.NET中關於顯示星期幾的問題

今天做項目是用到顯示當前日期是星期幾，上網找了一下，找到如下幾個方法：
第一種方法(個人所寫)

DateTime.Now.GetDateTimeFormats('D')[2].ToString().Substring(0,3)

第二種方法

public string Week()
        {
            string[] weekdays ={ "星期日" ,"星期一" ,"星期二" ,"星期三" ,"星期四" ,"星期五" ,"星期六" };
            string week=weekdays[Convert.ToInt32(DateTime.Now.DayOfWeek)];

            return week;
        }

//Response.Write(Week());

第三種方法

public string Week(string weekName)
        {
            string week;
            switch(weekName)
            {
                case "Sunday":
                    week = "星期日";
                    break;
                case "Monday":
                    week = "星期一";
                    break;
                case "Tuesday":
                    week = "星期二";
                    break;
                case "Wednesday":
                    week = "星期三";
                    break;
                case "Thursday":
                    week = "星期四";
                    break;
                case "Friday":
                    week = "星期五";
                    break;
                case "Saturday":
                    week = "星期五";
                    break;
                    return week;
            }
        }

//Response.Write(Week(DateTime.Now.DayOfWeek));

第四種方法

string CaculateWeekDay(int y,int m, int d)
{
 if(m==1) {m=13;y--;}
 if(m==2) {m=14;y--;}
 int week=(d+2*m+3*(m+1)/5+y+y/4-y/100+y/400)%7+1; 
 string weekstr="";
 switch(week)
 {
  case 1: weekstr="星期一"; break;
  case 2: weekstr="星期二"; break;
  case 3: weekstr="星期三"; break;
  case 4: weekstr="星期四"; break;
  case 5: weekstr="星期五"; break;
  case 6: weekstr="星期六"; break;
  case 7: weekstr="星期日"; break;
 }

 return weekstr; 
}