使用linq-xml深入查询xElement

Question

I have XML 我有XML

<Envelopes>
  <Envelope   xmlns:env="http://www.w3.org/2003/05/soap-envelope">
    <Body>
      <UpdateObjectResponse xmlns="http://www.sap.com/SBO/DIS" 
                            CommandID="UpdateObject picklist">
        <RetKey>426358</RetKey>
        <RetType>156</RetType>
      </UpdateObjectResponse>
    </Body>
  </Envelope>                
  <Envelope xmlns:env="http://www.w3.org/2003/05/soap-envelope">
    <Body>
      <UpdateObjectResponse xmlns="http://www.sap.com/SBO/DIS" 
                            CommandID="UpdateObject picklist">
        <RetKey>426358</RetKey>
        <RetType>156</RetType>
      </UpdateObjectResponse>
    </Body>
  </Envelope>
</Envelopes>

and I am trying to get value of RetKey element like so 我试图像这样获取RetKey元素的值

var query = from t in xdoc.Descendants("Envelope") select t;

foreach (XElement item in query)
{
    var k = item.Element("Body").Element("UpdateObjectResponse").Element("RetKey").Value;
}

var query and item are getting set properly, but I am getting this error within the foreach loop var query和item已正确设置，但我在foreach循环中收到此错误

"Object reference not set to an instance of an object." “你调用的对象是空的。”

Answer 1

I cannot see anything obvious that's wrong with your code. 我看不到任何明显的代码错误。

I'll assume you're using VS? 我假设您使用的是VS？ Try running the following code with a break point in each line of the foreach and chech the locals at each step, to see which of the .Element(..) queries might be the problem. 尝试在foreach的每一行中运行带有断点的以下代码，并在每一步检查本地变量，以查看可能是哪个.Element（..）查询。 Check each of the variables in in the locals view at each step, to see if something unexpected appears in one of the XElements. 在每个步骤中，请在locals视图中检查每个变量，以查看是否有意外情况出现在XElement之一中。

var query = from t in xdoc.Descendants("Envelope") select t;
foreach (XElement item in query)
{
    var j = item;
    var k = item.Element("Body");
    var l = k.Element("UpdateObjectResponse");
    var m = l.Element("RetKey");
    var n = m.Value;
}

Either you will see which of the variables jklmn is different than expected, or the code will break with a more informative exception. 您可能会看到jklmn中的哪个变量与预期的不同，或者代码将以更多信息性异常中断。

Note: at least in VS2015, there's a little magnifying glass in the locals view, which lets you nicely view XMLs (in case you didn't know). 注意：至少在VS2015中，locals视图中有一个放大镜，可让您很好地查看XML（以防万一）。

Edit : I was not aware of the differences between XElement.Descendants and XElement.Elements and I am still unclear on how to do this properly with the cascaded namespaces. 编辑：我不知道XElement.Descendants和XElement.Elements之间的区别，我仍然不清楚如何正确地使用级联名称空间。 See Without or only root namespace . 请参阅不使用或仅使用根名称空间。 See Strip namespaces from Elements in case the namespace isn't fixed. 如果名称空间不固定，请参见从Elements中剥离名称空间。

I think that this might be the solution, though. 我认为这可能是解决方案。 If I get it correctly, you can just write 如果我没弄错，你可以写

XNamespace ns = "http://www.sap.com/SBO/DIS";
var klist = from t in xdoc.Descendants(ns + "RetKey") select t.Value;

to get a list of the RetKey values in that xml. 获取该xml中RetKey值的列表。 Maybe also try xdoc.Root.Descendants to avoid the first namespace. 也许还尝试使用xdoc.Root.Descendants来避免第一个名称空间。

使用linq-xml深入查询xElement

问题描述

1 个解决方案

解决方案1
1 2015-09-17 13:47:10

使用linq-xml深入查询xElement

问题描述

1 个解决方案

解决方案1 1 2015-09-17 13:47:10

解决方案1
1 2015-09-17 13:47:10