问题描述

我面临的情况是使用 Linq 将 XML 文档解析为对象.在解析过程中，我正在检查以确保元素不为空，然后再继续解析它们的值.有没有办法简化这句话?

The situation I am faced with is parsing an XML document into an object using Linq. During the parse I am checking to make sure Elements are not null before proceeding to parse out their values. Is there anyway to simplify this statement?

  var variable = (from x in xdoc.Descendants("Root")
                 select new AccountingResponse
                 {      
                 NetCharge = x.Element("Charges") != null && x.Element("Charges").Element("NetCharge") != null ? x.Element("Charges").Element("NetCharge").Value : "0",
                 TotalCharge = x.Element("Charges") != null && x.Element("Charges").Element("TotalCharge") != null ? x.Element("Charges").Element("TotalCharge").Value : "0"
                 }).SingleOrDefault();

总而言之，我不想继续检查每行是否存在节点.我知道我可以在解析之前测试该节点是否存在，但可能还有其他数据需要解析以创建 AccountingResponse，我想避免一次只解析一部分 XML 的 if 语句.

To summarize, I do not want to continue to check if the nodes exist on each line. I know I can test to see if the node exists prior to the parsing, but there may be other data that needs parsed to create the AccountingResponse and I want to avoid if statements that only parse a portion of the XML out at a time.

或者也许我做错了，有更好的方法！

Or perhaps I'm doing this completely wrong and there's a better way!

推荐答案

一个简单的选择是使用 Elements 而不是 Element - 这将返回一个零长度的序列如果元素不存在.所以你可以使用:

One simple option is to use Elements rather than Element - that will return a zero-length sequence if the element isn't present. So you can use:

from x in xdoc.Descendants("Root")
select new AccountingResponse
{      
    NetCharge = x.Elements("Charges")
                 .Elements("NetCharge")
                 .Select(y => (int) y)
                 .FirstOrDefault(),
    TotalCharge = x.Elements("Charges")
                   .Elements("TotalCharge")
                   .Select(y => (int) y)
                   .FirstOrDefault(),
}).SingleOrDefault();

(请注意，您的原始代码不会编译，因为 Value 是一个字符串，而 0 是一个 int...)

(Note that your original code wouldn't compile, as Value is a string whereas 0 is an int...)

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