access javascript variable in asp.net codebehind

Question

I need to store the geolocation(lat,long) when on page_load to a db table.

For which I use this script.

<body onload="getLocation()">

    <p>Click the button to get your coordinates.</p>

            <%--<button onclick="getLocation()">Try It</button>--%>

            <p id="demo"></p>


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

            <p>
                <asp:HiddenField ID="hdnLocation" ClientIDMode="Static" runat="server" />
 <asp:Label ID="lblloc" runat="server"></asp:Label>
                <asp:TextBox ID="txtloc" runat="server"></asp:TextBox>
                <asp:Button ID="btnLoc" text="submit" runat="server" OnClick="btnLoc_Click" />

            </p>
        </div>
    </form>

        <script>
            var x = document.getElementById("demo");

            function getLocation() {
                if (navigator.geolocation) {
                    navigator.geolocation.getCurrentPosition(showPosition);
                } else {
                    x.innerHTML = "Geolocation is not supported by this browser.";
                }
            }

            function showPosition(position) {
                x.innerHTML = "Latitude: " + position.coords.latitude +
                "<br>Longitude: " + position.coords.longitude;
                $("[id*=hdnLocation]").val(position.coords.latitude + ' ' + position.coords.longitude);
            //    $("[id*=btnLoc]").trigger("click");
            }
            </script>

</body>
</html>

here is my code behind public partial class getLocation : System.Web.UI.Page

{ protected void Page_Load(object sender, EventArgs e) {

    lblloc.Visible = true;

    lblloc.Text = hdnLocation.Value;
    txtloc.Text = hdnLocation.Value;

}

when I run the page I get values in hidden field when I inspect in browser.

But can't access the hidden field values in code behind. Response.Write comes blank and lblloc.text comes null.

What could be the problem.

Seano666 · Accepted Answer · 2017-04-18 20:03:44Z

0

In order for your current jQuery selector to work, your HTML element needs to have the ClientIDMode property set to "Static".

With server elements in .NET, the server id and the client id are two very different things. This ensures they are the same for this element.

<asp:HiddenField ID="hdnLocation" runat="server" ClientIDMode="Static" />

answered Apr 18, 2017 at 20:03

Seano666

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Mi6u3l · Accepted Answer · 2017-04-18 22:13:08Z

0

This should work:

HTML

<script type="text/javascript">
function abc()
{
  var str="value";
  document.getElementById("Hidden1").value=str;
}


</script>
<body>
    <form id="form1" runat="server">
    <div>
        <input id="Hidden1" type="hidden" runat="server" />
        <asp:Button ID="Button1" runat="server" OnClientClick="abc()"  Text="Button"
            onclick="Button1_Click" />
    </div>
    </form>
</body>

Code behind

Response.Write(Hidden1.Value);

answered Apr 18, 2017 at 22:13

Mi6u3l

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1 Comment

Mashhoor Gulati Over a year ago

document.getElementById("Hidden1").value=str; .value is not identified even it doesn't show up in intellisense. Instead .nodevalue and .valueof comes.

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