linq to xml-分析datetime时检查空元素

var accountSettings =
  from settings in templateXML.Descendants("Account")
  select new Account {
    AccountExpirationDate = 
      string.IsNullOrEmpty((string)settings.Element("AccountExpirationDate")) 
            ? (DateTime?)null
            : DateTime.Parse(settings.Element("AccountExpirationDate").Value) 
  };

您只需使用:

from settings in templateXML.Descendants("Account")
let el = settings.Element("AccountExpirationDate")
let el2 = (el == null || string.IsNullOrEmpty(el.Value)) ? null : el
select new Account {
    AccountExpirationDate = (DateTime?)el2
};

有一个转换运算符使用标准的XML日期时间格式实现了这种魔力,如果元素不存在,它将返回空值(注意,我没有阅读 .Value )

尝试:

var accountSettings = from settings in templateXML.Descendants("Account")
                  where settings.Element("AccountExpriationDate") != null
                  && !String.IsNullOrEmpty(settings.Element("AccountExpriationDate").Value)
                  select new Account 
                  {
                      AccountExpirationDate = DateTime.Parse(settings.Element("AccountExpirationDate").Value)
                  };

对于更可读的语法,如果您需要多次这样的检查,可以使用扩展方法:

public static DateTime? ToDateTime(this Element e)
    {
        if (e == null)
            return null;

        if (string.IsNullOrEmpty(e.Value))
            return null;
        else
            return DateTime.Parse(e.Value);
    }