使用linq获取列表项中的日期差异
本文关键字:日期 linq 获取 列表 使用 | 更新日期: 2023-09-27 18:18:57
我有一个约会列表,我想在当前约会开始时间和上次约会结束时间之间做一个差异,以确保没有差异。如果有,添加一个假的约会。
我当前的实现是…
public ObservableCollection<Appointment> FillGaps()
{
var appointments = this.Appointments.OrderByDescending(s => s.EndDate).ToList();
for (int i = 0; i < appointments.Count() - 1; i++)
{
var now = appointments[i];
var previous = appointments[i + 1];
if((now.StartDate.Value - previous.EndDate.Value).Days > 1)
{
// add a new appointment between this period
appointments.Add(new Appointment()
{
StartDate = previous.EndDate.Value.AddDays(1),
EndDate = now.StartDate.Value.AddDays(-1),
IsCurrent = false
});
}
}
return appointments.ToObservableCollection();
}
是否有更好或更通用的方法来做到这一点?
要求……添加ToObservable…
/// <summary>
/// The to observable collection.
/// </summary>
/// <param name="coll">
/// The collection.
/// </param>
/// <typeparam name="T"> Object T
/// </typeparam>
/// <returns>
/// The <see cref="ObservableCollection"/>.
/// </returns>
public static ObservableCollection<T> ToObservableCollection<T>(this IEnumerable<T> coll)
{
var c = new ObservableCollection<T>();
foreach (var e in coll)
{
c.Add(e);
}
return c;
}
Appointment类没有什么特别的。
/// <summary>
/// The Appointment.
/// </summary>
[Serializable]
public class Appointment
{
public Appointment()
{
this.IsFake = false;
}
/// <summary>
/// Gets or sets the start date.
/// </summary>
public DateTime? StartDate { get; set; }
/// <summary>
/// Gets or sets the end date.
/// </summary>
public DateTime? EndDate { get; set; }
/// <summary>
/// Gets or sets the Is Fake
/// </summary>
public bool IsFake { get; set; }
}
如果不知道this.Appointments
属性是如何实现的,或者ToObservableCollection
扩展方法的参数是什么,就很难提出最有效的解决方案。但是,像这样的东西应该可以工作:
private static IEnumerable<Tuple<T, T>> ListPairs<T>(IEnumerable<T> source)
{
using (var enumerator = source.GetEnumerator())
{
if (!enumerator.MoveNext()) yield break;
T previous = enumerator.Current;
while (enumerator.MoveNext())
{
T current = enumerator.Current;
yield return new Tuple<T, T>(previous, current);
previous = current;
}
}
}
public ObservableCollection<Appointment> FillGaps()
{
var gaps = ListPairs(this.Appointments.OrderByDescending(s => s.EndDate))
.Where(pair => (pair.Item1.StartDate.Value - pair.Item2.EndDate.Value).Days > 1)
.Select(pair => new Appointment
{
StartDate = pair.Item2.EndDate.Value.AddDays(1),
EndDate = pair.Item1.StartDate.Value.AddDays(-1),
IsCurrent = false,
});
// NB: Assumes "this.Appointments" is a cheap call;
// Also assumes you don't need the results in any particular order.
return this.Appointments.Concat(gaps).ToObservableCollection();
}