Question

I’m using XDocument to load and save a config file. Most of the time it works correctly, but there are cases (seemingly random) where it appends extra information after the last tag. Here’s a gist of what’s happening.

Config file pre-run:

<?xml version="1.0" encoding="us-ascii"?>
<local>
</local>

code:

XDocument config = new XDocument();
config = XDocument.Load(new FileStream(@"c:\foo.xml", FileMode.Open, FileAccess.Read));
XElement fileEle = config.Root.Element("files");
XElement statsEle = new XElement("stats");
statsEle.Add(new XElement("one", "two"));
statsEle.Add(new XElement("three", "four"));
.
.
.
fileEle.Add(statsEle);
config.Save(new FileStream(@"c:\foo.xml", FileMode.Create, FileAccess.Write), SaveOptions.None);

config file post-run:

<?xml version="1.0" encoding="us-ascii"?>
<local>
    <files>
        <one>two</one>
        <three>four</three>
    </files>
</local>s>
</local>

Any suggestions? No idea why the extra characters are being added. Sometimes it’s the extra tag, sometimes it’s different characters and sometimes it works correctly. I’ve tried loading/saving using different methods (XMLReader, etc.), adding XML tags different ways.. after X runs they all produce the same error. Thanks for the help!

Answer 1

You have two FileStream‘s open for the same file concurrently… one for reading foo.xml, and one for overwriting it. That seems very problematic.

I’d recommend:

• Disposing of the read FileStream as soon as your XmlDocument is loaded:

using (FileStream fs = new FileStream(@"C:\foo.xml", FileMode.Open, FileAccess.Read))
{
    config.Load(fs);
}

• Use FileMode.Truncate in your write FileStream so that the file is truncated to 0 bytes before you start writing to it.