LINQ，带有count和orderby的双重联接

Question

LINQ newbie struggling with a query which would be very easy in regular SQL, but for some reason is causing me serious ache when trying to express in lambda/query.

I have three objects: Organization

public class Organization
{
    public int OrganizationId { get; set; }
    public ICollection<Employee> Employees { get; set; }
}

Employee

public class Employee
{
    public int EmployeeId { get; set; }
    public Organization Organization { get; set; }
    public ICollection<Ticket> Tickets { get; set; }
}

Ticket

public class Ticket
{
    public int TicketId { get; set; }
    public Employee Employee { get; set; }
}

Using LINQ, I need to retrieve an ordered list of Organizations by the number of Tickets they have, as an IQueryable, preferable.

This is what I have come up with so far:

var q = Organizations.Join
                    (
                        Employees,
                        org => org.OrganizationId,
                        emp => emp.Organization.OrganizationId,
                        (org, emp) => new {org, emp}
                    )
                    .Join
                    (
                        Tickets,
                        t => t.emp.EmployeeId,
                        ticket => ticket.Employee.EmployeeId,
                        (t, ticket) => new {t, ticket}
                    )
                    .GroupBy(t => t.t.org.OrganizationId)
                    .Select
                    (
                        t => new { OrganizationId = t.Key, TCount = t.Count() }
                    )
                    .OrderByDescending(t => t.TCount).Dump()

So I have the ID's of the Organizations and the count. How would I go about retrieving the full Organization objects?

Answer 1

您不需要使用join，因为每个类都有集合。

Organizations.OrderByDescending(o => o.Employees.Sum(e => e.Tickets.Count()));