Question

我正在使用LINQ从XML文件中查找对象。找到对象后，我想打印其细节，但我不确定如何使用我找到的对象。

这是我的代码：

var apartmentExist =
    from apartment1 in apartmentXml.Descendants("Apartment")
    where (apartment1.Attribute("street_name").Value == newApartment.StreetName) &&
          (apartment1.Element("Huose_Num").Value == newApartment.HouseNum.ToString())
    select apartment1.Value;
if (apartmentExist.Any() == false)
{
    Console.WriteLine("Sorry, Apartment at {0} or at num {1}", newApartment.StreetName,
        newApartment.HouseNum);

}
else
{

    //print the details of apartment1
}

我的XML是：

<?xml version="1.0" encoding="utf-8"?>
<Apartments>
  <Apartment street_name="sumsum">
    <Huose_Num>13</Huose_Num>
    <Num_Of_Rooms>4</Num_Of_Rooms>
    <Price>10000</Price>
    <Flags>
      <Elevator>true</Elevator>
      <Floor>1</Floor>
      <parking_spot>true</parking_spot>
      <balcony>true</balcony>
      <penthouse>true</penthouse>
      <status_sale>true</status_sale>
    </Flags>
  </Apartment>
</Apartments>

Answer 1

您LINQ查询返回IEnumerable<XElement>如果您希望它返回多个元素，您可以使用foreach循环来打印元素，如果只有一个结果，您可以调用{{ 1}}获取.Single()的扩展方法，而不是集合：
使用XElement属性将XElement转换为string更安全，因为当元素不存在时，它不会抛出XElement.Value。您还应该使用NullReferenceException强制转换并比较数字而不是(int)XElement，并将其与数字的字符串表示形式进行比较。
您不应使用XElement.Value方法，而是使用Descendants。它会使您的查询更快，因为只会处理需要搜索的元素。
您应该致电Elements并检查结果是否为FirstOrDefault，而不是使用null，然后再拨打Any来电。它会阻止您的查询执行两次。
而不是返回First，apartment1.Value，而不是返回string本身。这将是apartment1，您可以在以后必要时获取内容。
```
XElement
```

Answer 2

您可以使用以下一个linq查询来执行此操作：

var apartment =
(from a in apartmentXml.Descendants("Apartment")
where (a.Attribute("street_name").Value == newApartment.StreetName) &&
      (a.Element("Huose_Num").Value == newApartment.HouseNum.ToString())
select new { 
      street_name = a.Attribute("street_name").Value,
      Huose_Num = a.Element("Huose_Num").Value,
      Num_Of_Rooms = a.Element("Num_Of_Rooms").Value,
      Price = a.Element("Price").Value,
      Flags = (from f in a.Element("Flags")
                  select new { 
                    Elevator = f.Element("Elevator").Value,
                    Floor =  f.Element("Floor").Value,
                    parking_spot = f.Element("Floor").Value,
                    balcony = f.Element("balcony").Value,
                    penthouse = f.Element("penthouse").Value,
                    status_sale = f.Element("status_sale").Value
                    })
                 }).FirstOrDefault();

if(aparment == null) 
{
   Console.WriteLine("Sorry, Apartment at {0} or at num {1}", newApartment.StreetName,
    newApartment.HouseNum);
} 
else 
{
   Console.WriteLine(apartment.street_name);
   Console.WriteLine(apartment.Huose_Num);
   Console.WriteLine(apartment.Num_Of_Rooms);
   Console.WriteLine(apartment.Price);
   Console.WriteLine(apartment.street_name);

   Console.WriteLine(apartment.Flags.Elevator);
   Console.WriteLine(apartment.Flags.Floor);
   Console.WriteLine(apartment.Flags.parking_spot);
   Console.WriteLine(apartment.Flags.balcony);
   Console.WriteLine(apartment.Flags.penthouse);
   Console.WriteLine(apartment.Flags.status_sale);

}

Answer 3

试试这个：

var xml = @"<?xml version=""1.0"" encoding=""utf-8""?>
<Apartments>
  <Apartment street_name=""sumsum"">
    <Huose_Num>13</Huose_Num>
    <Num_Of_Rooms>4</Num_Of_Rooms>
    <Price>10000</Price>
    <Flags>
      <Elevator>true</Elevator>
      <Floor>1</Floor>
      <parking_spot>true</parking_spot>
      <balcony>true</balcony>
      <penthouse>true</penthouse>
      <status_sale>true</status_sale>
    </Flags>
  </Apartment>
</Apartments>
";

var apartmentXml = XElement.Parse( xml );
//apartmentXml.Dump(); // This is a linqpad feature

var new_street = "sumsum";
var new_house_num = "13";


var match_apartment = apartmentXml.Elements().Where (x => x.Attribute("street_name").Value ==  new_street && x.Element("Huose_Num").Value == new_house_num );
//match_apartment.Dump();

if (match_apartment.Count() < 1 )
{
    Console.WriteLine("Sorry, Apartment at {0} or at num {1}", new_street,
        new_house_num);

}
else
{
    foreach( var x in match_apartment.Elements() )
    {
        Console.WriteLine("{0} | {1}", x.Name, x.Value );
    }
}

Answer 4

appatmentExist是一个IEnumerable，因此访问其中的各个项目使用List indexing来访问单个元素

Comsole.Writeline(appartmentExist.toList()[0].StreetName);

将打印上面查询中找到的第一个元素的街道名称

使用LINQ返回的对象

4 个答案: