根据日期算出天数

//计算天数
protected int getDays(DateTime date1, DateTime date2)
{

int days = 0;
if (date1.Year == date2.Year)
{
if (date1.Month < date2.Month)
{
days = (date2.Day - date1.Day) + (date2.Month - date1.Month) * 30;
}
if (date2.Month == date1.Month)
{
days = date2.Day - date1.Day;
}
}
else
{
DateTime date3 = Convert.ToDateTime(date1.Year + "- 12 - 31");
DateTime date4 = Convert.ToDateTime(date2.Year + "- 01 - 01");
int day1 = 0;
if (date1.Month < date3.Month)
{
day1 = (date3.Day - date1.Day) + (date3.Month - date1.Month) * 30;
}
if (date3.Month == date1.Month)
{
day1 = date3.Day - date1.Day;
}

int day2 = 0;
if (date4.Month < date2.Month)
{
day2 = (date2.Day - date4.Day) + (date2.Month - date4.Month) * 30;
}
if (date4.Month == date2.Month)
{
day2 = date2.Day - date4.Day;
}

days = day1 + day2;

}
return days;
}