server" Text="Refresh Time" />
    </ContentTemplate>
</asp:UpdatePanel>

[PersistChildren(false)]
[ParseChildren(true)]
[NonVisualControl]
public class SwitchPartManager : Control
{
    private const string HiddenElementName = "__PartType__";

    private bool initialized = false;

    private string partTypeToSave = null;

    public static SwitchPartManager GetCurrent(Page page)
    {
        return page.Items[typeof(SwitchPartManager)] as SwitchPartManager;
    }

    protected override void OnInit(EventArgs e)
    {
        base.OnInit(e);

        if (this.Page.Items.Contains(typeof(SwitchPartManager)))
        {
            throw new InvalidOperationException("One SwitchPartManager per page.");
        }

        this.Page.Items[typeof(SwitchPartManager)] = this;

        this.Page.InitComplete += new EventHandler(Page_InitComplete);
        this.Page.PreRenderComplete += new EventHandler(Page_PreRenderComplete);
    }

    private void Page_InitComplete(object sender, EventArgs e)
    {
        this.initialized = true;

        string partType = this.Page.Request.Params[SwitchPartManager.HiddenElementName];
        if (partType != null)
        {
            this.SwitchTo(partType);
        }
    }

    private void Page_PreRenderComplete(object sender, EventArgs e)
    {
        if (!String.IsNullOrEmpty(this.partTypeToSave))
        {
            ScriptManager.RegisterHiddenField(
                this.Page, SwitchPartManager.HiddenElementName, this.partTypeToSave);
        }
    }

    // 得到作为容器的UpdatePanel
    private UpdatePanel PlaceHolderUpdatePanel
    {
        get
        {
            // ...
        }
    }

    public void SwitchTo(string partType)
    {
        Control container = this.PlaceHolderUpdatePanel.ContentTemplateContainer;
        container.Controls.Clear();

        Control control = this.Page.LoadControl(partType + ".ascx");
        control.ID = "JustToPreserveUniqueName";
        container.Controls.Add(control);

        this.partTypeToSave = partType;
    }
}