Collection主要是指像Array, ArrayList, List, Dictionary, HashTable这些数据类型,大家平时用的很多。如果一个类中有一个Collection类型的成员,在对这个类进行 序列化的时候,应该如何处理?应该说在.net当中这是比较简单的,只要建立一个 Serializer类就可以帮你自动搞定,不过有的时候你可能需要对自动的序列化过程施加更多的控制,比如 的结构是实现固定的,你必须按照要求去生成 结构。

使用不同的属性可以灵活的控制生成的 ,这里我就不多介绍了,主要讲一下如何序列化比较复杂的Collection结构。下面的方法,对于所有实现了IEnumerable接口的Collection都有效。

我使用MSDN中的例子,不过没有使用数组或者ArrayList,而是使用了比较高级的数据类型List<T>,希望在讲解如何序列化 的同时给使用List<T>的同学提供点参考。

序列化一个List<T>

下面的代码示范了如何序列化一个List<T>,实际上和序列化其它类一样,把这个类扔给Serialize()函数即可。

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System. .Serialization;
using System.IO;
 
namespace SerializeCollection
{
    class Program
    {
        static void Main(string[] args)
        {
            Program test = new Program();
            test.SerializeDocument("e:\books. ");
        }
 
        public void SerializeDocument(string filename)
        {
            // Creates a new  Serializer.
             Serializer s =
            new  Serializer(typeof(MyRootClass));
 
            // Writing the file requires a StreamWriter.
            TextWriter myWriter = new StreamWriter(filename);
 
            // Creates an instance of the class to serialize. 
            MyRootClass myRootClass = new MyRootClass();
            
            //create items
            Item item1 = new Item();
            // Sets the  s' properties.
            item1.ItemName = "Widget1";
            item1.ItemCode = "w1";
            item1.ItemPrice = 231;
            item1.ItemQuantity = 3;
 
            
            Item item2 = new Item();
            // Sets the  s' properties.
            item2.ItemName = "Widget2";
            item2.ItemCode = "w2";
            item2.ItemPrice = 800;
            item2.ItemQuantity = 2;
 
            // Sets the class's Items property to the list.
            myRootClass.Items.Add(item1);
            myRootClass.Items.Add(item2);
 
            /* Serializes the class, writes it to disk, and closes 
               the TextWriter. */
            s.Serialize(myWriter, myRootClass);
            myWriter.Close();
        }
 
    }
 
    // This is the class that will be serialized.
    [Serializable]
    public class MyRootClass
    {
        public MyRootClass()
        {
            items = new List<Item>();
        }
 
        private List<Item> items;
 
        public List<Item> Items
        {
            get { return items; }
            set { items = value; }
        }
    }
 
    public class Item
    {
        [ Element(ElementName = "OrderItem")]
        public string ItemName;
        public string ItemCode;
        public decimal ItemPrice;
        public int ItemQuantity;
    }
 
 
}

最后序列化成的 :

<?  version="1.0" encoding="utf-8"?>
<MyRootClass  ns:xsi="http://www.w3.org/2001/ Schema-instance"  ns:xsd="http://www.w3.org/2001/ Schema">
  <Items>
    <Item>
      <OrderItem>Widget1</OrderItem>
      <ItemCode>w1</ItemCode>
      <ItemPrice>231</ItemPrice>
      <ItemQuantity>3</ItemQuantity>
    </Item>
    <Item>
      <OrderItem>Widget2</OrderItem>
      <ItemCode>w2</ItemCode>
      <ItemPrice>800</ItemPrice>
      <ItemQuantity>2</ItemQuantity>
    </Item>
  </Items>
</MyRootClass>

如果这个List<T>中的成员的类还有继承关系

现在把情况变得复杂一点,因为多态,List<T>中的类可能是指定类型的子类型,这个时候会出现什么情况呢?

我们增加一个BookItem类,继承自Item 类。

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System. .Serialization;
using System.IO;
 
namespace SerializeCollection
{
    class Program
    {
        static void Main(string[] args)
        {
            Program test = new Program();
            test.SerializeDocument("e:\books. ");
        }
 
        public void SerializeDocument(string filename)
        {
            // Creates a new  Serializer.
             Serializer s =
            new  Serializer(typeof(MyRootClass));
 
            // Writing the file requires a StreamWriter.
            TextWriter myWriter = new StreamWriter(filename);
 
            // Creates an instance of the class to serialize. 
            MyRootClass myRootClass = new MyRootClass();
 
            /* Uses a more advanced method of creating an list:
         create instances of the Item and BookItem, where BookItem 
         is derived from Item. */
            Item item1 = new Item();
            // Sets the  s' properties.
            item1.ItemName = "Widget1";
            item1.ItemCode = "w1";
            item1.ItemPrice = 231;
            item1.ItemQuantity = 3;
 
            BookItem bookItem = new BookItem();
            // Sets the  s' properties.
            bookItem.ItemCode = "w2";
            bookItem.ItemPrice = 123;
            bookItem.ItemQuantity = 7;
            bookItem.ISBN = "34982333";
            bookItem.  = "Book of Widgets";
            bookItem.Author = "John Smith";
 
            // Sets the class's Items property to the list.
            myRootClass.Items.Add(item1);
            myRootClass.Items.Add(bookItem);
 
            /* Serializes the class, writes it to disk, and closes 
               the TextWriter. */
            s.Serialize(myWriter, myRootClass);
            myWriter.Close();
        }
 
    }
 
    // This is the class that will be serialized.
    [Serializable]
    public class MyRootClass
    {
        public MyRootClass()
        {
            items = new List<Item>();
        }
 
        private List<Item> items;
 
        public List<Item> Items
        {
            get { return items; }
            set { items = value; }
        }
    }
 
    public class Item
    {
        [ Element(ElementName = "OrderItem")]
        public string ItemName;
        public string ItemCode;
        public decimal ItemPrice;
        public int ItemQuantity;
    }
 
    
 
 
 
}

修改代码后,我们再运行,出现如下错误“不应是类型 SerializeCollection.BookItem。使用 Include 或 SoapInclude 属性静态指定非已知的类型”,看来是系统在做序列化的时候,搞不清楚List中的成员到底是什么类型。这个时候就要使用 ArrayItem来帮忙了。MyRootClass类的Item成员前加入 ArrayItem标志。

[ ArrayItem(ElementName= "Item", 
   IsNullable=true,
   Type = typeof(Item),
   Namespace = "http://www.aboutdnn.com"),
    ArrayItem(ElementName = "BookItem", 
   IsNullable = true, 
   Type = typeof(BookItem),
   Namespace = http://www.aboutdnn.com)]

修改后的代码如下:

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System. .Serialization;
using System.IO;
 
namespace SerializeCollection
{
    class Program
    {
        static void Main(string[] args)
        {
            Program test = new Program();
            test.SerializeDocument("e:\books. ");
        }
 
        public void SerializeDocument(string filename)
        {
            // Creates a new  Serializer.
             Serializer s =
            new  Serializer(typeof(MyRootClass));
 
            // Writing the file requires a StreamWriter.
            TextWriter myWriter = new StreamWriter(filename);
 
            // Creates an instance of the class to serialize. 
            MyRootClass myRootClass = new MyRootClass();
 
            /* Uses a more advanced method of creating an list:
         create instances of the Item and BookItem, where BookItem 
         is derived from Item. */
            Item item1 = new Item();
            // Sets the  s' properties.
            item1.ItemName = "Widget1";
            item1.ItemCode = "w1";
            item1.ItemPrice = 231;
            item1.ItemQuantity = 3;
 
            BookItem bookItem = new BookItem();
            // Sets the  s' properties.
            bookItem.ItemCode = "w2";
            bookItem.ItemPrice = 123;
            bookItem.ItemQuantity = 7;
            bookItem.ISBN = "34982333";
            bookItem.  = "Book of Widgets";
            bookItem.Author = "John Smith";
 
            // Sets the class's Items property to the list.
            myRootClass.Items.Add(item1);
            myRootClass.Items.Add(bookItem);
 
            /* Serializes the class, writes it to disk, and closes 
               the TextWriter. */
            s.Serialize(myWriter, myRootClass);
            myWriter.Close();
        }
 
    }
 
    // This is the class that will be serialized.
    [Serializable]
    public class MyRootClass
    {
        public MyRootClass()
        {
            items = new List<Item>();
        }
 
        private List<Item> items;
 
        
 
        public List<Item> Items
        {
            get { return items; }
            set { items = value; }
        }
    }
 
    public class Item
    {
        [ Element(ElementName = "OrderItem")]
        public string ItemName;
        public string ItemCode;
        public decimal ItemPrice;
        public int ItemQuantity;
    }
 
    public class BookItem : Item
    {
        public string  ;
        public string Author;
        public string ISBN;
    }
 
 
 
}

序列化后的 如下:

 

<?  version="1.0" encoding="utf-8"?><MyRootClass  ns:xsi="http://www.w3.org/2001/ Schema-instance"  ns:xsd="http://www.w3.org/2001/ Schema">  <Items>    <Item  ns="http://www.aboutdnn.com">      <OrderItem>Widget1</OrderItem>      <ItemCode>w1</ItemCode>      <ItemPrice>231</ItemPrice>      <ItemQuantity>3</ItemQuantity>    </Item>    <BookItem  ns="http://www.aboutdnn.com">      <ItemCode>w2</ItemCode>      <ItemPrice>123</ItemPrice>      <ItemQuantity>7</ItemQuantity>      < >Book of Widgets</ >      <Author>John Smith</Author>      <ISBN>34982333</ISBN>    </BookItem>  </Items></MyRootClass>

可以看到,已经根据不同的数据类型,序列化为不同名字的节点。这个时候,如果你还想修改 中<Items>节点的名字或者添加属性, ArrayAttribute可以帮你的忙,这个你可以自己试试。

参考文档:

ArrayAttribute Class:http://msdn.microsoft.com/en-us/library/system. .serialization. arrayattribute.aspx

对于所有控制 序列化的Attributes,请参考这里:Attributes That Control Serialization

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