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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