求大神帮忙解决日期控件有关问题

求大神帮忙解决日期控件问题
string myStrYear, myStrMonth, myStrDay, myStrDay1;
  string myStrFileName = "";
  myStrYear = myDTTime.Year.ToString().Substring(2, 2);
  if (myDTTime.Month > 9)
  {
  myStrMonth = myDTTime.Month.ToString();
  }
  else
  {
  myStrMonth = "0" + myDTTime.Month.ToString();
  }
  if (myDTTime.Day > 9)
  {
  myStrDay = myDTTime.Day.ToString();
  }
  else
  {
  myStrDay = "0" + myDTTime.Day.ToString();
  }
  d = Convert.ToInt32(myStrDay) - 1;
  myStrDay1 = Convert.ToString(d);

  myStrFileName = myStrYear + myStrMonth + myStrDay1 ;

[解决办法]
比如：

C# code

DateTime tody = DateTime.Now;DateTime yesdy = tody.AddDays(-1);Console.WriteLine(yesdy.ToString());
[解决办法]
探讨

比如：

C# code

DateTime tody = DateTime.Now;
DateTime yesdy = tody.AddDays(-1);
Console.WriteLine(yesdy.ToString());

[解决办法]
探讨


比如：
C# code

DateTime tody = DateTime.Now;
DateTime yesdy = tody.AddDays(-1);
Console.WriteLine(yesdy.ToString());

[解决办法]
[code=C#][/code]

DateTime dt=DateTime.Now;
//前一天  
dt.AddDays(-1);
//前一周  
dt.AddDays(-7);
//前一月  
dt.AddMonths(-1);
//前一年  
dt.AddYears(-1);