fix System.OutOfMemoryException when reading large string file to a dataset

[sanjay.vaniya]

DataSet ds = new DataSet();
string pattern = @"(</?)(\w+:)";

//[XMLText] is a string variable containing XML downloaded from a WebServices API.
StringReader sr = new StringReader(Regex.Replace(XMLText, pattern, "$1"));                                           
ds.ReadXml(sr);
return ds;