There are a number of ways: You could use string methods, or FileInfo methods, depending on what "2222" is:
string path = @"d:\myfolder\myTest\testfolder\111111\2222";
FileInfo fi = new FileInfo(path);
Console.WriteLine(fi.Name);
string last = path.Substring(path.LastIndexOf('\\') + 1);
Console.WriteLine(last);
In fact, both methods produce the same result, and neither of them require the file of even the folder structure / disk to exist. However, the FileInfo method will require the path to be a valid file specification - it will throw an exception if you give it ":D\myfolder\myTest\testfolder\111111\2222" for example.