判断年月日的方法

 1     protected string getChangeDay(string month,int  year)
 2     {
 3         if ((month == "01") || (month == "03") || (month == "05") || (month == "07") || (month == "08") || (month == "10") || (month == "12"))
 4         {
 5             return "31";
 6         }
 7         else if (month == "02")
 8         {
 9             if (year % 4 == 0 && year % 100 != 0 || year % 400 == 0)
10             {
11                 return "28";
12             }
13             else { return "29"; }
14         }
15         else
16         {
17             return "30";
18         }
19     }
20     protected void ddlYear_SelectedIndexChanged(object sender, EventArgs e)
21     {
22         getChage();
23     }
24 
25     private void getChage()
26     { 
28         txtCreator.Value = string.Empty;
29         string year = ddlYear.SelectedValue;
30         string month = ddlMonth.SelectedValue;
31         if (!string.IsNullOrEmpty(year))
32         {
33             txtStartDate.Text = year + "-" + month + "-" + "01";
34             txtEndDate.Text = year + "-" + month + "-" + getChangeDay(month, Convert.ToInt32(year));
35         }       
37     }
38     protected void ddlMonth_SelectedIndexChanged(object sender, EventArgs e)
39     {
40         getChage();
41     }