XmlReader/Writer 是顺序访问流。您必须在一端读入,以您想要的方式处理流,然后在另一端写出。优点是您不需要将整个内容读入内存并构建 DOM,这是您使用任何基于 XmlDocument 的方法所获得的。
这个方法应该让你开始:
private static void PostProcess(Stream inStream, Stream outStream)
{
var settings = new XmlWriterSettings() { Indent = true, IndentChars = " " };
using (var reader = XmlReader.Create(inStream))
using (var writer = XmlWriter.Create(outStream, settings)) {
while (reader.Read()) {
switch (reader.NodeType) {
case XmlNodeType.Element:
writer.WriteStartElement(reader.Prefix, reader.Name, reader.NamespaceURI);
writer.WriteAttributes(reader, true);
//
// check if this is the node you want, inject attributes here.
//
if (reader.IsEmptyElement) {
writer.WriteEndElement();
}
break;
case XmlNodeType.Text:
writer.WriteString(reader.Value);
break;
case XmlNodeType.EndElement:
writer.WriteFullEndElement();
break;
case XmlNodeType.XmlDeclaration:
case XmlNodeType.ProcessingInstruction:
writer.WriteProcessingInstruction(reader.Name, reader.Value);
break;
case XmlNodeType.SignificantWhitespace:
writer.WriteWhitespace(reader.Value);
break;
}
}
}
}
这不像派生自己的 XmlWriter 那样干净,但我发现它要容易得多。
[编辑]
如何一次打开两个流的示例可能是这样的:
using (FileStream readStream = new FileStream(@"c:\myFile.xml", FileMode.OpenOrCreate, FileAccess.Read, FileShare.Write)) {
using (FileStream writeStream = new FileStream(@"c:\myFile.xml", FileMode.OpenOrCreate, FileAccess.Write)) {
PostProcess(readStream, writeStream);
}
}