使用nhibernate，我将如何构造一个想要最近50行的查询

Question

i have a table called orders and i have a column called Last Update (and an order object with a LastUpdate property). I want to construct a query using nhibernate to get the last 50 rows so i don't go to the database and get everything and then have to filter results in my application.

is this possible in nhibernate. I am trying to use the LINQ api

Answer 1

如果您使用的是Criteria，则使用SetMaxResults（50）并对日期时间进行降序排序。

Answer 2

Here's the LINQ version of this query.

var orders = session.Query<Order>()
    .OrderByDescending(x => x.LastUpdate)
    .Take(50);

Here's the screen shot of the code sample...

Here's the screen shot from NHibernate Profiler...

Answer 3

你可以使用SetMaxResults(50) ，虽然取决于你想要的50行（最新？第一？最后？），你可能也需要做一个SortBy表达式。

Answer 4

var orders = session.Query<Linq>()
    .OrderByDescending(x => x.LastUpdate)
    .Take(50);

Answer 5

In general case suggesing LastUdate can be nullable using Linq2SQL you may write extension method to your IQueriable:

public static partial class FooTable
{
    public static IQueryable<FooTable> LastUpdated(this IQueryable<FooTable> queryable, int count)
    {
        return queryable.Where(x => (x.LastUdate != null))
            .OrderByDescending(x => x.LastUdate)
            .Take(count);
    }
}