阅读使用的XDocument＆放XML; LINQ - 检查是否元素为空？ [英] Reading XML using XDocument & Linq - check if element is NULL?

问题描述

我在一起使用LINQ用的XDocument读取XML文件。这是code：

I'm using LINQ together with XDocument to read a XML File. This is the code:

XDocument xml = XDocument.Load(filename);

var q = from b in xml.Descendants("product")
        select new
        {
            name = b.Element("name").Value,
            price = b.Element("price").Value,                    
            extra = b.Element("extra1").Value,
            deeplink = b.Element("deepLink").Value                   
        };

现在的问题是，在 extra1 字段并不总是present。有没有该节点的XML文件中的项目。如果出现这种情况它的崩溃与一个NullReferenceException。

Now the problem is, the extra1 field is not always present. There are items in the XML file without that node. If that happens it's crashing with a NullReferenceException.

有没有可能性，包括检查空这样我就可以从崩溃prevent呢？

Is there any possibility to include a "check if null" so I can prevent it from crashing?

推荐答案

使用（串）而不是 .value的：

var q = from b in xml.Descendants("product")
        select new
        {
            name = (string)b.Element("name"),
            price = (double?)b.Element("price"),                    
            extra = (string)b.Element("extra1"),
            deeplink = (string)b.Element("deepLink")                   
        };

这也适用于其它数据类型的，包括很多可空类型的情况下，该元素并不总是present。

This also works with other datatypes, including many nullable types in case the element is not always present.

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