c#基礎功能

using System.Net;

internal class Program
{
    private static void Main(string[] args)
    {
        //組成字符串
        var m1 = string.Concat(1, 2,3,4,121);
        //判斷是否有空格的字符串
        string.IsNullOrWhiteSpace(" ");
        string i1 ="abc";string i2 = "ABC";
        //比較結果0是相等
        int r1 = string.Compare(i1, i2,ignoreCase:true);
        //百分比
        var a = (decimal)5;
        var b = 3;
        var c = (a / b).ToString("p");
        //時間戳轉時間
        var t1 = StampToDateTime("1686037513000");
        //url轉成base64
        var result = GetUrlToBase64(@"http://59.249.230.64:80/group1/M00/9B/66/O_nmQGR-5T2AGYEeAAKraJLaWBc10.jpeg");
        //發佈環境才走
        #if !DEBUG
          var ttt = "ssss";
        #endif
        //分組去每組最大的積分
        var customerList = new List<Customer>{
              new Customer {Name = "a", Score =30},
              new Customer {Name = "a", Score =35},
              new Customer {Name = "b", Score =20},
              new Customer {Name = "c", Score =50},
              new Customer {Name = "b", Score =60},
              new Customer {Name = "a", Score =80},
          };
        List<Customer> customers = customerList .GroupBy(t => t.Name).SelectMany(a => a.Where(b => b.Score == a.Max(c => c.Score))).ToList();
        foreach (var data in customers)
        {
            Console.WriteLine(data.Name + "," + data.Score);
        }
        Console.ReadLine();
    }
    /// <summary>
    /// 獲取網絡圖片轉換爲base64
    /// </summary>
    /// <param name="url">網絡圖片路徑   例：http://123.123.123.123/a.jpg</param>
    /// <returns></returns>
    public static (bool, string) GetUrlToBase64(string url)
    {
        try
        {
            WebClient mywebclient = new WebClient();
            byte[] Bytes = mywebclient.DownloadData(url);
            string Base64string = Convert.ToBase64String(Bytes);
            return (true, Base64string);
        }
        catch (Exception e)
        {
            return (false, null);
        }
    }
    /// <summary>
    /// 時間戳轉時間帶毫秒
    /// </summary>
    /// <param name="timeStamp"></param>
    /// <returns></returns>
    public static DateTime StampToDateTime(string timeStamp)
    {
        DateTime dtStart = TimeZone.CurrentTimeZone.ToLocalTime(new DateTime(1970, 1, 1));
        long lTime = long.Parse(timeStamp + "0000");
        TimeSpan toNow = new TimeSpan(lTime);
        return dtStart.Add(toNow);
    }

}
public class Customer
{
    public string Name;
    public int Score;
}