为什么我的方法总是返回null？

Question

<Response xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" 
          xmlns:xsd="http://www.w3.org/2001/XMLSchema" 
          xmlns="http://schemas.microsoft.com/search/local/ws/rest/v1">
  <Copyright>Copyright &#xA9; 2011 Microsoft and its suppliers. All rights
   reserved. This API cannot be accessed and the content and any results
   may not be used, reproduced or transmitted in any manner without express
   written permission from Microsoft Corporation.</Copyright>
  <BrandLogoUri>[http://dev.virtualearth.net/Branding/logo_powered_by.png]</BrandLogoUri>
  <StatusCode>200</StatusCode>
  <StatusDescription>OK</StatusDescription>
  <AuthenticationResultCode>ValidCredentials</AuthenticationResultCode>
  <TraceId>50230e70257e4ed5a5002a3d4a625c83|LTSM001156|02.00.159.1700|LTSMSNVM001471, LTSMSNVM001477</TraceId>
  <ResourceSets>
    <ResourceSet>
      <EstimatedTotal>1</EstimatedTotal>
      <Resources>
        <Location>
          <Name>1 Microsoft Way, Redmond, WA 98052</Name>
          <Point>
            <Latitude>47.640568390488625</Latitude>
            <Longitude>-122.1293731033802</Longitude>
          </Point>
          <BoundingBox>
            <SouthLatitude>47.636705672917948</SouthLatitude>
            <WestLongitude>-122.137016420622</WestLongitude>
            <NorthLatitude>47.6444311080593</NorthLatitude>
            <EastLongitude>-122.1217297861384</EastLongitude>
          </BoundingBox>
          <EntityType>Address</EntityType>
          <Address>
            <AddressLine>1 Microsoft Way</AddressLine>
            <AdminDistrict>WA</AdminDistrict>
            <AdminDistrict2>King Co.</AdminDistrict2>
            <CountryRegion>United States</CountryRegion>
            <FormattedAddress>1 Microsoft Way, Redmond, WA 98052</FormattedAddress>
            <Locality>Redmond</Locality>
            <PostalCode>98052</PostalCode>
          </Address>
          <Confidence>Medium</Confidence>
        </Location>
      </Resources>
    </ResourceSet>
  </ResourceSets>
</Response>

My query formerly looked like:

private void getData()
{
    // Api letőltése
    WebClient webClient = new WebClient();

    string url = "http://dev.virtualearth.net/REST/v1/Locations/" 
                 + _location + "?o=xml&key=App-asdf";

    webClient.DownloadStringCompleted += (s, e) =>
        {
            if (e.Error != null)
                return;

            XDocument xmlLocation = XDocument.Parse(e.Result);

            var ns = XNamespace.Get("http://schemas.microsoft.com/search/local/ws/rest/v1");
            var locality = from q in xmlLocation.Descendants(ns + "Address")
                           select (string)q.Element(ns + "Locality").Value;
        };

    webClient.DownloadStringAsync(new Uri(url));
}

Why does it always return null ?

I want to query the locality but my variable always contains null . I recently wrote a similar program code which worked but now have a namespace and don't understand what the problem would be.

Answer 1

I just ran your query against the listed XML and it produces "Redmond".

So: Break it down. You have a communication or threading problem.

    if (e.Error != null)
                return;

Is a good way to sweep the problem under the rug.

Answer 2

var locality = xmlLocation.Descendants(ns + "Locality").Select( x => x.Value);