获取在document.ready中设置的隐藏字段的值，该值位于asp.net代码后面

Question

I need to access a hidden fields value in code behind, normally this is easy but this variable is being set during jQuery's document.ready event and I need to access it when the page loads... so far I have tried Page_Load , Page_LoadComplete , Init and Prerender with no luck. Is this just an impossible task?

Thanks!

Answer 1

Yes that is impossible.

(At least with known technology at this point. You would need a time machine to get that data.)

All the code on the server runs to create the page to the browser. when the server code is complete, the page is sent to the browser and the browser parses the page. When the entire page is parsed, the ready event happens.

So, all server code runs before the page is sent to the browser, and all Javascript code runs after the page is sent to the browser.

(It's technically possible to have Javascript start in the browser before the server code completes, but that means that you need to turn buffering off for the response on the server and handle the response completely by yourself (ie not Webforms or MVC), and the Javascript needs to run when the page starts loading, not in the ready event. Also, you need another page on the server that the Javascript can request to send data back to the server, and that page has to run sessionless so that the web server can handle it in parallel with the current page. Also, you need to set up some static class on the server where the data can be stored, so that the current page can pick it up when it arrives, and you have to create some kind of identifier for the request that the Javascript can send back to identify which request should get the data, as the page used to send the data is sessionless. So, even if it possible to do something similar to what you want, it's way too complicated to be practic al.)

Answer 2

So the poster above is correct, but there are lots of ways to do what you want. For example, submit a post back right after changing the value. Like below (there are many other alternatives to this as well).

public partial class WebForm1 : System.Web.UI.Page
    {
        protected void Page_Load(object sender, EventArgs e)
        {
            var test = HiddenField1.Value;

            if (test != "")
                HiddenField1.Value = "test finished";
        }
    }

<form id="form1" runat="server">

        <asp:HiddenField ID="HiddenField1" runat="server" />

        <script type="text/javascript">
            $(document).ready(function () {


                if ($('#HiddenField1').val() !== 'test finished') {
                    $('#HiddenField1').val('test');
                    $("#form1").submit();
                }

            });
        </script>

    </form>