从没有错误&QUOT一个DbSet 3表返回;不能从该查询&QUOT推断; [英] Returning from a DbSet 3 tables without the error "cannot be inferred from the query"

问题描述

我有3个班。 WorkoutSession，WorkoutSessionExercise和锻炼。

I have 3 classes. WorkoutSession, WorkoutSessionExercise and Exercise.

我想返回WorkoutSession 与的WorkoutSession列表与练习有关。 WorkoutSession有许多WorkoutSessionExercise，而这些人有只练习一个1对1的关系。

I would like to return the WorkoutSession with its list of WorkoutSession with the Exercise related. WorkoutSession has many WorkoutSessionExercise, and these one has only a single 1 to 1 relationship with Exercise.

             var query = from workoutSession in DatabaseContext.SetOwnable<WorkoutSession>()
             from workoutSessionExercises in workoutSession.WorkoutSessionExercises
             from exerciseInfo in workoutSessionExercises.Exercise
             where workoutSession.Id == id
             select workoutSession;

最后一个FROM有错误：类型参数不能从查询推断

The last FROM has the error : The type argument cannot be inferred from the query.

我怎样才能加载这个三级LINQ的深对象要实体？

How can I load this three level deep objects with Linq To Entity?

推荐答案

？请问像这样的工作。

Would something like this work?

DatabaseContext.SetOwnable<WorkoutSession>
    .Include("WorkoutSessionExercises.Exercise")
    .Where(w => w.Id == id);

替代语法：

Alternate syntax:

from workoutSession in DatabaseContext.SetOwnable<WorkoutSession>
    .Include("WorkoutSessionExercises.Exercise")
    where workoutSession.Id == id
    select workoutSession;

这里的关键是，包含法 - 这使您可以表明哪些相关的对象应当水分。

The key here is that Include method - this allows you to indicate which related objects should be hydrated.

修改

试试这个，以绕过基于字符串包括（灵感来自于的LINQ嵌套实体中）：

Try this to get around the string-based includes (inspiration from Linq Nested Entities):

var query = from workoutSession in DatabaseContext.SetOwnable<WorkoutSession>
select new
{
     WorkoutSession,
     WorkoutSessionExercises = from workoutSessionExercise in
        DatabaseContext.SetOwnable<WorkoutSessionExercises>
        select new
        {
            WorkoutExercise = from workoutExercise in
                DatabaseContext.SetOwnable<WorkoutExercise>
                select workoutExercise
        }
};

var results = query.Select(r => r.WorkoutSession).Where(w => w.Id == id);

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