c# - 错误 : A query body must end with a select clause or a group clause

Question

我有这样一个 xml:

<countries>
    <country ID="MX">
        <idea ID="Valor1">nota1</idea>
        <idea ID="Valor2">nota2</idea>
        <idea ID="Valor3">nota3</idea>
        <idea ID="Valor4">nota4</idea>
    </country>
    <country ID="US">
        <idea ID="Valor1">nota1</idea>
        <idea ID="Valor2">nota2</idea>
        <idea ID="Valor3">nota3</idea>
        <idea ID="Valor4">nota4</idea>
    </country>
</countries>

如何使用 LINQ to XML 获取特定类型的列表？我试过这样的事情:

我创建了一个类:

public class Ideas
{
    public string Country { get; set; }

    public List<ListItem> ListIdeas { get; set; }
}

然后我用这个类做一个列表:

XDocument xdoc = XDocument.Load(this.Server.MapPath("~/config/ideas.xml"));

var cat = from p in xdoc.Descendants("countries")
                        .Elements("country")
                        .Select(m => new Ideas 
                            {
                                Country = m.Attribute("ID").Value, 
                                ListIdeas = m.Elements("idea")
                                             .Select(c => 
                                                 new ListItem 
                                                 {
                                                     Text = c.Attribute("ID").Value , 
                                                     Value = c.Value
                                                 }).ToList()
                            });

但是我得到下一个错误:

A query body must end with a select clause or a group clause

The type of the expression in the select clause is incorrect. Type inference failed in the call to 'Select'.

Answer 1

您混合了查询语法和扩展方法语法。选择一个。

var r = (from c in xdoc.Element("countries")
                       .Elements("country")
         select new Country
         {
             ID = c.Attribute("ID").Value,
             Ideas = (from i in c.Elements("idea")
                      select new Idea
                      {
                          Text = i.Attribute("ID").Value, 
                          Value = i.Value
                      }).ToList()
         }).ToList();

请注意，为了更好的可读性，我重命名了您的类和属性。

---

在另一种语法中相同:

var q = xdoc.Element("countries")
            .Elements("country")
            .Select(c => new Country
                 {
                      ID = c.Attribute("ID").Value,
                      Ideas = c.Elements("idea")
                               .Select(i => new Idea
                                   {
                                       Text = i.Attribute("ID").Value, 
                                       Value = i.Value
                                   })
                               .ToList()
                 })
            .ToList();