ASPxClientCallbackPanel.BeginCallback Event

Occurs when a callback for server-side processing is initiated.

Declaration

BeginCallback: ASPxClientEvent<ASPxClientBeginCallbackEventHandler<ASPxClientCallbackPanel>>

Event Data

The BeginCallback event handler receives an argument of the ASPxClientBeginCallbackEventArgs type. The following properties provide information specific to this event.

Property Description
command Gets a command name that identifies which client action forced a callback to occur.

Remarks

The BeginCallback and ASPxClientCallbackPanel.EndCallback events can be used to perform specific client-side actions (for example, to display and hide an explanatory text or picture) while a callback is being processed on the server side.

Examples

The ASPxCallbackPanel control provides a built-in loading panel, however you can implement a custom one. For this purpose, the default panel is hidden by setting the Enabled property to false. The custom panel is implemented using the ASPxLoadingPanel control. The callback panel's BeginCallback and EndCallback client-side events are used to show and hide the loading panel respectively. Additionally, this example demonstrates how to add, modify, and hide controls in the ASPxCallbackPanel control in the Callback event handler.

<style>
    .sendCommentBlock {
        margin: 20px 0;
    }

    .comment {
        border-bottom: 1px dashed #888888;
    }
</style>
<script>
    function SendCommentCallback(s, e) {
        CallbackPanel.PerformCallback();
    };

    function OnBeginCallback(s, e) {
        LoadingPanel.Show();
    };

    function OnEndCallback(s, e) {
        LoadingPanel.Hide();
    };
</script>
<dx:ASPxButton ID="Button" runat="server" Text="Post Comment" AutoPostBack="false">
    <ClientSideEvents Click="SendCommentCallback" />
</dx:ASPxButton> 
<br />
<br />
<dx:ASPxTextBox ID="TextBox" runat="server" Width="170px"></dx:ASPxTextBox>
...
<dx:ASPxCallbackPanel ID="CallbackPanel" ClientInstanceName="CallbackPanel" 
    runat="server"
    CssClass="pnl"
    Width="300px"
    OnCallback="CallbackPanel_Callback"
    OnInit="CallbackPanel_Init">
    <SettingsLoadingPanel Enabled="false" />
    <ClientSideEvents BeginCallback="OnBeginCallback" EndCallback="OnEndCallback" />
    <PanelCollection>
        <dx:PanelContent>
            <dx:ASPxLabel ID="CountLabel" runat="server" Text="Comments Count : "></dx:ASPxLabel>
            <br />
            <br />
            <dx:ASPxLabel ID="NoCommentsLabel" runat="server" Text="No Comments" ForeColor="Gray"></dx:ASPxLabel>
        </dx:PanelContent>
    </PanelCollection>
</dx:ASPxCallbackPanel>
...
<dx:ASPxLoadingPanel ID="LoadingPanel" ClientInstanceName="LoadingPanel"
    runat="server"
    Modal="true"
    HorizontalAlign="Center"
    VerticalAlign="Middle">
    <Image Url="Images/load.gif" Height="50px" Width="50px"></Image>
</dx:ASPxLoadingPanel>
See Also