Credit Card Verification Number, C#

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//Rextester.Program.Main is the entry point for your code. Don't change it.
//Compiler version 4.0.30319.17929 for Microsoft (R) .NET Framework 4.5

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text.RegularExpressions;

namespace Rextester
{
    public class Program
    {

public static bool IsValidLuhnn(string val) {
						
			int currentDigit;
			int valSum = 0;
			int currentProcNum = 0; 
			
			for (int i = val.Length-1; i >= 0; i--) {			
				//parse to int the current rightmost digit, if fail return false (not-valid id)
				if(!int.TryParse(val.Substring(i,1), out currentDigit))
					return false ;

currentProcNum = currentDigit << (1 +i & 1);					 				                				
				//summarize the processed digits
				valSum +=  (currentProcNum > 9 ? currentProcNum - 9 : currentProcNum);
   
			}  
			
			// if digits sum is exactly divisible by 10, return true (valid), else false (not-valid)
            // valSum must be greater than zero to avoid validate 0000000...00 value
			return (valSum > 0 && valSum % 10 == 0) ;
		} 
        
        public static bool isValidCreditCardNumber(string cc) {
            // rule #1, must be only numbers
            if (cc.All(Char.IsDigit) == false) {
                return false;
            }
            // rule #2, must have at least 12 and max of 19 digits
            if (12 > cc.Length || cc.Length > 19) {
                return false;
            }
            // rule #3, must pass Luhnn Algorithm
            return IsValidLuhnn(cc);
            
        }
        
        public static void Main(string[] args)
        {
            //Your code goes here
            
            // Valid Credit Card Numbers (REAL)
            Console.WriteLine("5140871155612017 is a " + (isValidCreditCardNumber("5140871155612017") == true ? "" : "IN") + "VALID Credit Card Number!!"); // must be valid
            Console.WriteLine("4282672617783011 is a " + (isValidCreditCardNumber("4282672617783011") == true ? "" : "IN") + "VALID Credit Card Number!!"); // must be valid
            
            // Passed Luhnn check             
            Console.WriteLine("123455 is a  " + (isValidCreditCardNumber("123455") == true ? "" : "IN") + "VALID Credit Card Number!!"); // must be invalid
            Console.WriteLine("1234569 is a  " + (isValidCreditCardNumber("1234569") == true ? "" : "IN") + "VALID Credit Card Number!!"); // must be invalid
            
            // Valid Credit Card Numbers (size) and Invalid Luhnn Numbers
            Console.WriteLine("0000000000000000 is a  " + (isValidCreditCardNumber("0000000000000000") == true ? "" : "IN") + "VALID Credit Card Number!!"); // must be invalid            
            Console.WriteLine("5140871155612016 is a  " + (isValidCreditCardNumber("5140871155612016") == true ? "" : "IN") + "VALID Credit Card Number!!"); // must be invalid
            Console.WriteLine("4282672617783015 is a  " + (isValidCreditCardNumber("4282672617783015") == true ? "" : "IN") + "VALID Credit Card Number!!"); // must be invalid
            
            // Invalid values for CC
            Console.WriteLine("428267261778B015 is a  " + (isValidCreditCardNumber("428267261778B015") == true ? "" : "IN") + "VALID Credit Card Number!!"); // must be invalid
        }
        
       
    }
}

Show compiler warnings [ + ] Show input
Compilation time: 0,19 sec, absolute running time: 0,09 sec, cpu time: 0,06 sec, average memory usage: 12 Mb, average nr of threads: 3