I use entity framework and have a set of users:
public class DbModel : DbContext
{
public DbSet<User> Users { get; set; }
I add a User like so:
User UserOne = new User();
model.Users.Add( UserOne );
I request the users count:
int userCount = model.Users.Count();
userCount is "0" I would expect "1". Adding DetectChanges doen't help.
After "model.SaveChanges()" the Count = 1, but that is to late I need to combine the in memory stuff with the DB stuff for validation. Is there a way to do this?
SOLUTION
Using the answer of Erik Philips I wrote the following extension method for the DbSet
public static class DBSetExtentions
{
public static IEnumerable<T> AllMembers<T>(
this DbSet<T> target,
Func<T, bool> selection
) where T : class
{
return target.Local.Where(selection).Union(target.Where(selection));
}
}
it allows me to do selections an validations accross all entities like:
private void ValidateEmail(ValidationDto validationDto)
{
int usersWithSameEmail =
validationDto.Model.Users.AllMembers(
x => x.EmailAddress.Equals( EmailAddress ) ).Count();
if (usersWithSameEmail > 1)
{
validationDto.Result.Add(new ValidationResult("Email address is in use"));
}
}
You can query the client side of items (committed and uncomitted) to your data storage by using Local.
var count = model.Users.Local.Count();
One caveat is that this is only the local representation of Users. Meaning it could contain a partial amount of users from the database (changed and/or unchanged), and new users you've created and not saved.
Interesting Article - Using DbContext in EF 4.1 Part 7: Local Data
Related
I'm using the latest version of ABP from abp.io and have two entities with a many-many relationship. These are:
public class GroupDto : AuditedEntityDto<Guid>
{
public GroupDto()
{
this.Students = new HashSet<Students.StudentDto>();
}
public string Name { get; set; }
public bool IsActive { get; set; }
public virtual ICollection<Students.StudentDto> Students { get; set; }
}
and
public class StudentDto : AuditedEntityDto<Guid>
{
public StudentDto()
{
this.Groups = new HashSet<Groups.GroupDto>();
}
public string Name { get; set; }
public bool IsActive { get; set; }
public virtual ICollection<Groups.GroupDto> Groups { get; set; }
}
I set up the following test to check that I am retrieving the related entities, and unfortunately the Students property is always empty.
public async Task Should_Get_List_Of_Groups()
{
//Act
var result = await _groupAppService.GetListAsync(
new PagedAndSortedResultRequestDto()
);
//Assert
result.TotalCount.ShouldBeGreaterThan(0);
result.Items.ShouldContain(g => g.Name == "13Ck" && g.Students.Any(s => s.Name == "Michael Studentman"));
}
The same is true of the equivalent test for a List of Students, the Groups property is always empty.
I found one single related answer for abp.io (which is not the same as ABP, it's a newer/different framework) https://stackoverflow.com/a/62913782/7801941 but unfortunately when I add an equivalent to my StudentAppService I get the error -
CS1061 'IRepository<Student, Guid>' does not contain a definition for
'Include' and no accessible extension method 'Include' accepting a
first argument of type 'IRepository<Student, Guid>' could be found
(are you missing a using directive or an assembly reference?)
The code for this is below, and the error is being thrown on the line that begins .Include
public class StudentAppService :
CrudAppService<
Student, //The Student entity
StudentDto, //Used to show students
Guid, //Primary key of the student entity
PagedAndSortedResultRequestDto, //Used for paging/sorting
CreateUpdateStudentDto>, //Used to create/update a student
IStudentAppService //implement the IStudentAppService
{
private readonly IRepository<Students.Student, Guid> _studentRepository;
public StudentAppService(IRepository<Student, Guid> repository)
: base(repository)
{
_studentRepository = repository;
}
protected override IQueryable<Student> CreateFilteredQuery(PagedAndSortedResultRequestDto input)
{
return _studentRepository
.Include(s => s.Groups);
}
}
This implements this interface
public interface IStudentAppService :
ICrudAppService< // Defines CRUD methods
StudentDto, // Used to show students
Guid, // Primary key of the student entity
PagedAndSortedResultRequestDto, // Used for paging/sorting
CreateUpdateStudentDto> // Used to create/update a student
{
//
}
Can anyone shed any light on how I should be accessing the related entities using the AppServices?
Edit: Thank you to those who have responded. To clarify, I am looking for a solution/explanation for how to access entities that have a many-many relationship using the AppService, not the repository.
To aid with this, I have uploaded a zip file of my whole source code, along with many of the changes I've tried in order to get this to work, here.
You can lazy load, eagerly load or configure default behaviour for the entity for sub-collections.
Default configuration:
Configure<AbpEntityOptions>(options =>
{
options.Entity<Student>(studentOptions =>
{
studentOptions.DefaultWithDetailsFunc = query => query.Include(o => o.Groups);
});
});
Eager Load:
//Get a IQueryable<T> by including sub collections
var queryable = await _studentRepository.WithDetailsAsync(x => x.Groups);
//Apply additional LINQ extension methods
var query = queryable.Where(x => x.Id == id);
//Execute the query and get the result
var student = await AsyncExecuter.FirstOrDefaultAsync(query);
Or Lazy Load:
var student = await _studentRepository.GetAsync(id, includeDetails: false);
//student.Groups is empty on this stage
await _studentRepository.EnsureCollectionLoadedAsync(student, x => x.Groups);
//student.Groups is filled now
You can check docs for more information.
Edit:
You may have forgotten to add default repositories like:
services.AddAbpDbContext<MyDbContext>(options =>
{
options.AddDefaultRepositories();
});
Though I would like to suggest you to use custom repositories like
IStudentRepository:IRepository<Student,Guid>
So that you can scale your repository much better.
I have a Survey that contains questions and also which users can/will participate in the survey.
like so
public virtual ICollection<User> ParticipatingUsers { get; set; }
public virtual ICollection<Question> SpecificQuestions { get; set; }
However, due to the ajaxy solution I create the questions first and then simply send in the ID of my created question with the survey data. So all I need to do is change the sortingIndex of the question and then add a reference to it in my Survey.
When it comes to users they belong to a Company entity and I only want to reference them from the survey not own them.
But currently I get all the id's for questions and users in my action method (.net mvc) and so currently I load all questions and users and attach them to my survey entity before sending the survey to the repository.
But when my Repository calls Add on dbset it clones the user and question data instead of simply referencing existing data.
I am lost, I have solved this exact problem for a normal navigation property by adding [Foreignkey] but i don't know how that would work with ICollection
For completeness
Here is my action method recieving the data
[HttpPost]
[FlexAuthorize(Roles = "RootAdmin")]
public ActionResult SaveSurvey(EditSurveyViewModel editModel)
{
if (!ModelState.IsValid)
{
//We dont bother to send this in so we need to fetch the list again
editModel.CompanyList = _companyRepository.GetAll();
List<string> deletionList = new List<string>();
//We clear out all questions from the state as we have custom logic to rerender them with the correct values
foreach (var modelstateItem in ModelState)
{
if (modelstateItem.Key.StartsWith("Questions"))
{
deletionList.Add(modelstateItem.Key);
}
}
foreach (string key in deletionList)
{
ModelState.Remove(key);
}
return View("EditSurvey", editModel);
}
List<Question> questionlist = new List<Question>();
int sort = 1;
Question q;
//We have questions sent in from the ui/client
if (editModel.Questions != null)
{
//Go trough each questions sent in
foreach (var question in editModel.Questions)
{
//if it's a page break, just assign our new question the sent in one and set sort index
if (question.IsPageBreak)
{
q = question;
q.SortIndex = sort;
}
else
{
//It's a question and all questions are already created with ajax from the client
//So we simply find the question and then set sort index and tie it to our survey
q = _questionRepository.GetById(question.Id);
q.SortIndex = sort;
}
questionlist.Add(q);
sort++;
}
}
//assign the new sorted questions to our Survey
editModel.Item.SpecificQuestions = questionlist;
List<User> userlist = new List<User>();
foreach (int id in editModel.SelectedUsers)
{
userlist.Add(_userRepository.GetById(id));
}
editModel.Item.ParticipatingUsers = userlist.ToList();
_surveyRepository.SaveSurveyBindAndSortQuestionsLinkUsers(editModel.Item);
return RedirectToAction("Index");
}
Here is the viewmodel the method gets sent in
public class EditSurveyViewModel
{
public Survey Item { get; set; }
public IEnumerable<Question> Questions { get; set; }
public bool FullyEditable { get; set; }
public IEnumerable<Company> CompanyList { get; set; }
public IEnumerable<int> SelectedUsers { get; set; }
}
Finally here is the repo method (so far i only implemented insert, not update)
public void SaveSurveyBindAndSortQuestionsLinkUsers(Survey item)
{
if (item.Id == 0)
{
Add(item);
}
ActiveContext.SaveChanges();
}
Update/Edit
Moho: You are of course correct, I think to my shame I was testing some things and forgot to reset the method before pasting it in here.
I have updated the action method above.
Slauma: Sorry for lack of details, here comes more.
All my repositories look like this
public class EFSurveyRepository : Repository<Survey>, ISurveyRepository
So they inherit a generic repository and implement an interface
The generic repository (the part we use in code above, looks like this)
public abstract class Repository<T> : IRepository<T> where T : class
{
public EFDbContext ActiveContext { get; private set; }
private readonly IDbSet<T> dbset;
public Repository()
{
this.ActiveContext = new EFDbContext("SurveyConnection");
dbset = ActiveContext.Set<T>();
}
public virtual void Add(T entity)
{
dbset.Add(entity);
}
public virtual T GetById(int id)
{
return dbset.Find(id);
}
I have noticed in the database that my User table (for User entity) now contains a Survey_Id field which i do not want it to have. I want a many-to-many where many surveys can link to many users (the same users) but the users should entity-wise still only belong to a Department in a Company.
Also, right now when I run the code (after I corrected my action method) I get the following error:
An entity object cannot be referenced by multiple instances of IEntityChangeTracker.
No InnerException, only that when i try to add the new survey.
The problem is that you are using separate contexts per repository:
public Repository()
{
this.ActiveContext = new EFDbContext("SurveyConnection");
//...
}
In your POST action you have four repositories in place: _companyRepository, _questionRepository, _userRepository and _surveyRepository. It means you are working with four different contexts, i.e. you load data from different contexts, create relationships between entities that are attached to different contexts and save the data in yet another context.
That's the reason for the entity duplication in the database, for the "multiple instances of IEntityChangeTracker" exception and will be the source for many other problems you might encounter in future.
You must refactor the architecture so that you are using only one and the same context instance ("unit of work") in every repository, for example by injecting it into the constructor instead of creating a new one:
private readonly EFDbContext _activeContext;
private readonly IDbSet<T> _dbset;
public Repository(EFDbContext activeContext)
{
_activeContext = activeContext;
_dbset = activeContext.Set<T>();
}
You build up questionList, set it to editModel.Item.SpecificQuestions, then overwrite the reference by settting that same property to editModel.Questions.ToList(), which is from your view model (i.e.: not loaded via your database context like questionList's question objects) and therefore appears to be new questions to your database context,
editModel.Item.SpecificQuestions = questionlist;
// what is this? why?
editModel.Item.SpecificQuestions = editModel.Questions.ToList();
Edit after question update:
Instead of using questionList and assigning to the questions property of the Survey, simply use the property directly.
Also, do you realize that if you're reusing Question records from the DB for multiple Surveys, you're updating the sort order at the question itself and not simply for that Survey? Each time you save a new survey that reuses questions, other surveys' question ordering will me altered. Looks like you need a relationship entity that will map Questions to Surveys where you can also store the sort order so that each survey can reuse question entities without messing up existing surveys question ordering.
Hoping someone could clear things up. In the following ViewModel, does using Entity Framework as my model eliminate the need to use [Model] and [[ViewModelToModel(...)] attributes? The code runs the same with or without them, because the binding in the view ignores them and binds to the ObservableCollection.
Comments?
public class MainWindowViewModel : ViewModelBase
{
Models.OneHour_DataEntities ctx;
public MainWindowViewModel()
: base()
{
Save = new Command(OnSaveExecute, OnSaveCanExecute);
ctx = new Models.OneHour_DataEntities();
Customers = new ObservableCollection<Models.Customer>(ctx.Customers);
}
public ObservableCollection<Models.Customer> Customers
{
get { return GetValue<ObservableCollection<Models.Customer>>(CustomersProperty); }
set { SetValue(CustomersProperty, value); }
}
public static readonly PropertyData CustomersProperty = RegisterProperty("Customers", typeof(ObservableCollection<Models.Customer>), null);
public Command Save { get; private set; }
private bool OnSaveCanExecute()
{
return true;
}
private void OnSaveExecute()
{
ctx.SaveChanges();
}
}
Catel uses different interfaces to take advantage of the models. For example, it uses the following interfaces:
IEditableObject => undoing changes to model when user cancels
INotifyPropertyChanged => update view model when model updates
If your entity model implements these interfaces, you can define a property as a model.
In your example however, you use an ObservableCollection (thus a list of models) as a model. That is not supported (or, again, the collection must support IEditableObject and INotifyPropertyChanged).
Here's the situation in its most simplified form using the EF5 Code-First approach:
public abstract class EntityBase<PK>
{
public PK ID { get; set; }
}
public class Country : EntityBase<string>
{
public string Name { get; set; }
}
public class Address : EntityBase<int>
{
[Required]
public string CountryID { get; set; }
public Country Country { get; set; }
// ... other address properties ...
}
The one-to-many relationship between Address and Country is set up with no cascade-delete like so:
modelBuilder.Entity<Address>()
.HasRequired(a => a.Country)
.WithMany()
.HasForeignKey(a => a.CountryID)
.WillCascadeOnDelete(false);
Finally, I have a generic base repository class with CRUD methods that call SaveChanges on the underlying DbContext to commit data changes atomically. E.g.:
public class EFRepository<T, PK> : IRepository<T, PK> where T : EntityBase<PK>
{
//
// ... other methods ...
//
public virtual void Delete(T instance)
{
// ... trigger validations, write to log, etc...
_dbContext.Set<T>().Remove(instance);
try
{
_dbContext.SaveChanges();
}
catch(Exception ex)
{
// ... handle the error ...
}
}
}
Part 1:
Scenario:
var countryRepo = new EFRepository<Country>();
var country = countryRepo.Save(new Country() { ID="??", Name="Test Country" });
var addressRepo = new EFRepository<Address>();
var address = addressRepo.Save(new Address() { Country=country });
countryRepo.Delete(country);
This should fail due to the existence of a dependent Address. However, afterwards the address ends up with a null in CountryID, which is invalid because Address.CountryID is required, so subsequent SaveChanges calls throw a validation exception unless the address is detached.
I expected that when an object is deleted, EF5 will be smart enough to first check for any cascade-delete constraints like the one above and, failing to find any, then proceed to delete the data. But exactly the opposite seems to be the case.
Is this a normal behaviour or am I doing something wrong?
Part 2:
Following a failed SaveChanges call, some Addresses are now in an invalid state in my DbContext and need to be restored to their original values. Of course, I can always do so explicitly for each entity type (Country, State, Order, etc.) by creating specialized repository classes and overriding Delete, but it smells big time. I'd much rather write some general purpose code to gracefully recover related entities after a failed SaveChanges call.
It would require interrogating DbContext to get all relationships in which an entity (e.g. Country) is the principal, regardless of whether or not its class defines navigational properties to dependent entities.
E.g. Country has no Addresses property, so I need to somehow find in DbContext the definition of the one-to-many relationship between Country and Address and use it to restore all related Addresses to their original values.
Is this possible?
Answering my own question in Part 2:
Here is my approach to checking for related dependents when deleting an entity on the principal end of a many-to-one relationship and where dependents are NOT exposed as a navigation collection in the principal (e.g. class Address has a Country property, but class Country doesn't have an Addresses collection).
DbContext
Add the following method to the context class:
/// <summary>
/// Returns an array of entities tracked by the
/// context that satisfy the filter criteria.
/// </summary>
public DbEntityEntry[] GetTrackedEntities<T>(
Expression<Func<DbEntityEntry<T>, bool>> filterCriteria)
where T : class
{
var result = new List<DbEntityEntry>();
var doesItMatch = filterCriteria.Compile();
foreach (var entry in this.ChangeTracker.Entries<T>())
{
if (doesItMatch(entry))
result.Add(entry);
}
return result.ToArray();
}
Repositories
Create a repository for each class that has some dependencies, override the Delete method and use the new GetTrackedEntities<T> method to get all related dependents and either:
explicitly delete them if they are cascade-deletable in code
detach them from the context if they are cascade-deletable in the DB itself
throw an exception if they are NOT cascade-deletable.
Example of the latter case:
public class EFCountryRepository :
EFReadWriteRepository<Country, string>,
ICountryRepository
{
public override void Delete(Country instance)
{
// Allow the Country to be deleted only if there are no dependent entities
// currently in the context that are NOT cascade-deletable.
if (
// are there any Regions in the context that belong to this Country?
_dbContext.GetTrackedEntities<Region>(e =>
e.Entity.CountryID == instance.ID ||
e.Entity.Country == instance).Length > 0
||
// are there any Addresses in the context that belong to this Country?
_dbContext.GetTrackedEntities<Address>(e =>
e.Entity.CountryID == instance.ID ||
e.Entity.Country == instance).Length > 0
)
throw new Exception(String.Format(
"Country '{0}' is in use and cannot be deleted.", instance.ID));
base.Delete(instance);
}
// ... other methods ...
}
Example of a case where cascade-deleting will be done by the DB itself, so all we need to do is detach the dependents from the context:
public class EFOrderRepository :
EFReadWriteRepository<Order, string>,
IOrderRepository
{
public override void Delete(Order instance)
{
foreach (var orderItem in _dbContext.GetTrackedEntities<OrderItem>(e =>
e.Entity.OrderID == instance.ID ||
e.Entity.Order == instance))
{
_dbContext.Entry(orderItem).State = System.Data.EntityState.Detached;
}
base.Delete(instance);
}
// ... other methods ...
}
Hope someone will find this solution helpful.
I have a status field on a class that has an ID and a Name. I'm not using an enum to model it, but rather a class with some static values, like this:
public class MailoutStatus : IEntity
{
public static MailoutStatus Draft = new MailoutStatus() { Id = 1, Name = "Draft" };
public static MailoutStatus Scheduled = new MailoutStatus() { Id = 2, Name = "Scheduled" };
public static MailoutStatus Cancelled = new MailoutStatus() { Id = 3, Name = "Cancelled" };
public static MailoutStatus Sent = new MailoutStatus() { Id = 4, Name = "Sent" };
public int Id { get; set; }
public string Name { get; set; }
...
}
Now I want to set this status value on the object it describes, like so:
var repo = new MailoutRepository();
var mailout = repo.Get(1);
mailout.Status = MailoutStatus.Cancelled;
repo.Update(mailout);
repo.CommitChanges();
However, this code will see MailoutStatus.Cancelled as a new entity and will insert a new row into the MailoutStatus table, ignoring the ID that is already on Cancelled and adding a new IDENTITY generated ID (for instance, 5). I can prevent this by adding an entityvalidation stuff, but that just makes the above blow up due to the validation failure.
I can work around the issue using this code:
var repo = new MailoutRepository();
var mailout = repo.Get(1);
mailout.Status = new MailoutStatusRepository().Get(MailoutStatus.Cancelled.Id);
repo.Update(mailout);
repo.CommitChanges();
This works because now Entity Framework knows about the MailoutStatus that I'm fetching and is tracking its state, etc. But it's really crappy to have to write that much code just to set a status. I also don't want to use an enum for other reasons and I don't want MailoutStatus to know anything about persistence. Any ideas?
Here's how I solved it.
I defined an attribute named NotTrackedAttribute and apply that on entities like Status. Then override the SaveChanges method of the derived context as follows. Reset the tracked changes to those entities
public override int SaveChanges()
{
var changedEntities = ChangeTracker.Entries();
foreach (var changedEntity in changedEntities)
{
var entity = changedEntity.Entity;
//ignore the types that are marked as NotTracked
if (Attribute.IsDefined(entity.GetType(), typeof(NotTrackedAttribute)))
{
changedEntity.State = EntityState.Unchanged;
continue;
}
}
return base.SaveChanges();
}
The attribute
/// <summary>
/// Indicates that a Type having this attribute should not be persisted.
/// </summary>
[AttributeUsage(AttributeTargets.Class, AllowMultiple = false, Inherited = true)]
public class NotTrackedAttribute : Attribute
{
}
Then use it as follows
[NotTracked]
public class MailoutStatus
{
}
You're already duplicating what's in the database. If you change your model to now just have an integer status, then you can change the MailoutStatus to a static int and it will just work.
In other words, what are you gaining by having MailoutStatus as another entity, when in fact it's just a lookup value?
Now EF is supporting enums. http://blogs.msdn.com/b/efdesign/archive/2011/06/29/enumeration-support-in-entity-framework.aspx. In code first you can have a discriminater column to map enum.
Or else this is a good solution Enums with EF code-first - standard method to seeding DB and then using?