Question

我有以下XML

<Group>
    <Id>2</Id>
    <GroupName>Fizzy Drinks</GroupName>
    <DateCreated>0001-01-01T00:00:00</DateCreated>
    <DateModified>0001-01-01T00:00:00</DateModified>
    <Person>
      <PersonId>78</PersonId>
      <PersonName>Francesca</PersonName>
      <PersonSurname>Andrews</PersonSurname>
      <PersonAge>59</PersonAge>
    </Person>
    <Products>
      <ProductId>2</ProductId>
      <ProductName>Oranges</ProductName>
      <CategoryId>4</CategoryId>
      <CategoryName></CategoryName>
      <SubCategoryId>7</SubCategoryId>
      <SubCategoryName>Bread</SubCategoryName>
    </Products>
    <Products>
      <ProductId>12</ProductId>
      <ProductName>Pepsi</ProductName>
      <CategoryId>4</CategoryId>
      <CategoryName></CategoryName>
      <SubCategoryId>8</SubCategoryId>
      <SubCategoryName>Dairy</SubCategoryName>
    </Products>
    <Products>
      <ProductId>14</ProductId>
      <ProductName>Multiwheat Bread</ProductName>
      <CategoryId>4</CategoryId>
      <CategoryName></CategoryName>
      <SubCategoryId>7</SubCategoryId>
      <SubCategoryName>Bread</SubCategoryName>
    </Products>
</Group>

我希望在Group对象中检索以下内容。

我有以下代码： -

            foreach (XElement xe in xdoc.Descendants("Group"))
        {
            int id = Convert.ToInt32(xe.Element("Id").Value);

            var group = from g in xdoc.Descendants("Group")
                        where (int)g.Element("Id") == id // filtering groups here
                        select new Group
                        {
                            Id = (int)g.Element("Id"),
                            GroupName = (string)g.Element("GroupName"),
                            DateCreated = (DateTime)g.Element("DateCreated"),
                            DateModified = (DateTime)g.Element("DateModified"),
                            Person = from d in g.Descendants("Person")
                                     select new Person
                                         {
                                             Id = (int)d.Element("PersonId"),
                                             Name = (string)d.Element("PersonName"),
                                             Surname = (string)d.Element("PersonSurname"),
                                             Age = (int)d.Element("PersonAge"),
                                         },

                            PersonId = (int)g.Element("PersonId"),
                            PersonName = (string)g.Element("PersonName"),
                            PersonSurname = (string)g.Element("PersonSurname"),
                            PersonAge = (int)g.Element("PersonAge"),
                            Products = g.Elements("Products")
                                .Select(p => new Product
                                {
                                    Id = (int)p.Element("ProductId"),
                                    ProductName = (string)p.Element("ProductName")
                                }).ToList()
                        };

            foreach (var g in group)
            {
                GroupList.Add(g);
            }

        }

但是我收到错误，因为Person不是IEnumerable。但是因为每组只有1个人，所以我不想让它成为IEnumerable。有办法解决这个问题吗？

感谢您的帮助和时间

Answer 1

最好声明新的范围变量，该变量将保留<Person>元素并在以后使用

var group = from g in xdoc.Descendants("Group")
            let person = g.Element("Person") // here
            where (int)g.Element("Id") == id
            select new Group {
               ...
            }

并使用它：

 Person = new Person {
            Id = (int)person.Element("PersonId"),
            Name = (string)person.Element("PersonName"),
            Surname = (string)person.Element("PersonSurname"),
            Age = (int)person.Element("PersonAge")
          },

您还可以添加null检查xml中是否可能没有person元素：

 Person = (person == null) ? null : 
           new Person {
              Id = (int)person.Element("PersonId"),
              Name = (string)person.Element("PersonName"),
              Surname = (string)person.Element("PersonSurname"),
              Age = (int)person.Element("PersonAge")
           },

Answer 2

听起来你可以做：

Person = (from d in g.Elements("Person")
          select new Person
          {
              Id = (int)d.Element("PersonId"),
              Name = (string)d.Element("PersonName"),
              Surname = (string)d.Element("PersonSurname"),
              Age = (int)d.Element("PersonAge"),
          }).First()

但最好写一下：

Person = Person.FromXElement(g.Element("Person"))

其中FromXElement是Person中的静态方法，如下所示：

public static Person FromXElement(XElement element)
{
    return new Person
    {
        Id = (int) element.Element("PersonId"),
        Name = (string) element.Element("PersonName"),
        Surname = (string) element.Element("PersonSurname"),
        Age = (int) element.Element("PersonAge")
    };
}

这样你的查询就会更加清晰。

使用LINQ从XML检索元素

2 个答案: