关于日期交集的问题

[GZ2008422]

DateTime ddd;
DateTime dtm=dateTimePicker1.Value;
for (ddd = dtm; ddd < dateTimePicker2.Value; ddd.AddDays(1))//为什么ddd.AddDays(1)不能让日期天数加一天呢?应该怎么弄呢？
{
  int weeks = Convert.ToInt32(ddd.DayOfWeek);
  SetCheckBoxEnable(weeks.ToString().Trim());
}

[GZ2008422]

已经搞定了 ddd=ddd.AddDays(1）

[T3p0]

明显