string startText = "\n\t\\select id \n from ec..... singleQuot;\n S singleQuot;..... \n\\s end";  // \s --> ???
            string[] parts = startText .Split(new string[] {"singleQuot"}, StringSplitOptions.RemoveEmptyEntries );

            // edit only parts "outer" of the separator, this is obtained with step of 2
            for(int x=0; x<parts.Length; x+=2)
            {
                // remove chars: forse questa parte può essere fatta usando una regular expression
                parts[x] = parts[x].Replace("\n", "").Replace("\t", "");
            }

            string finalText= string.Join("singleQuot", parts);