Custom OrderBy on a List<T>

Question

I'm trying to figure out the best way to custom sort a List. Lets say that T is a Object with a date(DateTime?) property and a status(string) property.

I have 3 cases...

"Urgent": I want these at the top of the list, no particular order
date = null
status = "Urgent"

"Normal": I want these ordered by date after the Urgent cases
date = any valid date/time
status = "On Time"

"Later": I want these at the bottom of the list, no particular order
date = null
status = "Later"

Any thoughts? Should I use an IQuerable object instead of List? I can always .ToList() the object later to send to my view.

Answer 1

query = query.OrderBy(x =>
  x.Status == "Urgent" ? 1:
  x.Status == "Normal" ? 2:
  3)
  .ThenBy(x => 
  x.Status == "Urgent" ? null:
  x.Status == "Normal" ? x.Date:
  null);

Random musing: Does Ordering belong to the query, or to the class?

Answer 2

不应该太困难，只需使用比较规则使T实现IComparable ，就应该设置。

Answer 3

You will need to provide an implementation of IComparer, and then you can pass it in using the following overload:

public static IOrderedEnumerable<TSource> OrderBy<TSource, TKey>(
    this IEnumerable<TSource> source,
    Func<TSource, TKey> keySelector,
    IComparer<TKey> comparer
)

See: http://msdn.microsoft.com/en-us/library/bb549422.aspx

Answer 4

我认为最简单的方法是使用linq：

itemsList = itemsList.OrderByDescending(ob => ob.status ).ThenBy(ob => ob.date).ToList();

Answer 5

You could just use an extension method:

Something like this...

public static IOrderedEmumerable<MyType> OrderForDisplay (this IEnumerable<MyType> input)
{
  return
    input
    .OrderBy(item => item.Status)
    .ThenByDescending(item => item.Status == 1 ? DateTime.MaxDate : item.date);
}