C# 統計字符串中大寫字母和小寫字母的個數

static void Main() {
            int count1 = 0;
            int count2 = 0;
            Console.WriteLine("請輸入字符串");
            string str = Convert.ToString(Console.ReadLine());
            char[] chars = str.ToCharArray();
            foreach(char num in chars){
                if(num>='A' && num<='Z'){
                       count1++;
                }else if(num>='a' && num<='z'){
                        count2++;
                }
            }
            Console.WriteLine("大寫個數爲："+count1);
            Console.WriteLine("小寫個數爲：" + count2);
            Console.ReadKey();
        }