DateTime 的 ToString 并没有格式化星期这一东西。

　　网上说这么用：

　　System.Globalization.CultureInfo.CurrentCulture.DateTimeFormat.GetDayName(DateTime.Now.DayOfWeek)

　　上面显示计算机当前设置的星期，受控制面板中“区域和语言选项”的影响。若要显示特定区域和语言的星期，可使用下面的代码：

　　System.Globalization.CultureInfo.GetCultureInfo("zh-CN").DateTimeFormat.GetDayName(DateTime.Now.DayOfWeek)

　　当然，如果觉得不放心，还有另外一种方法，也就是自己写方法：

protected void Page_Load(object sender, EventArgs e)
{
_result.Text = "今天是：" + DateTime.Now.ToString("yyyy年MM月dd日") + " " + GetDayName();
}

private string GetDayName()
{
string result = "";

DateTime today = DateTime.Now;
if (today.DayOfWeek == DayOfWeek.Monday)
{
result = "星期一";
}
else if (today.DayOfWeek == DayOfWeek.Tuesday)
{
result = "星期二";
}
else if (today.DayOfWeek == DayOfWeek.Wednesday)
{
result = "星期三";
}
else if (today.DayOfWeek == DayOfWeek.Thursday)
{
result = "星期四";
}
else if (today.DayOfWeek == DayOfWeek.Friday)
{
result = "星期五";
}
else if (today.DayOfWeek == DayOfWeek.Saturday)
{
result = "星期六";
}
else if (today.DayOfWeek == DayOfWeek.Sunday)
{
result = "星期日";
}

return result;
}