XmlWriter 在 C# 中使用 StringWriter 编码 UTF-8

Question

我正在使用 C# 输出一个 xml 文件，我试图将 xml 编码值设置为 UTF-8，但它当前正在输出：

<?xml version="1.0"?>

这是我的代码：

public sealed class StringWriterWithEncoding: StringWriter {
    private readonly Encoding encoding;

    public StringWriterWithEncoding(Encoding encoding) {
        this.encoding = encoding;
    }

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

private string GetXml(JobStore jobStore) {
    StringWriterWithEncoding sw = new StringWriterWithEncoding();
    XmlWriterSettings settings = new XmlWriterSettings();
    settings.Encoding = Encoding.UTF8;
    settings.Encoding = Encoding.GetEncoding("utf-8");
    settings.Indent = true;
    using(var writer = XmlWriter.Create(sw, settings)) {
        writer.WriteStartDocument();
        writer.WriteStartElement("resources");

        writer.WriteStartElement("string");
        writer.WriteAttributeString("name");
        writer.WriteCData("value");
        writer.WriteEndElement();

        writer.WriteEndElement();
        writer.WriteEndDocument();
    }
    return sw.ToString();
}

一定是我缺少的一些简单的东西吗？

Answer 1

您的代码无法编译 -- StringWriterWithEncoding 没有无参数构造函数。或者，如果它确实有一个无参数的构造函数，也许它实际上看起来像这样？

public sealed class StringWriterWithEncoding : StringWriter
{
    private readonly Encoding encoding;

    public StringWriterWithEncoding() { }

    public StringWriterWithEncoding(Encoding encoding)
    {
        this.encoding = encoding;
    }

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

如果是这样，那将解释您的问题 - 字段 encoding 已保留其默认 (null) 值，这意味着 Encoding 返回 null，因此 XML 文件中不会出现编码。

要修复它，消除无参数构造函数，然后：

var sw = new StringWriterWithEncoding(Encoding.UTF8);

或者改无参构造函数显式设置Encoding.UTF8：

public sealed class StringWriterWithEncoding : StringWriter
{
    private readonly Encoding encoding;

    public StringWriterWithEncoding() : this(Encoding.UTF8) { }

    public StringWriterWithEncoding(Encoding encoding)
    {
        this.encoding = encoding;
    }

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

Answer 2

只需使用 XmlWriter 的输出文件名而不是 StringWriterWithEncoding：

var settings = new XmlWriterSettings
{
    Encoding = Encoding.UTF8,
    Indent = true
};

using (var writer = XmlWriter.Create(filePathName, settings))
{
    ...