int i=(int)DateTime.Today.DayOfWeek;
switch(i)
{
case 0:
txtDate.Text="星期天";
break;
case 1:
txtDate.Text="星期一";
break;
case 2:
txtDate.Text="星期二";
break;
case 3:
txtDate.Text="星期三";
break;
case 4:
txtDate.Text="星期四";
break;
case 5:
txtDate.Text="星期五";
break;
……………………