如何最好地检测XML文件中的编码？

Question

要使用任意编码加载XML文件,我有以下代码:

Encoding encoding;
using (var reader = new XmlTextReader(filepath))
{
    reader.MoveToContent();
encoding = reader.Encoding;
}

var settings = new XmlReaderSettings { NameTable = new NameTable() };
var xmlns = new XmlNamespaceManager(settings.NameTable);
var context = new XmlParserContext(null, xmlns, "", XmlSpace.Default, 
    encoding);
using (var reader = XmlReader.Create(filepath, settings, context))
{
    return XElement.Load(reader);
}

这有效,但打开文件两次似乎有点低效.是否有更好的方法来检测编码,以便我可以这样做:

 1. Open file
 2. Detect encoding
 3. Read XML into an XElement
 4. Close file

Answer 1

好的,我应该早点想到这个.XmlTextReader(它给我们编码)和XmlReader.Create(允许我们指定编码)都接受一个Stream.那么首先打开一个FileStream,然后将它与XmlTextReader和XmlReader一起使用,如下所示:

using (var txtreader = new FileStream(filepath, FileMode.Open))
{
    using (var xmlreader = new XmlTextReader(txtreader))
    {
        // Read in the encoding info
        xmlreader.MoveToContent();
        var encoding = xmlreader.Encoding;

        // Rewind to the beginning
        txtreader.Seek(0, SeekOrigin.Begin);

        var settings = new XmlReaderSettings { NameTable = new NameTable() };
        var xmlns = new XmlNamespaceManager(settings.NameTable);
        var context = new XmlParserContext(null, xmlns, "", XmlSpace.Default,
                 encoding);

        using (var reader = XmlReader.Create(txtreader, settings, context))
        {
            return XElement.Load(reader);
        }
    }
}

这就像一个魅力.以独立于编码的方式读取XML文件本来应该更优雅,但至少我只打开了一个文件.