实例365（5）---------DateTime.IsLeapYear 方法判断是否是闰年，DaysInMonth判断一个月有几天，Addday取得前一天的日期GetYesterDay

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Windows.Forms;

namespace GetDays
{
    public partial class Frm_Main : Form
    {
        public Frm_Main()
        {
            InitializeComponent();
        }

        private void btn_Get_Click(object sender, EventArgs e)
        {
            if (DateTime.IsLeapYear(int.Parse(//判断是否为闰年,IsLeapYear返回bool指定的年份是否为闰年的指示
                DateTime.Now.ToString("yyyy"))))
            {
                MessageBox.Show("本年有366天","提示！");//显示天数信息
            }
            else
            {
                MessageBox.Show("本年有365天", "提示！");//显示天数信息
            }
        }
    }
}

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Windows.Forms;

namespace DaysInMonth
{
    public partial class Frm_Main : Form
    {
        public Frm_Main()
        {
            InitializeComponent();
        }

        private void btn_Get_Click(object sender, EventArgs e)
        {
            int P_Count = DateTime.DaysInMonth(//获取本月的天数,返回指定年和月中的天数。
                DateTime.Now.Year, DateTime.Now.Month);
            MessageBox.Show("本月有" +//显示本月的天数
                P_Count.ToString() + "天", "提示！");
        }
    }
}

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Windows.Forms;

namespace GetYesterDay
{
    public partial class Frm_Main : Form
    {
        public Frm_Main()
        {
            InitializeComponent();
        }

        private void btn_GetYesterday_Click(object sender, EventArgs e)
        {
            MessageBox.Show(//显示前一天日期
                "昨天是：" + DateTime.Now.AddDays(-1).
                ToString("yyyy年M月d日"), "提示！");
        }
    }
}