Based on other posts such as Entity Framework and DbContext - Object Tracking
it would appear the simplified DBContext interface doesnt expose the to set No tracking on basic queries.
A little blog showing how with Object context
http://blogs.microsoft.co.il/blogs/gilf/archive/2009/02/20/disabling-change-tracking-in-entity-framework.aspx
What is a good approach to loading results via the DbContext as not tracked?
How are the performance conscious doing this if using Dbcontext ?
ie have base GetList method I would like to improve for performance reasons.
public DbSet<T> EntityDbSet { get { return _context.Set<T>(); } }
public virtual IQueryable<T> GetList(Expression<Func<T, bool>> predicate)
{
return EntityDbSet.Where(predicate);
}
The AsNoTracking is an extension on IQueryable.
You can update your function above with:
public virtual IQueryable<T> GetList(Expression<Func<T, bool>> predicate)
{
return EntityDbSet.Where(predicate).AsNoTracking();
}
Related
I am trying to implement a Generic repository as described in
https://codingblast.com/entity-framework-core-generic-repository/
It seems the generic DbSet does not have implemention for method AsNoTracking( ), am i not using the correct syntax? How to fix this issue
public class BaseRepository<TEntity> : IGenericRepository<TEntity>
where TEntity : class
{
private readonly DbContext _dbContext;
public BaseRepository(DbContext dbContext)
{
_dbContext = dbContext;
}
public IQueryable<TEntity> GetAll()
{
return _dbContext.Set<TEntity>().AsNoTracking();
}
}
There is nothing to fix here.
AsNoTracking method only configures query in a way that once it gets enumerated it won't track changes on those entities.
This is useful when you are doing read only and will not do any editing in that procedure. It is done for speed and efficiency.
So the method has no functionality that can be Async.
You will use Async methods when enumerating query, like:
ToListAsync() or
SingleOrDefaultAsync()
I have implemented Repository Pattern and Unit of Work into my ASP.NET Web API project.
It's working great. Now one question came to me about a Repository that can handle all about Setup Catalogs in my application.
Right now I have to create into my Unit of Work all public repositories that make a reference to an EF entity like below:
public IRepository<Document> Document { get { return GetStandardRepo<Document>(); } }
Where Document is an EF Entity. IRepository implements the following methods:
public interface IRepository<T> where T : class
{
IQueryable<T> GetAll();
IQueryable<T> GetAllReadOnly();
T GetById(int id);
void Add(T entity);
void Update(T entity);
void Delete(T entity);
void Delete(int id);
}
I have about 20 tables for Setup Catalogs in my database so If I follow this pattern I will have to create 20:
public IRepository<SetupEmployeeType> Document { get { return GetStandardRepo<SetupEmployeeType>(); } }
public IRepository<SetupMaritalStatus> Document { get { return GetStandardRepo<SetupMaritalStatus>(); } }
public IRepository<SetupRelationshipCode> Document { get { return GetStandardRepo<SetupRelationshipCode>(); } }
public IRepository<SetupLocationType> Document { get { return GetStandardRepo<SetupLocationType>(); } }
.....
.....
One solution I was thinking is to create my own custom IRepository implementation maybe ICatalogRepository like below:
public class CatalogRepository : EFRepository<EF Entity>, ICatalogRepository
{
public CatalogRepository (DbContext context) : base(context) { }
public IEnumerable<SetupEmployeeType> GetEmployeeTypes()
{
var catalog = DbContext
.Set<SetupEmployeeType>()
.ToList();
return catalog;
}
public IEnumerable<SetupMaritalStatus> GetMaritalStatus()
{
var catalog = DbContext
.Set<SetupMaritalStatus>()
.ToList();
return catalog;
}
}
My question is that CatalogRepository has to inherits from EFRepository but T is not just one entity because I will return diferent entities from diferent methods.
Is that the correct way to do this?
Yeah, don't use this anti pattern (generic repository wrapping DbContext while exposing EF entities). If you really want to use the Repository make the repository interface return ONLY business (or view models if it's a query repo) objects, never IQueryable or other details exposing EF or whatever are you using.
Simply put create a repository for your NEEDS, forget about generic stuff it's an anti pattern. So your CatalogRepository will use a DbContext to issue all the queries needed, then assemble a view model/business object from the results and returns that.
The app will know only about the Repo, never about EF. The queries will remain at the DAL level (not in your app/service/controller) and your app is decoupled, Separation of Concerns is respected.
A class wrapping DbContext is at best useless (what value does it bring?) and at worst a leaky abstraction. Make your life easier, if you want to work directly with EF entities and EF, work directly with EF. If you want to decouple the rest of the app from persistence details (note I've said persistence, not rdbms) use Repository properly. But don't kid yourself you're using the Repository pattern just because you have a class named repository. You should know exactly why are you using a pattern and what benefits it brings to your situation. It's not best practice if you don't understand why.
I am ASP.NET MVC newbie (but .NET experienced dev) and I am trying to learn how to properly set web application infrastructure.
Repository pattern is what I am copping these days and after reading dozens of blogs/articles/answers in the past few days I am still not sure how to use it the right way. I am learning from the Pro ASP.NET MVC 4 Adam Freeman and here is the code for repository interface based on this book:
public interface IRepository<T>
{
IQueryable<T> FindAll();
IQueryable<T> Find(Expression<Func<T, bool>> predicate);
void Add(T newEntity);
void Remove(T entity);
T FindById(long id);
}
After more research online I realized that many people think that returning IQueryable from repository is bad practice and I can (mostly) understand why. However, I can't seem to find answer on what exactly is the alternative? I know about idea of having a custom repository, for each entity, that has specialized method for each possible query which would basically return IEnumerable and not IQueryable... but this just doesn't seem right to me (it's not elegant solution, too many code writing and possible code redundancy etc...).
What are other alternatives?
You have two alternatives.
Specification pattern
The first one is to use the specification pattern. You create a set of classes which are used to limit the search result.
The wikipedia article is a bit poor since it doesn't show how to write business specifications (i.e. "real" specifications). But you basically use the lower level specs (And/Or etc) inside your business specs.
By doing so you can have simpler repository classes and instead code those specifications.
Specific repositories.
Create a repository for every root aggregate (Order, User etc). Each repository have unique query methods that apply to the specific business requirements.
The user repository could have for instance
IPagedResult<User> FindDisabledUser(int pageNumber, int pageSize);
And the order repository could have
IPagedResult<User> GetOrdersReadyForShipping(DateTime orderAfterThisDate);
I've written a set of data layer articles: http://blog.gauffin.org/tag/data-access/. One of those also explains why it's not a good idea to expose IQueryable<T> in your repositories.
As per my comment underneath the original question, this is how I would implement a repository needing more complex query requirements. I have also included my DbContext object for the Entity Framework.
I like this pattern because it hides the Entity Framework implementation behind the repository ensuring that the Entity Framework is not tightly coupled with your application.
public class PersonRepository: IPersonRepository
{
public List<Person> ReadAll()
{
using (var context = new EfContext())
return context.Persons.ToList();
}
public List<Person> ReadPage(int pageIndex, int itemCount)
{
using (var context = new EfContext())
return context.Persons
.Skip(pageIndex * itemCount)
.Take(itemCount)
.ToList();
}
public List<Person> ReadAllWhoseNamesStartWith(string nameExpression)
{
using (var context = new EfContext())
return context.Persons
.Where(r => r.Name.StartsWith(nameExpression)
.ToList();
}
public List<Person> ReadAllWhoseFavouriteColorIs(string color)
{
using (var context = new EfContext())
return context.Persons
.Where(r => r.FavoriteColor.StartsWith(color)
.ToList();
}
}
public class EfContext: DbContext
{
public EfContext(): base("DefaultConnection")
{
}
public DbSet<Person> Persons { get; set; }
public DbSet<Car> Cars { get; set; }
public DbSet<Car> Houses { get; set; }
protected override void OnModelCreating(DbModelBuilder modelBuilder)
{
Database.SetInitializer<EfContext>(null);
base.OnModelCreating(modelBuilder);
}
}
Why there is no IDbContext interface in the Entity Framework? Wouldn't it be easier to test things if there was an existing interface with methods like SaveChanges() etc. from which you could derive your custom database context interface?
public interface ICustomDbContext : IDbContext
{
// add entity set properties to existing set of methods in IDbContext
IDbSet<SomeEntity> SomeEntities { get; }
}
I see this IDbContext:
See this link And then you make a new partial class for your Entities Context With That interface.
public partial class YourModelEntities : DbContext, IDbContext
EDITED:
I edited this post, This Works for me.
My Context
namespace dao
{
public interface ContextI : IDisposable
{
DbSet<TEntity> Set<TEntity>() where TEntity : class;
DbSet Set(Type entityType);
int SaveChanges();
IEnumerable<DbEntityValidationResult> GetValidationErrors();
DbEntityEntry<TEntity> Entry<TEntity>(TEntity entity) where TEntity:class;
DbEntityEntry Entry(object entity);
string ConnectionString { get; set; }
bool AutoDetectChangedEnabled { get; set; }
void ExecuteSqlCommand(string p, params object[] o);
void ExecuteSqlCommand(string p);
}
}
YourModelEntities is your auto-generated partial class, and your need to create a new partial class with the same name, then add your new context interface, for this example is ContextI
NOTE: The interface hasn't implement all methods, because the methods are implemented in your auto-generate code.
namespace dao
{
public partial class YourModelEntities :DbContext, ContextI
{
public string ConnectionString
{
get
{
return this.Database.Connection.ConnectionString;
}
set
{
this.Database.Connection.ConnectionString = value;
}
}
bool AutoDetectChangedEnabled
{
get
{
return true;
}
set
{
throw new NotImplementedException();
}
}
public void ExecuteSqlCommand(string p,params object[] os)
{
this.Database.ExecuteSqlCommand(p, os);
}
public void ExecuteSqlCommand(string p)
{
this.Database.ExecuteSqlCommand(p);
}
bool ContextI.AutoDetectChangedEnabled
{
get
{
return this.Configuration.AutoDetectChangesEnabled;
}
set
{
this.Configuration.AutoDetectChangesEnabled = value;
}
}
}
}
I was thinking also about that, I assume you are going to use it for mocking DbContext. I find no reason for that, except that you will need to implement your own DbSet manually in your anyway for your mocked class (so will need to rewrite your own interface anyway).
Just create a mock DbContext extending your production DbContext overriding the methods that complicate testing. That way, any changes to the production DbContext are automatically reflected in the tests, save for the overridden methods. For any other classes that deal with persistence and take the DbContext just extend them as well passing in the extended mock DbContext.
namespace Test.Mocks
{
public sealed class MockDatabaseContext : MainProject.Persistence.Database.DatabaseContext
{
public MockDatabaseContext(ConfigurationWrapper config) : base(config)
{
}
protected override void OnConfiguring(DbContextOptionsBuilder optionsBuilder)
{
var dbPath = "test.db";
optionsBuilder.UseSqlite($"Filename={dbPath}");
}
}
}
namespace Test.Mocks
{
public class MockInventoryFacade : InventoryFacade
{
public MockInventoryFacade(MockDatabaseContext databaseContext) : base(databaseContext)
{
}
}
}
There is no IDbContext because it would be useless, the only implementation of it would be the DbContext.
EF team is also going this way with IDbSet if you look at this design meeting note
For me, the real problem with EF when it comes to unit testing is the DbConnection in the DbContext, fortunately there is Effort a nice project on codeplex that starts to fill this.
Effort is a powerful tool that enables a convenient way to create automated tests for Entity Framework based applications.
It is basically an ADO.NET provider that executes all the data operations on a lightweight in-process main memory database instead of a traditional external database. It provides some intuitive helper methods too that make really easy to use this provider with existing ObjectContext or DbContext classes. A simple addition to existing code might be enough to create data driven tests that can run without the presence of the external database.
With this, you can leave your DbContext and DbSet as is and do your unit tests easily.
The only drawback with this is the difference between Linq providers where some unit tests may pass with effort and not with the real backend.
UPDATE with EF7
I still maintain that IDbContext would be useless and the problem comes from the DbConnection.
EF7 will not have an IDbContext either, in order to do unit testing they are now giving an in memory provider.
You can see Rowan Miller doing a demo here: Modern Data Applications with Entity Framework 7
I would like to create a base class that is somewhat generic for all of my entities. The class would have methods like Save(), Delete(), GetByID() and some other basic functionality and properties. I have more experience with Linq to SQL and was hoping to get some good examples for something similar in the EF. Thank you.
Like this:
public abstract class BaseObject<T>
{
public void Delete(T entity)
{
db.DeleteObject(entity);
db.SaveChanges();
}
public void Update(T entity)
{
db.AcceptAllChanges();
db.SaveChanges();
}
}
public interface IBaseRepository<T>
{
void Add(T entity);
T GetById(int id);
IQueryable<T> GetAll();
}
The ADO.NET Entity Framework supports both Table-per-hierarchy and Table-per-type inheritance. I suggest you start here to see how it works.