如何在代码隐藏中检查请求是否是ajax - ASP.NET Webforms

<asp:ScriptManager ID="ScriptManager1" runat="server" EnablePartialRendering="true"></asp:ScriptManager>

<script runat="server">
    protected void Page_Load(object sender, EventArgs e)
    {
        if (ScriptManager1.IsInAsyncPostBack)
        {
            // Ajax请求
        }
        else
        {
            // 非Ajax请求
        }
    }
</script>

<script type="text/javascript">
    var prm = Sys.WebForms.PageRequestManager.getInstance();

    prm.add_beginRequest(beginRequestHandler);

    function beginRequestHandler(sender, args) {
        if (args.get_postBackSettings().get_async()) {
            // Ajax请求
        }
        else {
            // 非Ajax请求
        }
    }
</script>