Checking Given Number is Polindrome or not?

Public void ChkGivenNumberIsPolindromeOrNot()

{

  bool BL = IsPalindrome(textBox2.Text, StringComparison.OrdinalIgnoreCase);

    if (BL == true)

   {

      MessageBox.Show("This is Polindrome");

   }  

      else

     {

       MessageBox.Show("This is not Polindrome");

   }

 }

public bool IsPalindrome(string str, StringComparison comparisonType)

           {

             bool valid = true;

             int halfway = str.Length / 2;

             int lastIndex = str.Length - 1;

             for (int i = 0; i < halfway; i++)

             {

                 if (!str.Substring(i, 1).Equals(str.Substring(lastIndex - i, 1), comparisonType))

                 {

                    valid = false;

                    break;

                 }

             }

            return valid;

          }