XML通过使用StringBuilder的序列化的XmlWriter是utf-16，同时通过流为UTF-8？

问题描述

我很惊讶，当我遇到它，并写了一个控制台应用程序进行检查，并确保我没有做任何事情。

任何人都可以解释一下吗？

下面的代码：

 使用系统; 
使用System.Collections.Generic; 
：使用System.IO; 
使用System.Linq的; 
使用System.Text; 
使用的System.Xml; 
使用的System.Xml.Serialization; 
 
命名ConsoleApplication1 
 {
公共类节目
 {
静态无效的主要（字串[] args）
 {
变种O =新SomeObject {字段1 =字符串值，字段2 = 8}; 
 
 Console.WriteLine（ObjectToXmlViaStringBuilder）; 
 Console.Write（ObjectToXmlViaStringBuilder（O））; 
 Console.WriteLine（）; 
 Console.WriteLine（）; 
 Console.WriteLine（ObjectToXmlViaStream）; 
 Console.Write（StreamToString（ObjectToXmlViaStream（O）））; 
 Console.ReadKey（）; 
} 
 
公共静态字符串ObjectToXmlViaStringBuilder（SomeObject someObject）
 {
无功输出=新的StringBuilder（）; 
 VAR设置=新XmlWriterSettings {编码= Encoding.UTF8，缩进= TRUE}; 
 
使用（VAR的XmlWriter = XmlWriter.Create（输出设置））
 {
无功序列化=新的XmlSerializer（typeof运算（SomeObject））; 
变种命名空间=新XmlSerializerNamespaces（）; 
 
 xmlWriter.WriteStartDocument（）; 
 xmlWriter.WriteDocType（字段1，NULL，someObject.dtd，NULL）; 
 namespaces.Add（的String.Empty，的String.Empty）; 
 serializer.Serialize（XmlWriter的，someObject，命名空间）; 
} 
 
返回output.ToString（）; 
} 
 
私人静态字符串StreamToString（流流）
 {
变种读者=新的StreamReader（流）; 
返回reader.ReadToEnd（）; 
} 
 
公共静态流ObjectToXmlViaStream（SomeObject someObject）
 {
无功输出=新的MemoryStream（）; 
 VAR设置=新XmlWriterSettings {编码= Encoding.UTF8，缩进= TRUE}; 
 
使用（VAR的XmlWriter = XmlWriter.Create（输出设置））
 {
无功序列化=新的XmlSerializer（typeof运算（SomeObject））; 
变种命名空间=新XmlSerializerNamespaces（）; 
 
 xmlWriter.WriteStartDocument（）; 
 xmlWriter.WriteDocType（字段1，NULL，someObject.dtd，NULL）; 
 namespaces.Add（的String.Empty，的String.Empty）; 
 serializer.Serialize（XmlWriter的，someObject，命名空间）; 
} 
 
 output.Seek（0L，SeekOrigin.Begin）; 
 
返回输出; 
} 
 
公共类SomeObject 
 {
公共字符串字段1 {搞定;组; } 
公众诠释场2 {搞定;组; } 
} 
} 
} 
  

这是结果：

ObjectToXmlViaStringBuilder

 <？XML版本=1.0编码=UTF-16>？; 
<！DOCTYPE字段1 SYSTEMsomeObject.dtd> 
< SomeObject> 
<&字段1 GT;字符串值< /字段1> 
<&字段2 GT; 8示/场2> 
< / SomeObject> 
  

ObjectToXmlViaStream

 <？XML版本=1.0编码=UTF-8>？; 
<！DOCTYPE字段1 SYSTEMsomeObject.dtd> 
< SomeObject> 
<&字段1 GT;字符串值< /字段1> 
<&字段2 GT; 8示/场2> 
< / SomeObject> 
  

解决方案

当你创建一个的XmlWriter 围绕的TextWriter 的的XmlWriter 总是使用基本的<$ C $的编码C>的TextWriter 。的的StringWriter 始终是UTF-16，因为这是字符串如何.NET是内部编码的编码。

当您创建一个的XmlWriter 围绕流，也没有为流，因此它使用了 XmlWriterSettings 。

指定的编码

I was surprised when I encountered it, and wrote a console application to check it and make sure I wasn't doing anything else.

Can anyone explain this?

Here's the code:

using System;    
using System.Collections.Generic;
using System.IO;
using System.Linq;
using System.Text;
using System.Xml;
using System.Xml.Serialization;

namespace ConsoleApplication1
{
    public class Program
    {
        static void Main(string[] args)
        {
            var o = new SomeObject { Field1 = "string value", Field2 = 8 };

            Console.WriteLine("ObjectToXmlViaStringBuilder");
            Console.Write(ObjectToXmlViaStringBuilder(o));
            Console.WriteLine();
            Console.WriteLine();
            Console.WriteLine("ObjectToXmlViaStream");
            Console.Write(StreamToString(ObjectToXmlViaStream(o)));
            Console.ReadKey();
        }

        public static string ObjectToXmlViaStringBuilder(SomeObject someObject)
        {
            var output = new StringBuilder();
            var settings = new XmlWriterSettings { Encoding = Encoding.UTF8, Indent = true };

            using (var xmlWriter = XmlWriter.Create(output, settings))
            {
                var serializer = new XmlSerializer(typeof(SomeObject));
                var namespaces = new XmlSerializerNamespaces();

                xmlWriter.WriteStartDocument();
                xmlWriter.WriteDocType("Field1", null, "someObject.dtd", null);
                namespaces.Add(string.Empty, string.Empty);
                serializer.Serialize(xmlWriter, someObject, namespaces);
            }

            return output.ToString();
        }

        private static string StreamToString(Stream stream)
        {
            var reader = new StreamReader(stream);
            return reader.ReadToEnd();
        }

        public static Stream ObjectToXmlViaStream(SomeObject someObject)
        {
            var output = new MemoryStream();
            var settings = new XmlWriterSettings { Encoding = Encoding.UTF8, Indent = true };

            using (var xmlWriter = XmlWriter.Create(output, settings))
            {
                var serializer = new XmlSerializer(typeof(SomeObject));
                var namespaces = new XmlSerializerNamespaces();

                xmlWriter.WriteStartDocument();
                xmlWriter.WriteDocType("Field1", null, "someObject.dtd", null);
                namespaces.Add(string.Empty, string.Empty);
                serializer.Serialize(xmlWriter, someObject, namespaces);
            }

            output.Seek(0L, SeekOrigin.Begin);

            return output;
        }

        public class SomeObject
        {
            public string Field1 { get; set; }
            public int Field2 { get; set; }
        }
    }
}

This is the result:

ObjectToXmlViaStringBuilder

<?xml version="1.0" encoding="utf-16"?>
<!DOCTYPE Field1 SYSTEM "someObject.dtd">
<SomeObject>
<Field1>string value</Field1>
<Field2>8</Field2>
</SomeObject>

ObjectToXmlViaStream

<?xml version="1.0" encoding="utf-8"?>
<!DOCTYPE Field1 SYSTEM "someObject.dtd">
<SomeObject>
<Field1>string value</Field1>
<Field2>8</Field2>
</SomeObject>

解决方案

When you create an XmlWriter around a TextWriter, the XmlWriter always uses the encoding of the underlying TextWriter. The encoding of a StringWriter is always UTF-16, since that's how .NET strings are encoded internally.

When you create an XmlWriter around a Stream, there is no encoding defined for the Stream, so it uses the encoding specified in the XmlWriterSettings.

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