10.6.4 Json文件操作
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Json格式作为轻量级数据交换格式，在网页上也得到大量应用。Json格式与XML格式各有优缺点，本书中不作讨论，请自行查找相关资料。
在实际使用Json时，需要对它进行序列化或者反序列化。所谓序列化就是将对象转换为Json字符串；而反序列化就是将Json格式字符串转换为指定类型的对象。
C#中支持对Json序列化和反序列化的类有两个：JavaScriptSerializer类和DataContractJsonSerializer类。其中：
JavaScriptSerializer类需要引用System.Web.Extensions程序集，然后在所有代码前加上：
using System.Web.Script.Serialization;
DataContractJsonSerializer类需要引用System.Runtime.Serialization程序集，然后在所有代码前加上：
using System.Runtime.Serialization.Json;
具体的引用方法是，单击菜单【项目】|【添加引用】，弹出【引用管理器】窗口，单击【程序集】|【框架】，从中间部分找到并勾选相应的程序集名称，最后按下“确定”按钮即可。
本节教程使用到用来序列化和反序列化的类：
public class Book
{
public string ISBN;
public string Title;
public float Price;
public string Year;
}
public class BookStore
{
public Book book;
}
public class Books
{
public BookStore bookstore;
}
public class BookStoreArray
{
public Book book;
}
public class BooksArray
{
public string Name;
public BookStoreArray[] bookstore;
}
注意：在将类对象序列化为Json字符串时，类对象成员变量的名称将转为Json中的数据名称，类对象成员变量相应的值转为Json中的数据值。反序列化时，定义类对象成员变量的名称需要和Json中的数据名称一致，否则不能获取对应的数据值。
10.6.4.1 JavaScriptSerializer类
JavaScriptSerializer类为Json（启用AJAX的应用程序）提供序列化和反序列化功能。
JavaScriptSerializer重要方法：
- Serialize：序列化，将对象转换为Json字符串。
- Deserialize：反序列化，将Json格式字符串转换为指定类型的对象。
【例 10.27】【项目：code10-027】使用JavaScriptSerializer生成和解析Json格式。
//序列化
private void Button1_Click(object sender, EventArgs e)
{
Books newbooks = new Books();
BookStore newBook = new BookStore();
Book newSingleBook = new Book();
newSingleBook.ISBN = "9787302425274";
newSingleBook.Title = "星球大战：克隆人的进攻";
newSingleBook.Price = 48.0f;
newSingleBook.Year = "1985";
newBook.book = newSingleBook;
newbooks.bookstore = newBook;
//声明并实例化JavaScriptSerializer
JavaScriptSerializer serializer = new JavaScriptSerializer();
string strNewBook;
//序列化，将Books类对象转为Json字符串
strNewBook = serializer.Serialize(newbooks);
//显示序列化后的结果
textBox1.Text = strNewBook;
}
//反序列化
private void Button2_Click(object sender, EventArgs e)
{
//声明并实例化JavaScriptSerializer
JavaScriptSerializer serializer = new JavaScriptSerializer();
string strNewBook = textBox1.Text;
Books newBooks = new Books();
//反序列化，将Json字符串转换为Books类对象
newBooks = serializer.Deserialize<Books>(strNewBook);
textBox2.Text += "---------------" + "\r\n";
textBox2.Text += "ISBN：" + newBooks.bookstore.book.ISBN + "\r\n";
textBox2.Text += "Title：" + newBooks.bookstore.book.Title + "\r\n";
textBox2.Text += "Price：" + newBooks.bookstore.book.Price + "\r\n";
textBox2.Text += "Year：" + newBooks.bookstore.book.Year + "\r\n";
}
//序列化数组
private void Button3_Click(object sender, EventArgs e)
{
BooksArray newBooks = new BooksArray();
newBooks.Name = "星球大战系列";
newBooks.bookstore= new BookStoreArray[3];
Book newSingleBook = new Book();
newSingleBook.ISBN = "9787302425274";
newSingleBook.Title = "星球大战：克隆人的进攻";
newSingleBook.Price = 48.0f;
newSingleBook.Year = "1985";
BookStoreArray newBook = new BookStoreArray();
newBook.book = newSingleBook;
newBooks.bookstore[0] = newBook;
newSingleBook = new Book();
newSingleBook.ISBN = "9787302426899";
newSingleBook.Title = "星球大战：西斯的复仇";
newSingleBook.Price = 58.0f;
newSingleBook.Year = "1985";
newBook = new BookStoreArray();
newBook.book = newSingleBook;
newBooks.bookstore[1] = newBook;
newSingleBook = new Book();
newSingleBook.ISBN = "99787302421146";
newSingleBook.Title = "星球大战：新的希望";
newSingleBook.Price = 35.0f;
newSingleBook.Year = "1985";
newBook = new BookStoreArray();
newBook.book = newSingleBook;
newBooks.bookstore[2] = newBook;
JavaScriptSerializer serializer = new JavaScriptSerializer();
string strNewBook;
strNewBook = serializer.Serialize(newBooks);
textBox1.Text = strNewBook;
}
//反序列化数组
private void Button4_Click(object sender, EventArgs e)
{
JavaScriptSerializer serializer = new JavaScriptSerializer();
string strNewBook = textBox1.Text;
BooksArray newBooks = new BooksArray();
newBooks = serializer.Deserialize<BooksArray>(strNewBook);
textBox2.Text += newBooks.Name + "\r\n";
for(int i = 0;i<= newBooks.bookstore.Length - 1;i++)
{
textBox2.Text += "---------------" + "\r\n";
textBox2.Text += "ISBN：" + newBooks.bookstore[i].book.ISBN + "\r\n";
textBox2.Text += "Title：" + newBooks.bookstore[i].book.Title + "\r\n";
textBox2.Text += "Price：" + newBooks.bookstore[i].book.Price + "\r\n";
textBox2.Text += "Year：" + newBooks.bookstore[i].book.Year + "\r\n";
}
}
运行结果如下图所示：
图10-16 序列化和反序列化Json数组
10.6.4.2 DataContractJsonSerializer类
DataContractJsonSerializer类将对象序列化为 Json数据，或将Json数据反序列化为对象。
DataContractJsonSerializer构造函数其中一个重载版本：
public DataContractJsonSerializer(Type type )
参数说明：
- type：表示序列化或反序列化的实例的类型。在实际使用中可以使用typeof(类型)方法来获取。
DataContractJsonSerializer常用方法：
- WriteObject：将指定对象序列化为Json数据，其中一个重载版本：
public override void WriteObject(Stream stream, Object graph );
- stream：要写入的流。
- graph：包含要写入流的数据的对象。
- ReadObject：读取Json格式流，并返回反序列化的对象。其中一个重载版本：
public override Object ReadObject(Stream stream);
- stream：要读取的Stream。
【例 10.28】【项目：code10-028】使用DataContractJsonSerializer生成和解析Json格式。
//序列化
private void Button1_Click(object sender, EventArgs e)
{
Books newbooks = new Books();
BookStore newBook = new BookStore();
Book newSingleBook = new Book();
newSingleBook.ISBN = "9787302425274";
newSingleBook.Title = "星球大战：克隆人的进攻";
newSingleBook.Price = 48.0f;
newSingleBook.Year = "1985";
newBook.book = newSingleBook;
newbooks.bookstore = newBook;
//使用GetType方法获得Books的Type对象
DataContractJsonSerializer serializer = new DataContractJsonSerializer(typeof(Books));
System.IO.MemoryStream ms = new System.IO.MemoryStream();
//将指定对象序列化为Json数据并写入流
serializer.WriteObject(ms, newbooks);
Byte[] json;
json = ms.ToArray();
ms.Close();
///将字节数组按照编码转换为字符串
string strNewBook = System.Text.Encoding.UTF8.GetString(json);
textBox1.Text = strNewBook;
}
//反序列化
private void Button2_Click(object sender, EventArgs e)
{
string strNewBook =textBox1.Text;
Books newBooks = new Books();
DataContractJsonSerializer serializer=new DataContractJsonSerializer(typeof(Books));
Byte[] bteNewBook;
bteNewBook = System.Text.Encoding.UTF8.GetBytes(strNewBook);
System.IO.MemoryStream ms = new System.IO.MemoryStream(bteNewBook);
newBooks = (Books)serializer.ReadObject(ms);
textBox2.Text += "---------------" + "\r\n";
textBox2.Text += "ISBN：" + newBooks.bookstore.book.ISBN + "\r\n";
textBox2.Text += "Title：" + newBooks.bookstore.book.Title + "\r\n";
textBox2.Text += "Price：" + newBooks.bookstore.book.Price + "\r\n";
textBox2.Text += "Year：" + newBooks.bookstore.book.Year + "\r\n";
}
//序列化数组
private void Button3_Click(object sender, EventArgs e)
{
BooksArray newBooks = new BooksArray();
newBooks.Name = "星球大战系列";
newBooks.bookstore = new BookStoreArray[3];
Book newSingleBook = new Book();
newSingleBook.ISBN = "9787302425274";
newSingleBook.Title = "星球大战：克隆人的进攻";
newSingleBook.Price = 48.0f;
newSingleBook.Year = "1985";
BookStoreArray newBook = new BookStoreArray();
newBook.book = newSingleBook;
newBooks.bookstore[0] = newBook;
newSingleBook = new Book();
newSingleBook.ISBN = "9787302426899";
newSingleBook.Title = "星球大战：西斯的复仇";
newSingleBook.Price = 58.0f;
newSingleBook.Year = "1985";
newBook = new BookStoreArray();
newBook.book = newSingleBook;
newBooks.bookstore[1] = newBook;
newSingleBook = new Book();
newSingleBook.ISBN = "99787302421146";
newSingleBook.Title = "星球大战：新的希望";
newSingleBook.Price = 35.0f;
newSingleBook.Year = "1985";
newBook = new BookStoreArray();
newBook.book = newSingleBook;
newBooks.bookstore[2] = newBook;
DataContractJsonSerializer serializer = new DataContractJsonSerializer(typeof(BooksArray));
System.IO.MemoryStream ms = new System.IO.MemoryStream();
serializer.WriteObject(ms, newBooks);
Byte[] json;
json = ms.ToArray();
ms.Close();
string strNewBook = System.Text.Encoding.UTF8.GetString(json);
textBox1.Text = strNewBook;
}
//反序列化数组
private void Button4_Click(object sender, EventArgs e)
{
string strNewBook = textBox1.Text;
BooksArray newBooks = new BooksArray();
DataContractJsonSerializer serializer = new DataContractJsonSerializer(typeof(BooksArray));
Byte[] bteNewBook;
bteNewBook = System.Text.Encoding.UTF8.GetBytes(strNewBook);
System.IO.MemoryStream ms =new System.IO.MemoryStream(bteNewBook);
newBooks = (BooksArray)serializer.ReadObject(ms);
textBox2.Text = newBooks.Name + "\r\n";
for (int i = 0; i <= newBooks.bookstore.Length - 1; i++)
{
textBox2.Text += "---------------" + "\r\n";
textBox2.Text += "ISBN：" + newBooks.bookstore[i].book.ISBN + "\r\n";
textBox2.Text += "Title：" + newBooks.bookstore[i].book.Title + "\r\n";
textBox2.Text += "Price：" + newBooks.bookstore[i].book.Price + "\r\n";
textBox2.Text += "Year：" + newBooks.bookstore[i].book.Year + "\r\n";
}
}
运行结果同【例 10.27】。
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