如何将 xml 返回为 UTF-8 而不是 UTF-16

Question

我正在使用序列化<T> 的例程。它可以工作，但是当下载到浏览器时，我看到一个空白页面。我可以查看页面源代码或在文本编辑器中打开下载并看到 xml，但它是 UTF-16 格式，我认为这就是浏览器页面显示空白的原因？

如何修改我的序列化程序以返回 UTF-8 而不是 UTF-16？

返回的 XML 源：

<?xml version="1.0" encoding="utf-16"?>
<ArrayOfString xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:xsd="http://www.w3.org/2001/XMLSchema">
  <string>January</string>
  <string>February</string>
  <string>March</string>
  <string>April</string>
  <string>May</string>
  <string>June</string>
  <string>July</string>
  <string>August</string>
  <string>September</string>
  <string>October</string>
  <string>November</string>
  <string>December</string>
  <string />
</ArrayOfString>

对序列化程序的示例调用：

DateTimeFormatInfo dateTimeFormatInfo = new DateTimeFormatInfo();
var months = dateTimeFormatInfo.MonthNames.ToList();

string SelectionId = "1234567890";

return new XmlResult<List<string>>(SelectionId)
{
    Data = months
};

序列化器：

public class XmlResult<T> : ActionResult
{
    private string filename = DateTime.Now.ToString("ddmmyyyyhhss");

    public T Data { private get; set; }

    public XmlResult(string selectionId = "")
    {
        if (selectionId != "")
        {
            filename = selectionId;
        }
    }

    public override void ExecuteResult(ControllerContext context)
    {
        HttpContextBase httpContextBase = context.HttpContext;
        httpContextBase.Response.Buffer = true;
        httpContextBase.Response.Clear();

        httpContextBase.Response.AddHeader("content-disposition", "attachment; filename=" + filename + ".xml");
        httpContextBase.Response.ContentType = "text/xml";

        using (StringWriter writer = new StringWriter())
        {
            XmlSerializer xml = new XmlSerializer(typeof(T));
            xml.Serialize(writer, Data);
            httpContextBase.Response.Write(writer);
        }
    }
}

Answer 1

您可以使用强制使用 UTF8 的 StringWriter。这是一种方法：

public class Utf8StringWriter : StringWriter
{
    // Use UTF8 encoding but write no BOM to the wire
    public override Encoding Encoding
    {
         get { return new UTF8Encoding(false); } // in real code I'll cache this encoding.
    }
}

然后在您的代码中使用 Utf8StringWriter 编写器。

using (StringWriter writer = new Utf8StringWriter())
{
    XmlSerializer xml = new XmlSerializer(typeof(T));
    xml.Serialize(writer, Data);
    httpContextBase.Response.Write(writer);
}

答案的灵感来自Serializing an object as UTF-8 XML in .NET

Answer 2

响应编码

我对框架的这一部分不太熟悉。但根据 MSDN，您可以像这样设置content encoding of an HttpResponse：

httpContextBase.Response.ContentEncoding = Encoding.UTF8;

XmlSerializer 看到的编码

再次阅读您的问题后，我发现这是困难的部分。问题在于StringWriter 的使用。由于 .NET 字符串始终存储为 UTF-16（需要引用 ^^），StringWriter 将其作为其编码返回。因此XmlSerializer 将 XML 声明写为

<?xml version="1.0" encoding="utf-16"?>

要解决这个问题，您可以像这样写入 MemoryStream：

using (MemoryStream stream = new MemoryStream())
using (StreamWriter writer = new StreamWriter(stream, Encoding.UTF8))
{
    XmlSerializer xml = new XmlSerializer(typeof(T));
    xml.Serialize(writer, Data);

    // I am not 100% sure if this can be optimized
    httpContextBase.Response.BinaryWrite(stream.ToArray());
}

其他方法

另一个编辑：我刚刚注意到 jtm001 链接的this SO answer。浓缩的解决方案是为XmlSerializer 提供一个自定义XmlWriter，该XmlWriter 配置为使用UTF8 作为编码。

Athari proposes 派生自 StringWriter 并将编码宣传为 UTF8。

据我了解，这两种解决方案都应该可以工作。我认为这里的要点是您将需要一种样板代码或另一种......

Answer 3

序列化为 UTF8 字符串：

    private string Serialize(MyData data)
    {
        XmlSerializer ser = new XmlSerializer(typeof(MyData));
        // Using a MemoryStream to store the serialized string as a byte array, 
        // which is "encoding-agnostic"
        using (MemoryStream ms = new MemoryStream())
            // Few options here, but remember to use a signature that allows you to 
            // specify the encoding  
            using (XmlTextWriter tw = new XmlTextWriter(ms, Encoding.UTF8)) 
            {
                tw.Formatting = Formatting.Indented;
                ser.Serialize(tw, data);
                // Now we get the serialized data as a string in the desired encoding
                return Encoding.UTF8.GetString(ms.ToArray());
            }
    }

要在 Web 响应中将其作为 XML 返回，请不要忘记设置响应编码：

    string xml = Serialize(data);
    Response.ContentType = "application/xml";
    Response.ContentEncoding = System.Text.Encoding.UTF8;
    Response.Output.Write(xml);