Write a C# Sharp program to convert a given string value to a 32-bit signed integer

using System;
namespace exercises {
  class Program {
    static void Main(string[] args) {
      String str1;
      str1 = "123456";
      Console.WriteLine("Original String value: " + str1);
      Console.WriteLine("Convert the said string to integer value:");
      Console.WriteLine(str_to_integer(str1));
	  str1 = "+3456";
      Console.WriteLine("Original String value: " + str1);
      Console.WriteLine("Convert the said string to integer value:");
      Console.WriteLine(str_to_integer(str1));
	  str1 = "-123456";
      Console.WriteLine("Original String value: " + str1);
      Console.WriteLine("Convert the said string to integer value:");
      Console.WriteLine(str_to_integer(str1));
	  str1 = "a1234";
      Console.WriteLine("Original String value: " + str1);
      Console.WriteLine("Convert the said string to integer value:");
      Console.WriteLine(str_to_integer(str1));
	  str1 = "123a456";
      Console.WriteLine("Original String value: " + str1);
      Console.WriteLine("Convert the said string to integer value:");
      Console.WriteLine(str_to_integer(str1));	  		  
    }
    public static int str_to_integer(String str1)
        {
          if (string.IsNullOrWhiteSpace(str1)) { return 0; }
            var flag = false;
            var index_num = 0;
            while (index_num < str1.Length && str1[index_num] == ' ') { index_num++; }
          if (str1[index_num] == '-')
            {
                flag = true;
                index_num++;
            }
          else if (str1[index_num] == '+')
            {
                index_num++;
            }
            var max1 = int.MaxValue / 10;
            var max2 = int.MaxValue % 10;
            var result = 0;
            for (; index_num < str1.Length; index_num++)
            {
                var str_digit = str1[index_num] - '0';
                if (str_digit < 0 || str_digit > 9) { break; }
                if (result > max1 ||
                    (result == max1 && str_digit > max2))
                {
                    return flag ? int.MinValue : int.MaxValue;
                }
                result = result * 10 + str_digit;
            }
            return flag ? -result : result;
        }
  }
}