How to get javascript value in c# code behind

Question

I tried a hidden field control, but it doesn't return the javascript value to the code behind in c#. When I execute the code below, it always returns 0.

How do I get the distance value from javascript to c#?

<script type="text/javascript" src="http://maps.google.com/maps/api/js?sensor=false"></script>

<script type="text/javascript">
    function GetDistance()
    {
        var origin = document.getElementById("orig").value,
            destination = document.getElementById("dest").value,
            service = new google.maps.DistanceMatrixService();
        service.getDistanceMatrix(
            {
                origins: [origin],
                destinations: [destination],
                travelMode: google.maps.TravelMode.DRIVING,
                avoidHighways: false,
                avoidTolls: false
            },
            callback
        );

        function callback(response, status) {
            alert('hello2');
            var orig = document.getElementById("orig"),
                dest = document.getElementById("dest"),
                dist = document.getElementById("dist");
            if (status == "OK") {
                orig.value = response.originAddresses[0];
                dest.value = response.destinationAddresses[0];
                dist.value = response.rows[0].elements[0].distance.text;
                document.getElementById('<%=hdnResultValue.ClientID%>').value = dist.value;

            } else {
                alert("Error: " + status);
            }
        }
    }
</script>


<form id="frm1"  runat="server" method="post">
    <br>
    Basic example for using the Distance Matrix.<br><br>
    Origin: <input id="orig" type="text" style="width:35em"><br><br>
    Destination: <input id="dest" type="text" style="width:35em"><br><br>
    Distance: <input id="dist" type="text" style="width:35em">
    <asp:Button ID="btnSubmit" runat="server" Text ="Submit Application" OnClientClick="GetDistance();" OnClick="btnSubmit_Click" />
    <asp:Label ID="lblDistance" runat="server" Text=" " />
    <asp:HiddenField ID="hdnResultValue" Value="0" runat="server" />
    </form>
 protected void btnSubmit_Click(object sender, EventArgs e)
        {
            lblDistance.Text = hdnResultValue.Value;
            lblDistance.Text += "Calculated Successfully";
        }

Answer 1

See Distance Matrix Service Specification .

The method return only one DistanceMatrixResponse object. If you want status of your request, you have to parse received JSON element as presented on linked page : rows[index].elements.status.

{
  "origin_addresses": [ "Greenwich, Greater London, UK", "13 Great Carleton Square, Edinburgh, City of Edinburgh EH16 4, UK" ],
  "destination_addresses": [ "Stockholm County, Sweden", "Dlouhá 609/2, 110 00 Praha-Staré Město, Česká republika" ],
  "rows": [ {
    "elements": [ {
      "status": "OK",
      "duration": {
        "value": 70778,
        "text": "19 hours 40 mins"
      },
      "distance": {
        "value": 1887508,
        "text": "1173 mi"
      }
    }, {
      "status": "OK",
      "duration": {
        "value": 44476,
        "text": "12 hours 21 mins"
      },
      "distance": {
        "value": 1262780,
        "text": "785 mi"
      }
    } ]
  }, {
    "elements": [ {
      "status": "OK",
      "duration": {
        "value": 96000,
        "text": "1 day 3 hours"
      },
      "distance": {
        "value": 2566737,
        "text": "1595 mi"
      }
    }, {
      "status": "OK",
      "duration": {
        "value": 69698,
        "text": "19 hours 22 mins"
      },
      "distance": {
        "value": 1942009,
        "text": "1207 mi"
      }
    } ]
  } ]
}