您可以使用Descendants，然后使用First或Single-当前，您正在询问***元素它的正下方有一个SendDataResult元素，而实际上没有.此外，您没有使用正确的名称空间.这应该解决它:

You can use Descendants followed by First or Single - currently you're asking the top level element whether it's got a SendDataResult element directly beneath it, which it hasn't. Additionally, you're not using the right namespace. This should fix it:

XNamespace stuff = "http://stuff.com/stuff";
string data = responseXml.Descendants(stuff + "SendDataResult")
                         .Single()
                         .Value;

或者，直接导航:

XNamespace stuff = "http://stuff.com/stuff";
XNamespace soap = "http://www.w3.org/2003/05/soap-envelope";
string data = responseXml.Element(soap + "Body")
                         .Element(stuff + "SendDataResult")
                         .Value;