Callback Panel

The Callback Panel (ASPxCallbackPanel) is a container area that allows you to update its content using an AJAX-based callback technology. Use the ASPxPanelContainerBase.Controls property to provide access to the control's child control collection.

Use the PerformCallback(parameter) method to send a callback to the server. The control uses the Callback event to handle this callback on the server. The control also has the BeginCallback and EndCallback client-side events to process callbacks when they are sent to the server and returned to the client.

Declaratively:

<dx:ASPxCallbackPanel ID="ASPxCallbackPanel1" runat="server" Width="200px">
    <PanelCollection>
        <dx:PanelContent runat="server">
            <dx:ASPxTextBox ID="ASPxTextBox1" runat="server" Width="170px">
            </dx:ASPxTextBox>
        </dx:PanelContent>
    </PanelCollection>
</dx:ASPxCallbackPanel>

In Code:

protected void Page_Load(object sender, EventArgs e)
{
    ASPxCallbackPanel cpanel = new ASPxCallbackPanel();
    cpanel.ID = "ASPxCallbackPanel1";
    cpanel.Controls.Add(new ASPxTextBox() { ID = "ASPxTextBox1", Text = "Test" });
    form1.Controls.Add(cpanel);
}

Online Demo