C# windiff

using System.Linq;

string resultFileNameadd = @oldPat + deviceID + "difresultadd.txt";

string resultFileNamedel = @oldPat + deviceID + "difresultdel.txt";

if (File.Exists(resultFileNameadd))

File.Delete(resultFileNameadd);

if (File.Exists(resultFileNamedel))

File.Delete(resultFileNamedel);

File.WriteAllLines(resultFileNameadd, File.ReadAllLines(newfilename,Encoding .Default ).Except(File.ReadAllLines(oldfilename,Encoding .Default )), Encoding.Default);