Question

具有包含汽车收藏的XML：

<?xml version="1.0" encoding="utf-8"?>
<CarCollection>
    <Cars>
        <Car>
            <StockNumber>1020</StockNumber>
            <Make>Nissan</Make>
            <Model>Sentra</Model>
        </Car>
        <Car>
            <StockNumber>1010</StockNumber>
            <Make>Toyota</Make>
            <Model>Corolla</Model>
        </Car>
        <Car>
            <StockNumber>1111</StockNumber>
            <Make>Honda</Make>
            <Model>Accord</Model>
        </Car>
        <Car>
            <StockNumber>2000</StockNumber>
            <Make>Maybach</Make>
            <Model>S 600</Model>
        </Car>
        <Car>
            <StockNumber>2001</StockNumber>
            <Make>Ferrari</Make>
            <Model>F355 Spider</Model>
        </Car>
    </Cars>
</CarCollection>

及其反序列化的对象类，它们是由xsd.exe生成的：

//------------------------------------------------------------------------------
// <auto-generated>
//     Dieser Code wurde von einem Tool generiert.
//     Laufzeitversion:4.0.30319.42000
//
//     Änderungen an dieser Datei können falsches Verhalten verursachen und gehen verloren, wenn
//     der Code erneut generiert wird.
// </auto-generated>
//------------------------------------------------------------------------------

using System.Xml.Serialization;

// 
// Dieser Quellcode wurde automatisch generiert von xsd, Version=4.6.1055.0.
// 


/// <remarks/>
[System.CodeDom.Compiler.GeneratedCodeAttribute("xsd", "4.6.1055.0")]
[System.SerializableAttribute()]
[System.Diagnostics.DebuggerStepThroughAttribute()]
[System.ComponentModel.DesignerCategoryAttribute("code")]
[System.Xml.Serialization.XmlTypeAttribute(AnonymousType=true)]
[System.Xml.Serialization.XmlRootAttribute(Namespace="", IsNullable=false)]
public partial class CarCollection : object, System.ComponentModel.INotifyPropertyChanged {

    private CarCollectionCars[] itemsField;

    /// <remarks/>
    [System.Xml.Serialization.XmlElementAttribute("Cars", Form=System.Xml.Schema.XmlSchemaForm.Unqualified)]
    public CarCollectionCars[] Items {
        get {
            return this.itemsField;
        }
        set {
            this.itemsField = value;
            this.RaisePropertyChanged("Items");
        }
    }

    public event System.ComponentModel.PropertyChangedEventHandler PropertyChanged;

    protected void RaisePropertyChanged(string propertyName) {
        System.ComponentModel.PropertyChangedEventHandler propertyChanged = this.PropertyChanged;
        if ((propertyChanged != null)) {
            propertyChanged(this, new System.ComponentModel.PropertyChangedEventArgs(propertyName));
        }
    }
}

/// <remarks/>
[System.CodeDom.Compiler.GeneratedCodeAttribute("xsd", "4.6.1055.0")]
[System.SerializableAttribute()]
[System.Diagnostics.DebuggerStepThroughAttribute()]
[System.ComponentModel.DesignerCategoryAttribute("code")]
[System.Xml.Serialization.XmlTypeAttribute(AnonymousType=true)]
public partial class CarCollectionCars : object, System.ComponentModel.INotifyPropertyChanged {

    private CarCollectionCarsCar[] carField;

    /// <remarks/>
    [System.Xml.Serialization.XmlElementAttribute("Car", Form=System.Xml.Schema.XmlSchemaForm.Unqualified)]
    public CarCollectionCarsCar[] Car {
        get {
            return this.carField;
        }
        set {
            this.carField = value;
            this.RaisePropertyChanged("Car");
        }
    }

    public event System.ComponentModel.PropertyChangedEventHandler PropertyChanged;

    protected void RaisePropertyChanged(string propertyName) {
        System.ComponentModel.PropertyChangedEventHandler propertyChanged = this.PropertyChanged;
        if ((propertyChanged != null)) {
            propertyChanged(this, new System.ComponentModel.PropertyChangedEventArgs(propertyName));
        }
    }
}

/// <remarks/>
[System.CodeDom.Compiler.GeneratedCodeAttribute("xsd", "4.6.1055.0")]
[System.SerializableAttribute()]
[System.Diagnostics.DebuggerStepThroughAttribute()]
[System.ComponentModel.DesignerCategoryAttribute("code")]
[System.Xml.Serialization.XmlTypeAttribute(AnonymousType=true)]
public partial class CarCollectionCarsCar : object, System.ComponentModel.INotifyPropertyChanged {

    private string stockNumberField;

    private string makeField;

    private string modelField;

    /// <remarks/>
    [System.Xml.Serialization.XmlElementAttribute(Form=System.Xml.Schema.XmlSchemaForm.Unqualified)]
    public string StockNumber {
        get {
            return this.stockNumberField;
        }
        set {
            this.stockNumberField = value;
            this.RaisePropertyChanged("StockNumber");
        }
    }

    /// <remarks/>
    [System.Xml.Serialization.XmlElementAttribute(Form=System.Xml.Schema.XmlSchemaForm.Unqualified)]
    public string Make {
        get {
            return this.makeField;
        }
        set {
            this.makeField = value;
            this.RaisePropertyChanged("Make");
        }
    }

    /// <remarks/>
    [System.Xml.Serialization.XmlElementAttribute(Form=System.Xml.Schema.XmlSchemaForm.Unqualified)]
    public string Model {
        get {
            return this.modelField;
        }
        set {
            this.modelField = value;
            this.RaisePropertyChanged("Model");
        }
    }

    public event System.ComponentModel.PropertyChangedEventHandler PropertyChanged;

    protected void RaisePropertyChanged(string propertyName) {
        System.ComponentModel.PropertyChangedEventHandler propertyChanged = this.PropertyChanged;
        if ((propertyChanged != null)) {
            propertyChanged(this, new System.ComponentModel.PropertyChangedEventArgs(propertyName));
        }
    }
}

我想查询StockNumber，Make和Car类的Model。因此，我从以下代码开始：

XmlSerializer ser = new XmlSerializer(typeof(CarCollection));
CarCollection cars;
using (XmlReader reader = XmlReader.Create(file))
{
    cars = (CarCollection)ser.Deserialize(reader);
    foreach (var item in cars.Items)
    {
        foreach (var carCollection in item.Car)
        {
            carPool.Add(new CarPool()
            {
                Make = carCollection.Make,
                Model = carCollection.Model,
                StockNumber = carCollection.StockNumber
            });
        }
    }
}

但是，我不喜欢嵌套嵌套循环。有人知道如何使用LINQ来更有效地查询吗？

Answer 1

如果要解析XML，并且使用XmlSerializer，则需要管理类层次结构及其繁琐的工作来管理复杂和大型xml的类层次结构

所以一种选择是使用XDocument。

您只需在XDocument上使用LINQ即可从XML中获取所需的数据。

通过使用XDocument，您可以直接集中精力处理数据，而无需管理类结构。

XDocument xdoc = XDocument.Load(@"Path to your xml file");

var result = (from car in xdoc.Descendants("Car")
              select new
              {
                  StockNumber = car.Element("StockNumber")?.Value,
                  Make = car.Element("Make")?.Value,
                  Model = car.Element("Model")?.Value
              }).ToList();


Console.WriteLine("StockNumber\tMake\t\tModel");
Console.WriteLine("----------------------------------------------");
foreach (var item in result)
{
    Console.WriteLine(item.StockNumber + "\t\t" + item.Make + "\t\t" + item.Model); ;
}

替代：

仍然要使用XmlSerializer反序列化xml，然后下面的类是类结构，

[XmlRoot("Car")]
public class Car
{
    [XmlElement("StockNumber")]
    public string StockNumber { get; set; }
    [XmlElement("Make")]
    public string Make { get; set; }
    [XmlElement("Model")]
    public string Model { get; set; }
}
[XmlRoot("Cars")]
public class Cars
{
    [XmlElement("Car")]
    public List<Car> Car { get; set; }
}
[XmlRoot("CarCollection")]
public class CarCollection
{
    [XmlElement("Cars")]
    public Cars Cars { get; set; }
}

用法：

XmlSerializer ser = new XmlSerializer(typeof(CarCollection));

CarCollection cars = null;

using (StreamReader reader = new StreamReader(@"Path to your xml file"))
{
    cars = (CarCollection)ser.Deserialize(reader);
}

List<Car> result = cars.Cars.Car.ToList();

//--------------------------Print the result to console--------------

Console.WriteLine("StockNumber\tMake\t\tModel");
Console.WriteLine("----------------------------------------------");
foreach (var item in result)
{
    Console.WriteLine(item.StockNumber + "\t\t" + item.Make + "\t\t" + item.Model); ;
}

Console.ReadLine();

输出：

Answer 2

Linq和SelectMany（）应该解决嵌套循环：

// not tested or compiled
using (XmlReader reader = XmlReader.Create(file))
{
    var cars = (CarCollection)ser.Deserialize(reader);

    carPool.AddRange(
       cars.Items.SelectMany(it => it.Car).Select(c => 
            new CarPool()
            {
                Make = c.Make,
                Model = c.Model,
                StockNumber = c.StockNumber
            }) );
}

查询反序列化对象

2 个答案: