Skip to main content

ASPxClientCallbackPanel.EndCallback Event

Occurs on the client side after a callback’s server-side processing has been completed.

Declaration

EndCallback: ASPxClientEvent<ASPxClientEndCallbackEventHandler<ASPxClientCallbackPanel>>

Event Data

The EndCallback event's data class is ASPxClientEndCallbackEventArgs. 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 ASPxClientCallbackPanel.BeginCallback and 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.

Example

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.

View Example

<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>
using DevExpress.Web;

public partial class _Default : System.Web.UI.Page {
    protected void CallbackPanel_Callback(object sender, DevExpress.Web.CallbackEventArgsBase e) {
        ASPxCallbackPanel panel = (ASPxCallbackPanel)sender;
        NoCommentsLabel.Visible = false;
        Thread.Sleep(3000);

        ASPxLabel comment = new ASPxLabel() {
            Text = string.Format("[{0}]\n{1}\n\n",
                DateTime.Now.ToLocalTime(),
                !string.IsNullOrEmpty(TextBox.Text) ? TextBox.Text : "Empty comment"
            ),
            CssClass = "comment"
        };

        List<ASPxLabel> comments = (List<ASPxLabel>)Session["comments"] ?? new List<ASPxLabel>();

        comments.Add(comment);
        panel.Controls.Add(comment);
        Session["comments"] = comments;

        CountLabel.Text = "Comments Count : " + comments.Count;
    }

    protected void CallbackPanel_Init(object sender, EventArgs e) {
        if(!IsPostBack && !IsCallback)
            Session.Clear();
        RecreateComments(sender);
    }

    private void RecreateComments(object sender) {
        List<ASPxLabel> comments;
        if((comments = (List<ASPxLabel>)Session["comments"]) != null) {
            CountLabel.Text = "Comments Count : " + comments.Count;
            ASPxCallbackPanel panel = (ASPxCallbackPanel)sender;
            NoCommentsLabel.Visible = false;
            foreach(ASPxLabel comment in comments) {
                panel.Controls.Add(comment);
            }
        }
    }
}
See Also