Question

我有这种扩展方法

    public static string SerializeObject<T>(this T value)
    {
        var serializer = new XmlSerializer(typeof(T));           
        var settings = new XmlWriterSettings
                       {
                        Encoding = new UTF8Encoding(true), 
                        Indent = false, 
                        OmitXmlDeclaration = false,
                        NewLineHandling = NewLineHandling.None
                       };

        using(var stringWriter = new StringWriter()) 
        {
            using(var xmlWriter = XmlWriter.Create(stringWriter, settings)) 
            {
                serializer.Serialize(xmlWriter, value);
            }

            return stringWriter.ToString();
        }
    }

但每当我调用它时，它指定的编码为utf-16，即<?xml version="1.0" encoding="utf-16"?>。我做错了什么？

Answer 1

字符串是UTF-16，因此写入StringWriter将始终使用UTF-16。如果那不是您想要的，那么使用其他TextWriter派生类，使用您喜欢的编码。

Answer 2

据我所知，StringWriter类在序列化为字符串时将始终使用UTF 16编码。您可以编写自己的覆盖类，接受不同的编码：

public class StringWriterWithEncoding : StringWriter
{
    private readonly Encoding _encoding;

    public StringWriterWithEncoding()
    {
    }

    public StringWriterWithEncoding(IFormatProvider formatProvider)
        : base(formatProvider)
    {
    }

    public StringWriterWithEncoding(StringBuilder sb)
        : base(sb)
    {
    }

    public StringWriterWithEncoding(StringBuilder sb, IFormatProvider formatProvider)
        : base(sb, formatProvider)
    {
    }


    public StringWriterWithEncoding(Encoding encoding)
    {
        _encoding = encoding;
    }

    public StringWriterWithEncoding(IFormatProvider formatProvider, Encoding encoding)
        : base(formatProvider)
    {
        _encoding = encoding;
    }

    public StringWriterWithEncoding(StringBuilder sb, Encoding encoding)
        : base(sb)
    {
        _encoding = encoding;
    }

    public StringWriterWithEncoding(StringBuilder sb, IFormatProvider formatProvider, Encoding encoding)
        : base(sb, formatProvider)
    {
        _encoding = encoding;
    }

    public override Encoding Encoding
    {
        get { return (null == _encoding) ? base.Encoding : _encoding; }
    }
}

所以你可以改用它：

using(var stringWriter = new StringWriterWithEncoding( Encoding.UTF8))
{
   ...
}

Answer 3

您应该从StringWriter派生一个具有覆盖编码属性的新类。

Answer 4

正如接受的答案所说，StringWriter默认为UTF-16（Unicode）设计。如果你想通过最终得到一个UTF-8字符串来实现它，我有两种方法可以帮你完成它：

解决方案＃1（效率不高，做法不好，但完成工作）：将其转储到文本文件并重新读取，删除文件（可能只适合对于小文件，如果你甚至想要这样做 - 只是想表明它可以完成！）

public static string SerializeObject<T>(this T value)
{
    var serializer = new XmlSerializer(typeof(T));           
    var settings = new XmlWriterSettings
                   {
                    Encoding = new UTF8Encoding(true), 
                    Indent = false, 
                    OmitXmlDeclaration = false,
                    NewLineHandling = NewLineHandling.None
                   };


    using(var xmlWriter = XmlWriter.Create("MyFile.xml", settings)) 
    {
        serializer.Serialize(xmlWriter, value);
    }

    XmlDocument xml = new XmlDocument();
    xml.Load("MyFile.xml");
    byte[] bytes = Encoding.UTF8.GetBytes(xml.OuterXml);        
    File.Delete("MyFile.xml");

    return Encoding.UTF8.GetString(bytes);

}

解决方案＃2（更好，更简单，更优雅的解决方案！）：使用StringWriter执行此操作，但使用其Encoding属性进行设置到UTF-8：

public static string SerializeObject<T>(this T value)
{
    var serializer = new XmlSerializer(typeof(T));           
    var settings = new XmlWriterSettings
                   {
                    Encoding = new UTF8Encoding(true), 
                    Indent = false, 
                    OmitXmlDeclaration = false,
                    NewLineHandling = NewLineHandling.None
                   };

    using(var stringWriter = new UTF8StringWriter())
    {
        using(var xmlWriter = XmlWriter.Create(stringWriter, settings)) 
        {
            serializer.Serialize(xmlWriter, value);
        }

        return stringWriter.ToString();
    }
}

public class UTF8StringWriter : StringWriter
{
    public override Encoding Encoding
    {
        get
        {
            return Encoding.UTF8;
        }
    }
}

Answer 5

如果您不想使用从StringWriter派生的类，那么您可以将OmitXmlDeclaration设置为false并声明自己的类，就像我请执行以下操作：

 public static string Serialize<T>(this T value, string xmlDeclaration = "<?xml version=\"1.0\"?>") where T : class, new()
        {
            if (value == null) return string.Empty;

            using (var stringWriter = new StringWriter())
            {
                var settings = new XmlWriterSettings
                {
                    Indent = true,
                    OmitXmlDeclaration = xmlDeclaration != null,
                };

                using (var xmlWriter = XmlWriter.Create(stringWriter, settings))
                {
                    var xmlSerializer = new XmlSerializer(typeof(T));

                    xmlSerializer.Serialize(xmlWriter, value);

                    var sb = new StringBuilder($"{Environment.NewLine}{stringWriter}");

                    sb.Insert(0, xmlDeclaration);

                    return sb.ToString();
                }
            }

Answer 6

@ john-saunders在回答中提到：

StringWriter将始终使用UTF-16

因此我为此目的使用了MemoryStream。

在我的情况下，我使用Windows-1251编码。

var xmlSstring = "";
using (var ms = new MemoryStream())
{
    var encoding = Encoding.GetEncoding(1251);
    var settings = new XmlWriterSettings
    {
        Indent = true,
        Encoding = encoding
    };

    using (var xmlTextWriter = XmlWriter.Create(ms, settings))
    {
        doc.Save(xmlTextWriter);
        xmlString = encoding.GetString(ms.ToArray());
    }
}

为什么XmlWriter总是输出utf-16编码？

6 个答案: