獲取所選月份和年份的第一天和最後一天？

Question

我在我的WinForm上有2個組合框。

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

如果我選擇月和2017年它應該顯示我是這樣的：

1-wednesday 
2-Thursday 
. 
. 
. 

到最後那個月只有

Answer 1

，你可以做這樣的：

//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")); 
} 

編輯：我忘了DateTime.DaysInMonth，其可用於甚至simplier解決方案：

//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結構存儲一個值，而不是值的範圍。 MinValue和MaxValue是靜態字段，其中保存DateTime結構實例的可能值範圍。這些字段是靜態的，並且與DateTime的特定實例無關。它們與DateTime類型本身有關。

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

參考here