Handle and display exception error message during AJAX UpdatePanel Partial PostBack in ASP.Net

Inside the UpdatePanel endRequest handler, we can fetch the error message occured at server and prevent further bubbling of error.

HTML

<asp:ScriptManager runat="server">
</asp:ScriptManager>
<asp:UpdatePanel runat="server">
    <ContentTemplate>
        <asp:Button runat="server" Text="Convert" OnClick="ConvertToInt" />
    </ContentTemplate>
</asp:UpdatePanel>
<script type="text/javascript">
    var prm = Sys.WebForms.PageRequestManager.getInstance();
    if (prm != null) {
        prm.add_endRequest(function (sender, e) {
            if (sender._postBackSettings.panelsToUpdate != null) {
                alert(e.get_error().message);
                e.set_errorHandled(true);
            }
        });
    };
</script>

Code

protected void ConvertToInt(object sender, EventArgs e)
{
    int a = Convert.ToInt32("a");
}