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Load Content Via Callback

You can use the built-in OnCallbackUpdate event of the RadNotification to load its content from the server via a callback. It is especially useful in combination with the LoadContentOn property set to EveryShow. The key advantage of using a callback is that the server Page does not go through its whole lifecycle, but only a small part of it. The client state is not updated, and it is not sent back to the client-side.

tip

You can use this callback to set the notification's Value property, because it will be passed to the client. You can use it, for example, as a flag or some small piece of necessary data in your application's logic.

The event passes a RadNotificationEventArgs to the handler which contains the Value property of the RadNotification that initiated it.

In the example below the server time is populated in the notification by using its Text property.

<telerik:RadNotification RenderMode="Lightweight" runat="server" ID="RadNotification1" ShowInterval="5000"
        AutoCloseDelay="2000" Position="BottomRight" Width="250px" Height="150px"
        LoadContentOn="EveryShow" OnCallbackUpdate="OnCallbackUpdate">
</telerik:RadNotification>
protected void OnCallbackUpdate(object sender, RadNotificationEventArgs e)
{
    DateTime beBack = DateTime.Now.AddDays(7);
    RadNotification1.Text = "Hi there! I am currently out of the office. I will be back on "
        + beBack.ToShortDateString();
}
 Protected Sub RadNotification1_CallbackUpdate(sender As Object, e As Telerik.Web.UI.RadNotificationEventArgs) Handles RadNotification1.CallbackUpdate
     Dim beBack As DateTime
     beBack = DateTime.Now.AddDays(7)
     RadNotification1.Text = "Hi there! I am currently out of the office. I will be back on "
          + beBack.ToShortDateString()
 End Sub