Question

我想询问我的客户，他们的生日还未到来。

我已经尝试过这个查询，当然 - 它已经失败了：

Addresses.Where(adr => adr.DateOfBirth != null && adr.DateOfBirth.Value >
DateTime.Now).Take(15).ToList();

当然这不能正常工作（如果你将来出生的话），我想知道如何在没有一年的情况下查询我的Nullable<DateTime>？

Answer 1

你可以这样做一行：

context.Addresses.Where(adr => adr.DateOfBirth != null).OrderBy(adr => EntityFunctions.DiffDays(DateTime.Today, EntityFunctions.AddYears(adr.DateOfBirth, EntityFunctions.DiffYears(adr.DateOfBirth, DateTime.Today) + ((adr.DateOfBirth.Month < DateTime.Today.Month || (adr.DateOfBirth.Day <= DateTime.Today.Day && adr.DateOfBirth.Month == DateTime.Today.Month)) ? 1 : 0)))).Take(15).ToList();

或者以更易读的格式：

var query = from adr in context.Addresses
            where adr.DateOfBirth != null
            let diffYears = EntityFunctions.DiffYears(adr.DateOfBirth, DateTime.Today)
            let birthdayOccurred = adr.DateOfBirth.Month < DateTime.Today.Month || (adr.DateOfBirth.Day <= DateTime.Today.Day && adr.DateOfBirth.Month == DateTime.Today.Month)
            let nextBirthdate = EntityFunctions.AddYears(adr.DateOfBirth, diffYears + (birthdayOccurred ? 1 : 0))
            let daysToBirthdate = EntityFunctions.DiffDays(DateTime.Today, nextBirthdate)
            orderby daysToBirthdate
            select adr;

var result = query.Take(15).ToList();

Answer 2

尝试这样的事情; （这是有效的 - 我已经测试过了）

//A mock up value for comparison (as DayOfYear not supported in Linq)
int doy = DateTime.Today.Month * 31 + DateTime.Today.Day;

var results = Addresses.Where(a => a.DateOfBirth != null)
             .OrderBy( a => 
             (a.DateOfBirth.Value.Month * 31 + a.DateOfBirth.Value.Day) +
  (a.DateOfBirth.Value.Month * 31 + a.DateOfBirth.Value.Day > doy ? 0 : 400 ))
             .Take(15).ToList();

Answer 3

我不确定你能否做到这一点。当然没有任何清晰度。

所需的步骤是：

创建一个仅包含生日的有序列表月/日来到今天。
创建一个有序列表，其中仅包含当月之前的月/日的生日。
将第二个列表附加到第一个列表，您现在有一个列表，已排序生日订单。
取第15个。

我认为C＃代码看起来像这样（你可能需要添加一两个List。）

var list1 = Addresses.Where(adr => adr.DateOfBirth != null && (adr.DateOfBirth.Value.Month > DateTime.Today.Month || (adr.DateOfBirth.Value.Month == DateTime.Today.Month && adr.DateOfBirth.Value.Day >= DateTime.Today.Day))).ToList();
var list2 = Addresses.Where(adr => adr.DateOfBirth != null && (adr.DateOfBirth.Value.Month < DateTime.Today.Month || (adr.DateOfBirth.Value.Month == DateTime.Today.Month && adr.DateOfBirth.Value.Day < DateTime.Today.Day))).ToList();
var fullList = list1.Add(list2);

Answer 4

我不熟悉Linq，我会尝试帮助一些伪代码。

最重要的条件应如下所示：

Date(CurrentDate.Year, DateOfBirth.Month, DateOfBirth.Day) >= CurrentDate 
|| ' OR
Date(CurrentDate.Year + 1, DateOfBirth.Month, DateOfBirth.Day) >= CurrentDate

这也将在12月31日开始。

替代：

// consider this as pseudocode, I didnt tested that in C#

function GetNextBirthday(DateTime DateOfBirth)
{
int yearOfNextBirthday;

int birthdayMMDD = DateOfBirth.Month*100 + DateOfBirth.Day;
int todayMMDD = CurrentDate.Month*100 + CurrentDate.Day;

    if (birthdayMMDD >= todayMMDD)
    {
        yearOfNextBirthday = CurrentDate.Year; // this year
    }
    else
    {
        yearOfNextBirthday = CurrentDate.Year + 1; // next year
    }

DateTime nextBirthday; 

// you have to write this line yourself, i dont remember how to make date from Y, M, D
nextBirthday = DateFromYMD(yearOfNextBirthday, DateOfBirth.Month, DateOfBirth.Day);

return nextBirthday;
}

Answer 5

这是我的“单线班次”条目：

DateTime now = DateTime.Now;
var next15 =
    from a in db.Addresses
    where a.DateOfBirth != null
    let diff = EntityFunctions.DiffSeconds(
        EntityFunctions.AddYears(now, -EntityFunctions.DiffYears(a.DateOfBirth, now)),
        a.DateOfBirth)
    orderby diff >= 0 ? diff : diff + 366*24*60*60
    select new a;

var res = next15.Take(15).ToList();

刚刚使用SQL数据库进行测试 - 它就像魅力一样;）

Answer 6

这是与@Aducci相同的解决方案，但具有可以为空的日期和DBFunctions，因为EntityFunctions已被弃用。

          pacientes = from paciente in pacientes
                where paciente.Nascimento != null
                let diffYears = DbFunctions.DiffYears(paciente.Nascimento, DateTime.Today)
                let birthdayOccurred = paciente.Nascimento.Value.Month < DateTime.Today.Month 
                || (paciente.Nascimento.Value.Day <= DateTime.Today.Day && paciente.Nascimento.Value.Month == DateTime.Today.Month)
                let nextBirthdate = DbFunctions.AddYears(paciente.Nascimento, diffYears + (birthdayOccurred ? 1 : 0))
                let daysToBirthdate = DbFunctions.DiffDays(DateTime.Today, nextBirthdate)
                orderby daysToBirthdate
                select paciente;

查询即将到来的生日

6 个答案: