在.net 当中如何XML序列化一个Collection(转载)

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;

    }

}

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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。