EF获取特定的相关对象

Question

I have a collection of objects in my EF repository called Territories . A Territory is linked to many Distributions , and each Distribution has one CycleID .

How would I write a query against EF that will grab all the Territory objects and the associated Distributions that belong to a specific Cycle , ignoring any Territories that do not have any qualifying Distributions ?

I'm picturing something like:

return this.entities.Territories
    .Include("Distributions")
    .Include("Reps")
    .Where(e => e.Distributions.Any(d => d.CycleID == CycleID))
    .OrderBy(e => e.TerritoryName)
    .AsEnumerable();

but I'm collecting bad Distributions . I can see what it's doing, but I can't figure out how to make it do what I want.

Answer 1

It seems like you are choosing the wrong entry point to your object graph. Start with what you know (the specific Cycle ) and work back to the items you want to retrieve (the Distributions and Territories ).

var cycle = this.entities.Cycles.Single(c => c.CycleID == cycleID);

return cycle.Include("Distributions")
    .Include("Territories")
    .Include("Territories.Reps");

Depending on how you're using the result, you may want to transform it to Enumerable<Territory>

return cycle.Distributions.SelectMany(d => d.Territories)
    .OrderBy(t => t.TerritoryName)
    .AsEnumerable();

You may have to play around with the Include statements because my EF is a bit rusty.

Answer 2

Try this :

var entities = new TestEntities();
        var cycleId = 1;
        var filteredDistributions = entities.Territories
                                    .Join(entities.Distributions.Where(d => d.CycleId == cycleId),
                                          territory => territory.Id,
                                          distribution => distribution.Territory.Id,
                                          (territory, distribution) => distribution);