字符串反转

  string str="dsf";
            char [] array1=str.ToCharArray();
            for (int i = 0; i < array1.Length/2;i++ )
            {
                var temp = array1[i];
                array1[i] = array1[array1.Length - 1 - i];

                array1[array1.Length - 1 - i] = temp;
            }
            return new string(array1);