Euler Problem 35

Fairly straight forward this one…

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static void Main(string[] args)
        {
            int counter = 0;

            for (long i = 2; i < 1000000; i++)
            {
                string s = i.ToString();
                int l= s.ToString().Length;

                int c = 0;

                for (int x = 0; x <l; x++)
                {
                    string sr = s.Substring(x, l - x) + s.Substring(0,x);
                    if (!isprime(Convert.ToInt32(sr)))
                    {
                        break;
                    }
                    else
                    {
                        c++;
                    }

                }

                if (c==l) {
                    counter++;}

            }

            Console.WriteLine(counter);
            Console.ReadLine();

        }

 

static bool isprime(int n)
       {
           if (n == 2 || n == 3 || n == 5) { return true; }

          if (n%2==0) {return false;}
          if (n%3 == 0) { return false;}
          if (n%5 == 0) { return false;}

          for (int t = 7; t < Math.Sqrt(n); t++)
          {
              if (n % t== 0)
              {
                  return false;
              }
          }

          return true;

       }