Linq to xml .net3.5 查询失败

Question

xml： <?xml version="1.0" encoding="utf-8" ?><EntityDescriptor xmlns="urn:oasis:names:tc:SAML:2.0:metadata"   xmlns:saml="urn:oasis:names:tc:SAML:2.0:assertion" xmlns:ds="http://www.w3.org/2000/09/xmldsig#" entityID="http://10.162.1.220:8082/bspcore">   <IDPSSODescriptor WantAuthnRequestsSigned="true" protocolSupportEnumeration="urn:oasis:names:tc:SAML:2.0:protocol">    <SingleSignOnService isDefault="true" index="0"   Binding="urn:oasis:names:tc:SAML:2.0:bindings:HTTP-POST"   Location="http://10.162.1.220:8082/bspcore/SAML2/POST/SSO" />    <SingleSignOnServiceBinding="urn:oasis:names:tc:SAML:2.0:bindings:HTTP-Redirect"Location="http://10.162.1.220:8082/bspcore/SAML2/REDIRECT/SSO" />    <ArtifactResolutionServiceBinding="urn:oasis:names:tc:SAML:2.0:bindings:SOAP" Location="http://10.162.1.220:8082/bspcore/SAML2/Artifact" />    <SingleLogoutServiceBinding="urn:oasis:names:tc:SAML:2.0:bindings:SOAP" Location="http://10.162.1.220:8082/bspcore/SAML2/SLO/SOAP" />    <SingleLogoutServiceBinding="urn:oasis:names:tc:SAML:2.0:bindings:HTTP-Redirect"Location="http://10.162.1.220:8082/bspcore/SAML2/SLO/REDIRECT" ResponseLocation="http://10.162.1.220:8082/bspcore/SAML2/SLO/Response" />    <NameIDFormat>      urn:oasis:names:tc:SAML:1.1:nameid-format:X509SubjectName    </NameIDFormat>    <NameIDFormat>      urn:oasis:names:tc:SAML:2.0:nameid-format:persistent    </NameIDFormat>    <NameIDFormat>      urn:oasis:names:tc:SAML:2.0:nameid-format:transient    </NameIDFormat>  </IDPSSODescriptor></EntityDescriptor>   代码：   XElement idpdoc = XElement.Load(new StreamReader("E:\\IDP.xml"));             var test = idpdoc.Descendants("NameIDFormat");var NameIdFormats = (from ni in idpdoc.Descendants() where ni.Name=="NameIDFormat" select ni.Value).ToList<String>();   结果： test.Count()=0; NameIdFormats .Count()=0;