Error: The XML declaration must be the first node in the document

Question

I am getting \"Unexpected XML declaration. The XML declaration must be the first node in the document, and no white space characters are allowed to appear before it\" error

Answer 1

As the error states, the first five characters of an XML document should be <?xml. No ifs, ands or buts. The comments you have above the opening XML tag are illegal; they must go inside the XML tag (because the comment structure is itself defined by the XML standard and so is meaningless outside the main XML tags).

EDIT: Something like this should be able to rearrange the rows, given the file format from the OP:

var lines = new List<string>();

using (var fileStream = File.Open(xmlFilePath, FileMode.Open, FileAccess.Read))
   using(var reader = new TextReader(fileStream))
   {
      string line;
      while((line = reader.ReadLine()) != null)
         lines.Add(line);
   }   

var i = lines.FindIndex(s=>s.StartsWith("<?xml"));
var xmlLine = lines[i];
lines.RemoveAt(i);
lines.Insert(0,xmlLine);

using (var fileStream = File.Open(xmlFilePath, FileMode.Truncate, FileAccess.Write)
   using(var writer = new TextWriter(fileStream))
   {
      foreach(var line in lines)
         writer.Write(line);

      writer.Flush();
   } 

Answer 2

That is not valid XML.

As the error clearly states, the XML declaration (<?xml ... ?>) must come first.

Answer 3

Don't put any comments in the beginning of your file!

Answer 4

I'm using the following function to remove whitespace from xml:

public static void DoRemovespace(string strFile)
    {
        string str = System.IO.File.ReadAllText(strFile);
        str = str.Replace("\n", "");
        str = str.Replace("\r", "");
        Regex regex = new Regex(@">\s*<");
        string cleanedXml = regex.Replace(str, "><");
        System.IO.File.WriteAllText(strFile, cleanedXml);

    }