linq to xml and namespaces

I'm always so excited to get a cha开发者_如何学JAVAnce to use linq to xml and then I run into the same PITA issue with namespaces. Not sure what is wrong with me but I can never quite grok what is going on. Basically I just need to get the value of the responseCode element and so far I have had no luck :(

<?xml version="1.0" encoding="IBM437"?>
<soapenv:Envelope xmlns:soapenv="http://schemas.xmlsoap.org/soap/envelope/">
 <soapenv:Body>
   <ns1:ActionResponse xmlns:ns1="http://cbsv.ssa.gov/ws/datatype">
     <ns1:responseCode>0000</ns1:responseCode>
     <ns1:responseDescription>Successful</ns1:responseDescription>
   </ns1:ActionResponse>
 </soapenv:Body>
</soapenv:Envelope>

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Namespaces in LINQ to XML are really elegantly handled, IMO. Here's an example:

XNamespace ns1 = "http://cbsv.ssa.gov/ws/datatype";
XDocument doc = XDocument.Load(...);
string code = doc.Descendants(ns1 + "responseCode")
                 .Select(x => (string) x)
                 .First();

If you want to work down from the top, using both of the namespaces involved, that's okay too:

XNamespace ns1 = "http://cbsv.ssa.gov/ws/datatype";
XNamespace soapenv = "http://schemas.xmlsoap.org/soap/envelope/";
XDocument doc = XDocument.Load(...);
string code = (string) doc.RootElement
                          .Element(soapenv + "Body")
                          .Element(ns1 + "ActionResponse")
                          .Element(ns1 + "responseCode");

Just to be clear, there's nothing forcing you to use the same variable name as the namespace prefix in the XML - I've just done so for clarity.

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With XML like this:

<esri:DataElement xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:xs="http://www.w3.org/2001/XMLSchema" xmlns:esri="http://www.esri.com/schemas/ArcGIS/10.0" xsi:type="esri:DEFeatureClass">
  <CatalogPath>\counties</CatalogPath>
  <Name>counties</Name>

…

</esri:DataElement>

I was using queries like:

tableInfo.TableName = (from element in xDoc.Descendants("Name")
                                                   select Convert.ToString(element.Value)).FirstOrDefault();

But if you define the namespace in your code, then you can get more specific, faster:

XNamespace esri = "http://www.esri.com/schemas/ArcGIS/10.0";

tableInfo.TableName = xDoc.Element(esri + "DataElement").Element("Name").Value;

You can think of declaring the namespace as taking the place of “esri:” in strings. (There’s no way to use a colon in a query either). Also, in a file like this, I was finding multiple occurrences of tags so it’s important to get the right ones (or at least just one set). Before, I was ending up with redundant info for fields, which would mess up creating a SQL Server table. Now I can define which item I want related to the document root.