C# Hash complete xml

Question

We are trying to hash a xml file, i already have it working that it hashes the contents of the XML. For which i am using the following code:

        XmlDocument doc = new XmlDocument();
        doc.PreserveWhitespace = true;
        doc.Load(txtFile.Text);

        XmlNodeList list = doc.GetElementsByTagName("Document");

        XmlElement node = (XmlElement)list[0];
        //node.SetAttribute("xmlns:xsi", "http://www.w3.org/2001/XMLSchema-instance");
        string s = node.OuterXml;

        using (MemoryStream msIn = new MemoryStream(Encoding.UTF8.GetBytes(s)))
        {
            XmlDsigC14NTransform t = new XmlDsigC14NTransform(true);
            t.LoadInput(msIn);
            using (var hash = new SHA256Managed())
            {
                byte[] digest = t.GetDigestedOutput(hash);
                txtHash.Text = BitConverter.ToString(digest).Replace("-", String.Empty);
            }
        }

however, this only hashes the contents of the XML. What i need is to hash the complete XML instead of only the contents.

If we only hash the contents, our hash doesnt compare with the control we get.

Answer 1

You can read the file contents without creating a XmlDocument and hash the contents:

var file = File.ReadAllBytes(txtFile.Text);
using (var hash = new SHA256Managed())
{
   byte[] digest = hash.ComputeHash(file);
   txtHash.Text = BitConverter.ToString(digest).Replace("-", String.Empty);
}