When you use regular ASP.NET page postbacks, an error message is
displayed on the page whenever an exception is thrown on the server. When
you use asynchronous postbacks and UpdatePanel
s, the error message isn't displayed
on the full page but is instead displayed in a JavaScript alert box, as
shown in Figure 17.
The error message that gets displayed client-side in case an
exception is thrown can be modified from the server by modifying the
AsyncPostBackErrorMessage
property on
the ScriptManager
control. This is best
done from the AsyncPostBackError
event
of the ScriptManager
control. Here's
how you can add a handler for the error event:
<asp:ScriptManager runat="server" ID="SM1" OnAsyncPostBackError="AsyncError" />
And here's an example of an error handler that modifies the message that will get displayed on the client when an exception is thrown from the server:
protected void AsyncError(object sender, AsyncPostBackErrorEventArgs e) { ScriptManager.GetCurrent(this).AsyncPostBackErrorMessage = "Something terribly wrong happened: " + e.Exception.Message; }