Using Entity Framework Core, I would like to get a list of the 10 most recently viewed jobs by a user.
I am working on a CRM which contains User, Job and UserJobView classes.
public class User
{
public Guid Id { get; set; }
public string Name { get; set; }
}
public class Job
{
public Guid Id { get; set; }
public string Title { get; set; }
public string Content { get; set; }
}
public class UserJobView
{
public Guid Id { get; set; }
public Guid JobId { get; set; }
public Guid UserId { get; set; }
public DateTime LastViewedAt { get; set; }
public Job Job { get; set; }
}
I also have a JobDto which I project to using AutoMapper
public class JobDto : IMapFrom<Job>
{
public Guid Id { get; set; }
public string Title { get; set; }
public string Content { get; set; }
public DateTime? LastViewedAt { get; set; }
}
Each time a User views a Job I either update or create a UserJobView object setting the LastViewedAt property to be DateTime.Now
I can get the latest viewed items with the following fluent query
return await _context.UserJobViews
.Where(x => x.UserId == thisUserId)
.OrderByDescending(x => x.LastViewed)
.Take(10)
.Select(x => x.Job)
.ProjectTo<JobDto>(_mapper.ConfigurationProvider)
.ToListAsync();
However this obviously doesn't populate the LastViewedAt property for the JobDto. How might I go about doing this?
With a small addition to your configuration, you can make it happen:
CreateMap<UserJobView, JobDto>().IncludeMembers(s => s.Job);
Related
I'm creating an API for an app. The DbContext I have trouble with looks like this:
public class SchoolPlannerDbContext : DbContext
{
public SchoolPlannerDbContext(DbContextOptions<SchoolPlannerDbContext> options) : base(options) { }
public DbSet<Activity> Activities { get; set; }
public DbSet<Room> Rooms { get; set; }
public DbSet<Subject> Subjects { get; set; }
public DbSet<Teacher> Teachers { get; set; }
public DbSet<Group> Groups { get; set; }
}
The Activity class is as follows:
public class Activity
{
public int ID { get; set; }
[Required]
public Teacher Teacher { get; set; }
[Required]
public Room Room { get; set; }
[Required]
public Subject Subject { get; set; }
[Required]
public Group Group { get; set; }
[Required]
public int Slot { get; set; }
[Required]
public int Day { get; set; }
}
All the other properties contain an int ID and a string Name.
My controller looks like this:
public class SqlPlannerData : ISchoolPlannerData
{
private readonly SchoolPlannerDbContext db;
public SqlPlannerData(SchoolPlannerDbContext db)
{
this.db = db;
}
public IEnumerable<Activity> GetActivities()
{
return db.Activities;
}
public IEnumerable<Group> GetGroups()
{
return db.Groups;
}
}
GetGroups() works as intended and returns an IEnumerable with properties set correctly.
My problem is that when I'm trying to access db.Activities, the properties of type, say, Teacher (non-basic types like int) are set to null:
Debugger screenshot.
However, there is a row in the database that looks like this. I.e. the columns exist in the database.
What do I do to make GetActivities() return an IEnumerable with correctly set properties?
Some properties are null because of lazy loading you need to include them
return db.Activities
.Include(i => i.Teacher)
.Include(i => i.Room)
.Include(i => i.Subject)
.Include(i => i.Group)
.ToList()
Each propety Id can be configured by EF5+ as shadows. But I usually prefer to add all Ids explicitely. This way I have much less problem when I am using db context in the project. But is is optional and you can leave it as is
public class Activity
{
public int ID { get; set; }
[Required]
public int? TeacherId { get; set; }
[Required]
public int? RoomId { get; set; }
[Required]
public int? SubjectId { get; set; }
[Required]
public int? GroupId { get; set; }
public virtual Teacher Teacher { get; set; }
public virtual Room Room { get; set; }
public virtual Subject Subject { get; set; }
public virtual Group Group { get; set; }
[Required]
public int Slot { get; set; }
[Required]
public int Day { get; set; }
}
and in order to get list activities you have to add ToList() or ToArray() at least
public IEnumerable<Activity> GetActivities()
{
return db.Activities.ToArray();
}
and by the way, you can' t using not nullabe Id as required becaue it is relevant
[Required]
public int TeacherId { get; set; }
since int by default is 0 and it is a valid value and required will not be working
Is there a better way to load all the related entities?
Below is the ScholarshipRequest class which also has Scholarship, Status, Student, Program and User.
public class ScholarshipRequest
{
public int Id { get; set; }
public int Year { get; set; }
public Status Status { get; set; }
public DateTime ApplicationDate { get; set; }
public DateTime ActionDate { get; set; }
public Scholarship Scholarship { get; set; }
public Program Program { get; set; }
public Student Student { get; set; }
public User User { get; set; }
}
I am just posting Scholarship class here, rest are similar.
public class Scholarship
{
public int Id { get; set; }
public string Name { get; set; }
}
The below code works fine but is there a better way where i can use a single .Include() to load them all or may be some other way?
ScholarshipRequestRepository repo = new ScholarshipRequestRepository(dBContext);
List<ScholarshipRequest> stdList = repo.Collection()
.Include("Status").Include("Student").Include("User").Include("Scholarship")
.Where(x => x.User.Id == userId).ToList();
I'm using EF core, and I have a many-to-many relationship between two entity
IotaProject <--> User
Here's entities & dto related to the question
public class IotaProject
{
[Key]
public int Id { get; set; }
[Required]
public string ProjectName { get; set; }
[Required]
public DateTime Create { get; set; }
public ICollection<ProjectOwnerJoint> Owners { get; set; } = new List<ProjectOwnerJoint>();
}
public class ProjectOwnerJoint
{
public int IotaProjectId { get; set; }
public IotaProject IotaProject { get; set; }
public int UserId { get; set; }
public User User { get; set; }
}
public class User
{
[Key]
public int Id { get; set; }
[Required]
public string FullName { get; set; }
[Required]
public string ShortName { get; set; }
[Required]
public string Email { get; set; }
public ICollection<ProjectOwnerJoint> OwnedProjects { get; set; } = new List<ProjectOwnerJoint>();
}
public class ApplicationDbContext : DbContext
{
public DbSet<IotaProject> IotaProjects { get; set; }
public DbSet<User> Users { get; set; }
public DbSet<ProjectOwnerJoint> ProjectOwnerJoint { get; set; }
}
public class IotaProjectDisplayDto
{
public int Id { get; set; }
public string ProjectName { get; set; }
public DateTime Create { get; set; }
public UserMinDto Owner { get; set; }
public int Count { get; set; }
public IEnumerable<UserMinDto> Reviewers { get; set; }
}
public class UserMinDto
{
public int Id { get; set; }
public string FullName { get; set; }
public string ShortName { get; set; }
}
Following LINQ is the problem, the LINQ purpose is to convert IotaProject to IotaProjectDisplayDto, and key part is that Owners property of IotaProject is ICollection and Owner property in IotaProjectDisplayDto is just one single element UserMinDto, so I only need to get the first element of IotaProject's Owners and that's FirstOrDefault() comes.
IEnumerable<IotaProjectDisplayDto> results = _db.IotaProjects.Select(x => new IotaProjectDisplayDto
{
Id = x.Id,
ProjectName = x.ProjectName,
Create = x.Create,
Owner = x.Owners.Select(y => y.User).Select(z => new UserMinDto { Id = z.Id, FullName = z.FullName, ShortName = z.ShortName }).FirstOrDefault()
});
return results;
it throws run-time exception
Expression of type 'System.Collections.Generic.List`1[ToolHub.Shared.iota.UserMinDto]' cannot be used for parameter
of type 'System.Linq.IQueryable`1[ToolHub.Shared.iota.UserMinDto]'
of method 'ToolHub.Shared.iota.UserMinDto FirstOrDefault[UserMinDto](System.Linq.IQueryable`1[ToolHub.Shared.iota.UserMinDto])' (Parameter 'arg0')
I'm guessing it's probably related to deferred execution, but after read some posts, I still can't resolve it.
Any tips would be appreciated.
Right now, the only way I can get this work is I change type of Owner property in IotaProjectDisplayDto into IEnumrable, which will no longer need FirstOrDefault() to immediate execution. And later on, I manually get the first element in the client to display.
This issue happened in Microsoft.EntityFrameworkCore.SqlServer 3.0.0-preview7.19362.6
I end up downgrade to EF core stable 2.2.6 as Ivan suggested in comment, and everything works fine.
This the table structure I have:
#region Tables
public class WorkoutProfile
{
public WorkoutProfile()
{
WorkoutExercises = new List<WorkoutExercise>();
}
[Key]
public int ProfileId { get; set; }
public string Name { get; set; }
public int Sets { get; set; }
public int RestAfterSetInSeconds { get; set; }
public virtual User User { get; set; }
public virtual ICollection<WorkoutExercise> WorkoutExercises { get; set; }
}
public class WorkoutExercise
{
[Key]
public int WorkoutId { get; set; }
public virtual Exercise Exercise { get; set; }
public int Order { get; set; }
public int WorkoutTimeInSeconds { get; set; }
public int RestAfterInSeconds { get; set; }
}
public class Exercise
{
[Key]
public long ExerciseId { get; set; }
public string Title { get; set; }
public string Visualisation { get; set; }
public bool IsDefault { get; set; } // Is exersice should be included when user first registers
}
public class User
{
[Key]
public long UserId { get; set; }
public string Email { get; set; }
public DateTime Registered { get; set; }
}
#endregion Tables
In the repository class I run the following linq query:
return context
.WorkoutProfiles.Include(w => w.WorkoutExercises)
.Where(q => q.User.UserId == userId && q.ProfileId == profileId)
.FirstOrDefault();
and I receive the good and old "Object reference not set to an instance of an object". When examining the result, see that Exercises property in WorkoutExercises is null.
This is how the database is created using code first approach:
So, the question is: why Exercises not included in WorkoutExercises object? Do I need to include it somehow? I am using .NET Core 2
The simple answer would be no lazy loading in EFCore. Not Released yet but if you want to dabble with alpha code, its in the repository. Based on your classes there are no collections for exercises in WorkoutExcercise.
Then you need to ThenInclude(w => w.Exercises) following your Include clause since EFCore doesn't do lazy loading.
I found a solution following this post
Altered my code as following:
var top = context
.Set<WorkoutProfile>()
.Where(q => q.ProfileId == profileId && q.User.UserId == userId)
.Include(q => q.WorkoutExercises)
.SingleOrDefault();
context
.Entry(top)
.Collection(e => e.WorkoutExercises)
.Query()
.OfType<WorkoutExercise>()
.Include(e => e.Exercise)
.Load();
And it worked
I have a query in EF Core 1.1.2 that is evaluated on client side and would like to know if there is a better way to translate it into sql?
The query:
from l in _ctx.Locations
join i in _ctx.Inventories on l.Id equals i.LocationId
join it in _ctx.Items on i.ItemId equals it.Id
where l.ProjectId == projectid
group i by new {l.Id, l.LHA} into il
select new InventoryLocations() {
Id= il.Key.Id,
LHA = il.Key.LHA,
FlaggedItems = il.Any(x=>x.Item != null && x.Item.Flagged)
}
If not, what other options do I have?
As I know there's still no way mapping views.
FromSQL() method can return types already known in the context only and I can not mark one model as [NotMapped] for example.
Moving back to ef6 is not an option because .net core is the target framework.
Models:
public class Location
{
public Guid Id { get; set; }
[ForeignKey("Project")]
public Guid ProjectId { get; set; }
public Project Project {get; set; }
public string Name { get; set; }
public string LHA { get; set; }
[ForeignKey("ScanUser")]
public Guid? ScanUserId { get; set; }
public User ScanUser { get; set; }
[ForeignKey("CheckUser")]
public Guid? CheckUserId { get; set; }
public User CheckUser { get; set; }
[ForeignKey("GroupLeader")]
public Guid? GroupLeaderId { get; set; }
public User GroupLeader { get; set; }
public int State { get; set; }
}
public class Inventory
{
public Guid Id { get; set; }
[ForeignKey("Project")]
public Guid ProjectId { get; set; }
public Project Project {get; set; }
public string EANCode { get; set; }
[ForeignKey("Location")]
public Guid LocationId { get; set; }
public Location Location { get; set; }
public Double ScanQty { get; set; }
[ForeignKey("ScanUser")]
public Guid? ScanUserId { get; set; }
public User ScanUser { get; set; }
public DateTime? ScanDate { get; set; }
[ForeignKey("Item")]
public Guid? ItemId { get; set; }
public Item Item { get; set; }
[ForeignKey("InventoryTask")]
public Guid? InventoryTaskId { get; set; }
public InventoryTask InventoryTask { get; set; }
[ForeignKey("CheckUser")]
public Guid? CheckUserId { get; set; }
public User CheckUser { get; set; }
public DateTime? CheckDate { get; set; }
public Double PrevQty { get; set; }
}
public class Item
{
public Guid Id { get; set; }
[ForeignKey("Project")]
public Guid ProjectId { get; set; }
public Project Project {get; set; }
public string ItemNo { get; set; }
public string EANCode { get; set; }
public string Name { get; set; }
public Double Price { get; set; }
public bool Deleted { get; set; }
public DateTime ChangeTime { get; set; }
public Double BaseQty { get; set; }
public bool Flagged { get; set; }
}
Currently (and looks like also in the incoming EF Core v.2.0) the GroupBy queries are processed locally, so the key is to avoid them where possible.
And your query seems to be eligible for that - there is no need to first multiply the data set with joins and then group it back.
I've noticed you use only reference navigation properties and FKs in your entities, basically like database table record and SQL. But EF allows you to define also a corresponding collection navigation properties which allow you to start queries from the logical root, thus eliminating the need of joins and group by.
If you define navigation property from Location to Inventory
public class Location
{
// ...
public ICollection<Inventory> Inventories { get; set; }
}
then the equivalent query could be simply:
from loc in _ctx.Locations
where loc.ProjectId == projectid
select new InventoryLocations()
{
Id = loc.Id,
LHA = loc.LHA,
FlaggedItems = loc.Inventories.Any(inv => inv.Item != null && inv.Item.Flagged)
}
which will be fully translated to SQL.
If for some reason you can't create the above collection navigation property, still you can start with locations and manually correlate them with inventories:
from loc in _ctx.Locations
where loc.ProjectId == projectid
select new InventoryLocations()
{
Id = loc.Id,
LHA = loc.LHA,
FlaggedItems = _ctx.Inventories.Any(inv => loc.Id == inv.LocationId && inv.Item != null && inv.Item.Flagged)
}
If you add the navigation property as Ivan correctly suggests:
public class Location
{
// ...
public ICollection<Inventory> Inventories { get; set; }
}
Then you can simply create a query like this:
var locations = _ctx.Locations
.Include(x => x.Inventories)
.ThenInclude(x => x.Item)
.Where(x => x.ProjectId == projectId)
.Select(loc => new InventoryLocations
{
Id = loc.Id,
LHA = loc.LHA,
FlaggedItems = loc.Inventories.Any(inv => inv.LocationId == loc.Id && inv.Item?.Flagged)
});