我有以下xml。由于addr在这种情况下是空的,但大部分时间它都有像街道,城市,州这样的元素。我如何确保它存在。原因现在LINQ查询会引发错误“对象引用未设置为对象的实例”。使用LINQ选择是否存在XML元素
<author>
<time value="20120620153233"/>
<assignedAuthor>
<id/>
<addr/>
<telecom value="tel:+1-781-271-3000"/>
<assignedPerson>
<name>Auto Generated</name>
</assignedPerson>
</assignedAuthor>
</author>
tbAuthor autor =
(from c in cdafile.Root.Elements(ns + "author")
select new tbAuthor
{
streetAddressLine = (string)c.Element(ns + "assignedAuthor").Element(ns + "addr").Element(ns + "streetAddressLine").Value,
city = (string)c.Element(ns + "assignedAuthor").Element(ns + "addr").Element(ns + "city").Value,
state = (string)c.Element(ns + "assignedAuthor").Element(ns + "addr").Element(ns + "state").Value,
postalCode = (string)c.Element(ns + "assignedAuthor").Element(ns + "addr").Element(ns + "postalCode").Value,
country = "US"
}).FirstOrDefault();
你怎么在有ns变量? –