C#正则表达式判断字符串是否包含大小写字母或数字

using System;
using System.Text.RegularExpressions;

namespace RegExApplication
{
    class Program
    {

        static void Main(string[] args)
        {
            string pattern = @"^[0-9]+$";
            string str = "5511";

            if (Regex.IsMatch(str, pattern))
            {
                Console.WriteLine(str+"全是数字");
            }

            //
            string pattern1 = @"^[A-Z]+$";
            string str1 = "ABC";

            if (Regex.IsMatch(str1, pattern1))
            {
                Console.WriteLine(str1 + "全是大写字母");
            }

            //
            string pattern2 = @"^[a-z]+$";
            string str2 = "abc";

            if (Regex.IsMatch(str2, pattern2))
            {
                Console.WriteLine(str2 + "全是小写字母");
            }

            //
            string pattern3 = @"^[A-Za-z0-9]+$";
            string str3 = "abcABC123@#$";

            if (Regex.IsMatch(str3, pattern3))
            {
                Console.WriteLine(str3 + "包含有数字或大小写字母");
            }
            else
            {
                Console.WriteLine(str3 + "不完全是数字、大小写字母");
            }


            Console.ReadKey();
        }
    }
}