C# 如何更改TextWriter对象中的编码？

我在另一个resurse中使用API发送xml。我通过XDocument创建它：

XDocument xDoc = new XDocument(
    new XDeclaration("1.0", "utf-8", "yes"),
    new XElement("Entity",new XAttribute("Type", "attribute1"),
        new XElement("Fields",...

当我把它放在请求中时，它没有声明就发送了。因此，我下一步要做：

StringBuilder builder = new StringBuilder();
TextWriter writer = new StringWriter(builder);

using (writer)
{
    xDoc.Save(writer);
}

但是现在TextWriter将xml中的编码更改为utf-16。我需要在utf-8上再次更改它。

试试看

TextWriter ws = new StreamWriter(path, true, Encoding.UTF8);

或

---

这似乎有点奇怪，但如果要在xml中使用utf-8编码输出到

string

，则必须对

StringWriter

进行子类化

public class Program
{
    public static void Main(string[] args)
    {
        XDocument xDoc = new XDocument(
            new XDeclaration("1.0", "utf-8", "yes"),
            new XElement("Entity",new XAttribute("Type", "attribute1")));

        StringBuilder builder = new StringBuilder();
        using (TextWriter writer = new EncodingStringWriter(builder, Encoding.UTF8))
        {
            xDoc.Save(writer);
        }

        Console.WriteLine(builder.ToString());
    }
}

public class EncodingStringWriter : StringWriter
{
    private readonly Encoding _encoding;

    public EncodingStringWriter(StringBuilder builder, Encoding encoding) : base(builder)
    {
        _encoding = encoding;
    }

    public override Encoding Encoding
    {
        get { return _encoding;  }                
    }
}

---

或者

Encoding.GetEncoding（1256）

如果您需要特定的代码页（1256是阿拉伯语）

StreamWriter

似乎是显而易见的解决方案，是的；毕竟，它是

TextWriter

的特定编码自定义实现，是

XDocument.Save

所期望的类型。即使只是返回到字符串（但要正确使用XML声明），我也只是在

MemoryStream

上使用它。

public class Program
{
    public static void Main(string[] args)
    {
        XDocument xDoc = new XDocument(
            new XDeclaration("1.0", "utf-8", "yes"),
            new XElement("Entity",new XAttribute("Type", "attribute1")));

        StringBuilder builder = new StringBuilder();
        using (TextWriter writer = new EncodingStringWriter(builder, Encoding.UTF8))
        {
            xDoc.Save(writer);
        }

        Console.WriteLine(builder.ToString());
    }
}

public class EncodingStringWriter : StringWriter
{
    private readonly Encoding _encoding;

    public EncodingStringWriter(StringBuilder builder, Encoding encoding) : base(builder)
    {
        _encoding = encoding;
    }

    public override Encoding Encoding
    {
        get { return _encoding;  }                
    }
}