C# .NET - Extracting only integer part

String format is AS/78AS/1234

  How to extract only 1234(last part) from the above string

var mystring = "AS/78AS/1234";
var lastSlash = mystring.LastIndexOf("/");

if (lastSlash > 0) mystring = mystring.Substring(lastSlash + 1);
System.Diagnostics.Debug.WriteLine(mystring);