Regex.Split takes 2 strings, an input and a pattern. You are trying to use Regex.Split like its String.Split. Basically your Regex is invalid, probably throwing an exception, and then the parts underneath are not being run.
Instead of using Regex.Split, use String.Split, like:
string url = "sfsdfs/sdfsfs/sdfsfs/sdfsf/";
string[] splits = url.Split('/');
Application["num"] = splits.Length.ToString();
string Url = Page.GetRouteUrl("ITEMs", new { NAME = "MOHAMMAD" });
Response.Redirect(url);