Lost XML file declaration using DataSet.WriteXml(Stream)

问题

I had a Dataset with some data in it. When I tried to write this DataSet into a file, everything was OK. But When I tried to write it into a MemoryStream, the XML file declaration was lost. The code looks like:

DataSet dSet = new DataSet();
//load schema, fill data in
dSet.WriteXML("testFile.xml");
MemoryStream stream = new MemoryStream();
dSet.WriteXML(stream);
stream.Seek(0,SeekOrigin.Begin);

When I opened file testFile.xml, I got:

<?xml version="1.0" standalone="yes"?>
//balabala

But When I open the stream with StreamReader, I only got:

//balabala

Somebody said I can insert XML file declaration in my stream manually. It works but seems so ugly. Do you know why it dropped the first line and any more simple solution?

回答1:

It wasn't dropped. Simply not included. Though it is highly recommend the xml declaration is not a required element of the xml specification.

http://msdn.microsoft.com/en-us/library/ms256048(VS.85).aspx

You can use XmlWriter.WriteStartDocument to include the xml declaration in the stream like so:

MemoryStream stream = new MemoryStream();
var writer = XmlWriter.Create(stream);
writer.WriteStartDocument(true);
dSet.WriteXML(stream);

回答2:

I try your solution with DataTable and don't work correctly.

using (MemoryStream stream = new MemoryStream()) {
    using (XmlTextWriter writer = new XmlTextWriter(stream, Encoding.UTF8)) {
        writer.WriteStartDocument(); //<?xml version="1.0" encoding="utf-8"?>
        writer.WriteRaw("\r\n"); //endline
        writer.Flush(); //Write immediately the stream
        dTable.WriteXml(stream);
    }
}

回答3:

If you disassemble the 2.0 code you'll see that the WriteXml method that takes a file name explictly writes out the declaration (XmlWriter.WriteStartDocument) but the WriteXml methods that take a stream or writer do not.

来源：https://stackoverflow.com/questions/392626/lost-xml-file-declaration-using-dataset-writexmlstream

标签

dataset