c# create xml from byte array

XmlDocument doc = new XmlDocument();
string xml = Encoding.UTF8.GetString(buffer);
doc.LoadXml(xml);

OR

XmlDocument doc = new XmlDocument();
MemoryStream ms = new MemoryStream(buffer);
doc.Load(ms);

This assumes your data has UTF8 encoding which is the usual for XML. Also buffer here is the byte array.