在.net
当中如何XML序列化一个Collection
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XML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XmlSerializer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XML的结构是实现固定的，你必须按照要求去生成XML结构。
使用不同的属性
可以灵活的控制生成的XML，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XML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.Xml.Serialization;
using
System.IO;
namespace
SerializeCollection
{
class
Program
{
static void Main(string [] args)
{
Program test = new
Program();
test.SerializeDocument("e://books.xml"
);
}
public void SerializeDocument(string filename)
{
// Creates a new XmlSerializer.
XmlSerializer s =
new XmlSerializer(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 objects' properties.
item1.ItemName = "Widget1"
;
item1.ItemCode = "w1"
;
item1.ItemPrice = 231;
item1.ItemQuantity = 3;
Item item2 = new
Item();
// Sets the objects' 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
{
[XmlElement(ElementName = "OrderItem"
)]
public string ItemName;
public string ItemCode;
public decimal ItemPrice;
public int ItemQuantity;
}
}
{
font-size: small;
color: black;
font-family: consolas, "Courier New", courier, monospace;
background-color: #ffffff;
/*white-space: pre;*/
}
.csharpcode pre { margin: 0em; }
.csharpcode .rem { color: #008000; }
.csharpcode .kwrd { color: #0000ff; }
.csharpcode .str { color: #006080; }
.csharpcode .op { color: #0000c0; }
.csharpcode .preproc { color: #cc6633; }
.csharpcode .asp { background-color: #ffff00; }
.csharpcode .html { color: #800000; }
.csharpcode .attr { color: #ff0000; }
.csharpcode .alt
{
background-color: #f4f4f4;
width: 100%;
margin: 0em;
}
.csharpcode .lnum { color: #606060; }
最后序列化成的XML：
<? xml version ="1.0" encoding ="utf-8" ?>
< MyRootClass xmlns:xsi ="http://www.w3.org/2001/XMLSchema-instance" xmlns:xsd ="http://www.w3.org/2001/XMLSchema" >
< 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 >
.csharpcode, .csharpcode pre
{
font-size: small;
color: black;
font-family: consolas, "Courier New", courier, monospace;
background-color: #ffffff;
/*white-space: pre;*/
}
.csharpcode pre { margin: 0em; }
.csharpcode .rem { color: #008000; }
.csharpcode .kwrd { color: #0000ff; }
.csharpcode .str { color: #006080; }
.csharpcode .op { color: #0000c0; }
.csharpcode .preproc { color: #cc6633; }
.csharpcode .asp { background-color: #ffff00; }
.csharpcode .html { color: #800000; }
.csharpcode .attr { color: #ff0000; }
.csharpcode .alt
{
background-color: #f4f4f4;
width: 100%;
margin: 0em;
}
.csharpcode .lnum { color: #606060; }
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.Xml.Serialization;
using
System.IO;
namespace
SerializeCollection
{
class
Program
{
static void Main(string [] args)
{
Program test = new
Program();
test.SerializeDocument("e://books.xml"
);
}
public void SerializeDocument(string filename)
{
// Creates a new XmlSerializer.
XmlSerializer s =
new XmlSerializer(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 objects' properties.
item1.ItemName = "Widget1"
;
item1.ItemCode = "w1"
;
item1.ItemPrice = 231;
item1.ItemQuantity = 3;
BookItem bookItem = new
BookItem();
// Sets the objects' properties.
bookItem.ItemCode = "w2"
;
bookItem.ItemPrice = 123;
bookItem.ItemQuantity = 7;
bookItem.ISBN = "34982333"
;
bookItem.Title = "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
{
[XmlElement(ElementName = "OrderItem"
)]
public string ItemName;
public string ItemCode;
public decimal ItemPrice;
public int ItemQuantity;
}
public
class
BookItem : Item
{
public
string
Title;
public
string
Author;
public
string
ISBN;
}
}
.csharpcode, .csharpcode pre
{
font-size: small;
color: black;
font-family: consolas, "Courier New", courier, monospace;
background-color: #ffffff;
/*white-space: pre;*/
}
.csharpcode pre { margin: 0em; }
.csharpcode .rem { color: #008000; }
.csharpcode .kwrd { color: #0000ff; }
.csharpcode .str { color: #006080; }
.csharpcode .op { color: #0000c0; }
.csharpcode .preproc { color: #cc6633; }
.csharpcode .asp { background-color: #ffff00; }
.csharpcode .html { color: #800000; }
.csharpcode .attr { color: #ff0000; }
.csharpcode .alt
{
background-color: #f4f4f4;
width: 100%;
margin: 0em;
}
.csharpcode .lnum { color: #606060; }
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 XmlInclude 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XmlArrayItem
来
帮忙了。MyRootClass类的Item成员前加入XmlArrayItem标志。
[XmlArrayItem(ElementName= "Item"
,
IsNullable=true
,
Type = typeof
(Item),
Namespace = "http://www.aboutdnn.com"
),
XmlArrayItem(ElementName = "BookItem"
,
IsNullable = true
,
Type = typeof
(BookItem),
Namespace = http://www.aboutdnn.com
)]
.csharpcode, .csharpcode pre
{
font-size: small;
color: black;
font-family: consolas, "Courier New", courier, monospace;
background-color: #ffffff;
/*white-space: pre;*/
}
.csharpcode pre { margin: 0em; }
.csharpcode .rem { color: #008000; }
.csharpcode .kwrd { color: #0000ff; }
.csharpcode .str { color: #006080; }
.csharpcode .op { color: #0000c0; }
.csharpcode .preproc { color: #cc6633; }
.csharpcode .asp { background-color: #ffff00; }
.csharpcode .html { color: #800000; }
.csharpcode .attr { color: #ff0000; }
.csharpcode .alt
{
background-color: #f4f4f4;
width: 100%;
margin: 0em;
}
.csharpcode .lnum { color: #606060; }
修改后的代码如下：
using
System;
using
System.Collections.Generic;
using
System.Linq;
using
System.Text;
using
System.Xml.Serialization;
using
System.IO;
namespace
SerializeCollection
{
class
Program
{
static void Main(string [] args)
{
Program test = new
Program();
test.SerializeDocument("e://books.xml"
);
}
public void SerializeDocument(string filename)
{
// Creates a new XmlSerializer.
XmlSerializer s =
new XmlSerializer(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 objects' properties.
item1.ItemName = "Widget1"
;
item1.ItemCode = "w1"
;
item1.ItemPrice = 231;
item1.ItemQuantity = 3;
BookItem bookItem = new
BookItem();
// Sets the objects' properties.
bookItem.ItemCode = "w2"
;
bookItem.ItemPrice = 123;
bookItem.ItemQuantity = 7;
bookItem.ISBN = "34982333"
;
bookItem.Title = "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;
[XmlArrayItem(ElementName = "Item"
,
IsNullable = true
,
Type = typeof
(Item),
Namespace = "http://www.aboutdnn.com"
),
XmlArrayItem(ElementName = "BookItem"
,
IsNullable = true
,
Type = typeof
(BookItem),
Namespace = "http://www.aboutdnn.com"
)]
public
List<Item> Items
{
get { return
items; }
set { items = value
; }
}
}
public class Item
{
[XmlElement(ElementName = "OrderItem"
)]
public string ItemName;
public string ItemCode;
public decimal ItemPrice;
public int ItemQuantity;
}
public class BookItem : Item
{
public string Title;
public string Author;
public string ISBN;
}
}
.csharpcode, .csharpcode pre
{
font-size: small;
color: black;
font-family: consolas, "Courier New", courier, monospace;
background-color: #ffffff;
/*white-space: pre;*/
}
.csharpcode pre { margin: 0em; }
.csharpcode .rem { color: #008000; }
.csharpcode .kwrd { color: #0000ff; }
.csharpcode .str { color: #006080; }
.csharpcode .op { color: #0000c0; }
.csharpcode .preproc { color: #cc6633; }
.csharpcode .asp { background-color: #ffff00; }
.csharpcode .html { color: #800000; }
.csharpcode .attr { color: #ff0000; }
.csharpcode .alt
{
background-color: #f4f4f4;
width: 100%;
margin: 0em;
}
.csharpcode .lnum { color: #606060; }
序列化后的XML如下：
<? xml version ="1.0" encoding ="utf-8" ?>
< MyRootClass xmlns:xsi ="http://www.w3.org/2001/XMLSchema-instance" xmlns:xsd ="http://www.w3.org/2001/XMLSchema" >
< Items >
< Item xmlns ="http://www.aboutdnn.com" >
< OrderItem > Widget1</ OrderItem >
< ItemCode > w1</ ItemCode >
< ItemPrice > 231</ ItemPrice >
< ItemQuantity > 3</ ItemQuantity >
</ Item >
< BookItem xmlns ="http://www.aboutdnn.com" >
< ItemCode > w2</ ItemCode >
< ItemPrice > 123</ ItemPrice >
< ItemQuantity > 7</ ItemQuantity >
< Title > Book of Widgets</ Title >
< Author > John Smith</ Author >
< ISBN > 34982333</ ISBN >
</ BookItem >
</ Items >
</ MyRootClass >
.csharpcode, .csharpcode pre
{
font-size: small;
color: black;
font-family: consolas, "Courier New", courier, monospace;
background-color: #ffffff;
/*white-space: pre;*/
}
.csharpcode pre { margin: 0em; }
.csharpcode .rem { color: #008000; }
.csharpcode .kwrd { color: #0000ff; }
.csharpcode .str { color: #006080; }
.csharpcode .op { color: #0000c0; }
.csharpcode .preproc { color: #cc6633; }
.csharpcode .asp { background-color: #ffff00; }
.csharpcode .html { color: #800000; }
.csharpcode .attr { color: #ff0000; }
.csharpcode .alt
{
background-color: #f4f4f4;
width: 100%;
margin: 0em;
}
.csharpcode .lnum { color: #606060; }
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XML中<Items>节点的名字或者添加属
性，XmlArrayAttribute
可
以帮你的忙，这个你可以自己试试。