[英]NHibernate Criteria query to select the most recent item per type
I need to find the most recent report submitted by members of staff, using an NHibernate criteria query.我需要使用 NHibernate 条件查询查找工作人员提交的最新报告。 I'm sure that I need to use projections, but I can't work out how to set it up.我确定我需要使用投影,但我不知道如何设置它。
A paraphrase of my domain model:我的域 model 的释义:
public class Employee
{
public int Id {get; set;}
public string Name {get; set;}
}
public class Report
{
public int Id {get; set;}
public DateTime? Submitted {get; set;}
public Employee Employee {get; set;}
// Other report properties omitted
}
If there were 5 members of staff, who each have 7 reports, the query should return 5 reports, one per employee, with the Submitted property being not null, and being most recent one for that employee .如果有 5 名员工,每人有 7 份报告,则查询应返回 5 份报告,每位员工一份,提交的属性不是 null,并且是该员工最近的一份。
I am not quite sure about this, but check it out:我不太确定这一点,但请查看:
var rst = session.CreateCriteria<Report>()
.SetProjection(Projections.GroupProperty("Employee"))
.SetProjection(Projections.Max("Submitted"))
.Add(NHibernate.Criterion.Expression.IsNotNull("Submitted")).List();
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