I have two simple classes
public class User
{
public User()
{
Roles = new Collection<Role>();
}
public int UserId { get; set; }
public string UserName { get; set; }
public ICollection<Role> Roles { get; set; }
}
public class Role
{
public Role()
{
Users = new Collection<User>();
}
public int RoleId { get; set; }
public string RoleName { get; set; }
public ICollection<User> Users { get; set; }
}
I have seeded it with the following data by overriding the seed method
var firstUser = new User {UserName = "vivekr"};
var secondUser = new User {UserName = "vivekm"};
var firstRole = new Role {RoleName = "admin"};
var secondRole = new Role {RoleName = "user"};
firstUser.Roles.Add(firstRole);
firstUser.Roles.Add(secondRole);
secondUser.Roles.Add(firstRole);
context.Users.Add(firstUser);
context.Users.Add(secondUser);
Mapping is done by overriding OnModelCreating()
protected override void OnModelCreating(DbModelBuilder modelBuilder)
{
modelBuilder.Entity<User>()
.HasMany<Role>(r=> r.Roles)
.WithMany(u => u.Users)
.Map(c=>
{
c.MapLeftKey("UserId");
c.MapRightKey("RoleId");
c.ToTable("UserRoles");
});
}
All tables are created correctly and I can see that the values are correct(including mappings)
But I there are issues when fetching the data
If I do(assuming that db is an instance of my Context class)
var selectedRoles = db.Users.Find(1).Roles;
I get the count of selectedRoles to be 0. It is supposed to be 2. I have no idea why this is happening
you need to use Include(). When you use include you can't use find anymore. Try something like this:
db.Users.Include("Roles ").FirstOrDefault(x => x.UserId == 1).Roles;
Entity framework will not automatically load related objects for you. You have to tell it to do so by eagerly fetching like above or by using lazy load.
Here is a good article that explains different techniques for pulling in related data.
Related
I know many to many relationships are not automatically done in previous versions of EF, but am I forgetting something because I can not retrieve a list.
I have the following data
public class User
{
public int Id { get; set; }
public List<UserGroup> Groups { get; set; }
}
public class UserGroup
{
public int Id { get; set; }
public void AddUser(User user)
{
Users.Add(user);
user.Groups.Add(this);
}
}
When checking the data based I find I have the groups point to the users.
When retrieving the group from the database it is empty (no users)
[HttpGet]
public async Task<IActionResult> GetUsers(int id)
{
var group = (await context.Groups.Include(userGroup => userGroup.Users).SingleAsync(group => group.Id == id));
var users = group.Users;
Console.WriteLine(users.ToArray()); //empty
Console.WriteLine(group.name); // prints group name correctly
return Ok(users.ToArray());
}
I'm a little stumped, did I forget something?
I have next entity
public class Objective
{
public virtual UserInfo AssignedUser { get; set; }
public int? AssignedUserID { get; set; }
public string ObjectiveText { get; set; }
public virtual ICollection<ObjectiveTask> Tasks { get; set; }
public virtual UserInfo User { get; set; }
public int UserID { get; set; }
}
One objective could has one Assigned User and one User but many Tasks.
After getting Entity from DB I map it to DTO class which looks like this
public class ObjectiveListViewModel
{
public string AssignedString { get; set; }
public string ObjectiveText { get; set; }
public int TasksCount { get; set; }
public string UserContactName { get; set; }
}
Mapping settings doesn't meter
When I do this with query like this
(from objective in context.Set<Objective>() select objective)
.Include(o => o.User)
.Include(o => o.AssignedUser)
.ToListAsync();
Everything works cool - User and Assigned User properties are loaded and no need do extra query to DB to get their data.
But I need return objectives with tasks amount.
To do this I've created a generic class
public class EntitySubCount<TEntity>
{
public TEntity Entity { get; set; }
public int GroupCount { get; set; }
}
And use it in this way
(from objective in context.Set<Objective>() select objective)
.Include(o => o.User)
.Include(o => o.AssignedUser)
.Select(o=> new EntitySubCount<Objective> {
Entity = o,
GroupCount = o.Tasks.Count })
.ToListAsync();
But User and Assigned User properties are not loaded and it require additional query to DB to get their data.
I understand that it because lazy loading.
The question is - how I can get from DB my Entity with loaded nav. properties and with count of Tasks at once?
Thank you for any help
You are close. No need for the includes if you are projecting. In this case I project to an anonymous type, but you could create a ViewModel class to project to if desired.
var objectiveList = context.Objectives
.Select(o => new
{
Entity = o,
// or you could just pick the properties:
ObjectiveText = o.ObjectiveText,
User = o.User,
AssignedUser = o.AssignedUser,
GroupCount = o.Tasks.Count
}).ToList();
EDIT: I see you already have a ViewModel(DTO). You might be looking for something like this:
var objectiveList = context.Objectives
.Select(o => new ObjectiveListViewModel
{
AssignedString = o.AssignedUser.Name,
ObjectiveText = o.ObjectiveText,
TasksCount = o.Tasks.Count
UserContactName = o.User.Name
}).ToList();
I have a WCF project and I generate the database with Entity framework v6 and code-first.
But I have a problem with the relation between the class User and FeedRss. I want several FeedRss for each User. My code work (no exception) but don't add in the ICollection feeds (in user), this list is empty after the recovery in the database.
public class User
{
[Key]
public int UserID {get; set;}
...
[InverseProperty("User")]
public ICollection<FeedRSS> feeds { get; set; }
public User()
{
feeds = new List<FeedRSS>();
}
}
one user->many feedRss
public class FeedRSS
{
[Key]
public int ID { get; set; }
...
public int UserId { get; set; }
[ForeignKey("UserId")]
public User User { get; set; }
public FeedRSS()
{
}
}
public class UsersContext : DbContext
{
public DbSet<User> Users { get; set; }
public DbSet<FeedRSS> Feeds { get; set; }
}
My function for test my code (but return a empty list) :
public User getUser(int Id)
{
using (UsersContext context = new UsersContext())
{
return context.Users.ToList().Find(
delegate(User u) {
return u.UserID == Id;
});
}
}
public List<FeedRSS> getFeedListTest(User u)
{
using (UsersContext ctx = new UsersContext())
{
User user = ctx.Users.First(i => i.UserID == u.UserID);
FeedRSS f = new FeedRSS() { name = "code", link = "uri" };
user.feeds.Add(f);
//the list user.feeds lenght is = 1
ctx.SaveChanges();
//update working
}
//get the same user in the database but the list uuu.feeds lenght is 0 :(
User uuu = this.getUser(u.UserID);
return uuu.feeds.ToList();
}
I tested other code very different (fluent API, force the UserId in FeedRss..) but I do not understand the principle of the relation in entity framework... I tried unsuccessfully several examples code...
*And sorry for my approximate English
You can either load feeds with Include(...) statement as CodeNotFound suggested or you can make the feeds collection virtual - that will enable lazy loading and EF will load feeds for you automatically on the fly.
public class User {
...
[InverseProperty("User")]
public virtual ICollection<FeedRSS> feeds { get; set; }
}
You can find a nice article about lazy loading and eager loading on the MSDN portal
I have (2) entities, they are as follows:
[Table("User")]
public class User
{
[Key]
[DatabaseGeneratedAttribute(DatabaseGeneratedOption.Identity)]
public int UserId { get; set; }
[Required]
[MaxLength(20)]
public string Name { get; set; }
public ICollection<Role> Roles { get; set; }
public User()
{
this.Roles = new Collection<Role>();
}
}
[Table("User")]
public class Role
{
[Key]
[DatabaseGeneratedAttribute(DatabaseGeneratedOption.Identity)]
public int RoleId{ get; set; }
[Required]
[MaxLength(20)]
public string Name { get; set; }
public ICollection<User> Users { get; set; }
public Role()
{
this.Users = new Collection<User>();
}
}
This creates three tables in my database, User, Role and UserRole.
I am leveraging a generic repository, my Add and Update look like the following:
public virtual void Add(TEntity entity)
{
_dbSet.Add(entity);
}
public virtual void Update(TEntity entity)
{
_dbSet.Attach(entity);
_dbContext.Entry(entity).State = EntityState.Modified;
}
If I want to add a new User with Roles, I have to do the following in my UserRepository, which inherits from my generic repository.
public override void Add(User entity)
{
foreach (var role in entity.Roles)
_dbContext.Roles.Attach(role);
base.Add(entity);
}
This seems clunky, but it works.
My trouble is now when I want to update a User, say add a new Role. I thought I could do something similar.
public override void Update(User entity)
{
foreach (var role in entity.Roles)
_dbContext.Roles.Attach(role);
base.Update(entity);
}
But this does not work ... any ideas on what I am doing wrong would be appreciated!
Update
My use case is I have an existing User with X Roles, I add Y number of Roles, I want to update the User with the Y number of new Roles.
You shouldn't need to do that. If the role does not yet exist, you would do something like this:
var user = new User { Name="Fred" }
user.Roles.Add(new Role { Name="Accounting" });
context.Add(user);
If you are adding an existing role, then you need to get that role first
var role = context.Roles.Single(x => x.Name="Accounting");
var user = new User { Name="Fred" }
user.Roles.Add(role);
context.Add(user);
I have two objects (WishListItem and Product) in a one-to-many relationship. WishListItem has to have a product. Each Product can be in 0 - n WishListItems.
public class WishListItem
{
public int Id { get; set; }
public int ProductId { get; set; }
public Product Product { get; set; }
}
public class Product
{
public int Id { get; set; }
// ... other properties
}
The Product has no knowledge of WishListItems. All of the Products exist. I just want to add a new WishListItem. My WishListItem model for the relationship is this:
HasRequired(p => p.Product).WithMany().HasForeignKey(p => p.ProductId);
When I try to add a new item like this:
WishListItem item = new WishListItem();
// ... sets properties
WishListItems.Add(item); // WishListItems is of type DbSet<WishListItem>
SaveChanges();
This code seems to try to also add a Product. I don't want to add a new Product (or even update it). The Product property is set to null. How do I tell Entity Framework that I only want to add the WishListItem? Do I need to Ignore the Product property (by doing Ignore(p => p.Product); in my WishListItem model) and load the Product separately whenever I load my WishListItem objects?
I have solved my issue. The problem came from another property on the Product object.
private bool _isFreeShippingInitialValue;
public bool IsFreeShipping
{
get
{
return _isFreeShippingInitialValue ||
computedValueFromAnotherChildObject;
}
set
{
_isFreeShippingInitialValue = value;
}
}
We noticed that when you first get the Product object, the IsFreeShipping.get is called (not sure why) before any child objects are loaded. For example, if _isFreeShippingInitialValue is false and computedValueFromAnotherChildObject is true, IsFreeShipping first returns false (because computedValueFromAnotherChildObject is first false since no child objects have been loaded), then true the next time you try to get IsFreeShipping. This makes EF think the value has changed.
The first item we added to WishListItems worked fine. It was the second item that broke. We believe SaveChanges() (or something prior to it) loaded the Product for the first WishListItem. The SaveChanges() was breaking on the Product of the first WishListItem when we were adding the second item.
So, in short, be careful when computing values in a Property.get using child objects because it can bite you in the butt.
This works for me without adding any new Addresses records. In this model, Person has an optional home address, but address doesn't have any knowledge of the person.
public class Person
{
public int Id { get; set; }
public string FirstName { get; set; }
public string LastName { get; set; }
public virtual Address HomeAddress { get; set; }
public int HomeAddress_id { get; set; }
}
public class Address
{
public int Id { get; set; }
public string PhoneNumber { get; set; }
public string Street { get; set; }
public string City { get; set; }
public string State { get; set; }
public string Country { get; set; }
}
In the DbContext override, I have the below code
protected override void OnModelCreating(DbModelBuilder modelBuilder)
{
modelBuilder.Entity<Person>()
.HasRequired(t => t.HomeAddress).WithMany()
.HasForeignKey(t => t.HomeAddress_id);
}
I can write a unit test like this.
var addressId = 0;
using (var db = new DataContext())
{
var address = new Address { City = "test", Country = "test", PhoneNumber = "test", State = "test", Street = "test" };
db.Addresses.Add(address);
db.SaveChanges();
addressId = address.Id;
}
using (var db = new DataContext())
{
var person = new Person { Email = "test#test.com", FirstName = "Testy", LastName = "Tester", HomeAddress_id = addressId };
db.Persons.Add(person);
db.SaveChanges();
}