Linq to XML，其中值为 null

Question

我的代码有一些问题，

public IQueryable<PageItems> GetPageById(Guid Id)
{
    var xml = Utility.LoadXmlFile("Pages/" + Id);

    var q = (from f in xml.Descendants("Page")
             where (Guid)f.Element("id") == Id
             select new PageItems
             {
                 Title = f.Element("Title").Value,
                 Content = f.Element("Content").Value,
                 PublishDate = f.Element("PublishDate").Value,
             }).AsQueryable();


    return q;
}

我收到此错误：

Value cannot be null.
Parameter name: element 
Line 63: where (Guid)f.Element("id") == Id

xml 文件：

<Page id="235487c9-f706-4550-831e-cc504e99d3c5">
  <Title>Test</Title>
  <Content>Test</Content>
  <PublishDate>Test</PublishDate>
  <Url>about/contact</Url>
</Page>

Answer 1

您已要求提供 id 元素，但您需要属性：

var q = (from f in xml.Descendants("Page")
         where (Guid)f.Attribute("id") == Id
         select new PageItems
         {
             Title = f.Element("Title").Value,
             Content = f.Element("Content").Value,
             PublishDate = f.Element("PublishDate").Value,
         }).AsQueryable();

将其作为 IQueryable 返回的任何原因，由方式？