What could cause an XML file to be filled with null characters?

Question

This is a tricky question. I suspect it will require some advanced knowledge of file systems to answer.

I have a WPF application, \"App1,\" targeting .NET framework

Answer 1

There is no documented reason for this behavior, as this is happening to users but nobody can tell the origin of this odd conditions.

It might be CLR problem, although this is a very unlikely, the CLR doesn't just write null characters and XML document cannot contain null characters if there's no xsi:nil defined for the nodes.

Anyway, the only documented way to fix this is to delete the corrupted file using this line of code:

try
{
     ConfigurationManager.OpenExeConfiguration(ConfigurationUserLevel.PerUserRoamingAndLocal);
}
catch (ConfigurationErrorsException ex)
{
    string filename = ex.Filename;
    _logger.Error(ex, "Cannot open config file");

    if (File.Exists(filename) == true)
    {
        _logger.Error("Config file {0} content:\n{1}", filename, File.ReadAllText(filename));
        File.Delete(filename);
        _logger.Error("Config file deleted");
        Properties.Settings.Default.Upgrade();
        // Properties.Settings.Default.Reload();
        // you could optionally restart the app instead
    }
    else
    {
        _logger.Error("Config file {0} does not exist", filename);
    }
}

It will restore the user.config using the Properties.Settings.Default.Upgrade(); again without null values.