获取所选月份和年份的第一天和最后一天？

Question

我在我的WinForm上有2个组合框。

combobox1 --> displaying months 
combobox2 --> displaying years 

如果我选择月和2017年它应该显示我是这样的：

1-wednesday 
2-Thursday 
. 
. 
. 

到最后那个月只有

Answer 1

，你可以做这样的：

//clear items 
comboBox1.Items.Clear(); 

int month = 5; 
int year = 2017; 

//new datetime with specified year and month 
DateTime startDate = new DateTime(year, month, 1); 

//from first day of this month until first day of next month 
for (int i = 0; i < (startDate.AddMonths(1) - startDate).Days; i++) 
{ 
    //add one day to start date and add that in "number - short day name" in combobox 
    this.comboBox1.Items.Add(startDate.AddDays(i).ToString("dd - ddd")); 
} 

编辑：我忘了DateTime.DaysInMonth，其可用于甚至simplier解决方案：

//clear items 
comboBox1.Items.Clear(); 

int month = 5; 
int year = 2017; 
//calculate how many days are in specified month 
int daysInMonth = DateTime.DaysInMonth(year, month); 

//loop through all days in month 
for (int i = 1; i <= daysInMonth; i++) 
{ 
    //add one day to start date and add that in "number - short day name" in combobox 
    this.comboBox1.Items.Add(new DateTime(year, month, i).ToString("dd - ddd")); 
} 

Answer 2

DateTime结构存储一个值，而不是值的范围。 MinValue和MaxValue是静态字段，其中保存DateTime结构实例的可能值范围。这些字段是静态的，并且与DateTime的特定实例无关。它们与DateTime类型本身有关。

DateTime date = ... 
var firstDayOfMonth = new DateTime(date.Year, date.Month, 1); 
var lastDayOfMonth = firstDayOfMonth.AddMonths(1).AddDays(-1); 

参考here