I want to define a base configuration (for some reason) for all model configuration(which using fluent api on them), so i create BaseConfigration class:
public class BaseConfigration<T> : EntityTypeBuilder<T> where T : class
{
public BaseConfigration(InternalEntityTypeBuilder builder) :base(builder)
{
}
}
and all of other configuration inherit from it:
public class LoyaltyActivityConfig : BaseConfigration<LoyaltyActivity>
{
public LoyaltyActivityConfig(InternalEntityTypeBuilder builder) : base(builder)
{
this.Property(x => x.Title).HasMaxLength(100);
}
}
in this point all thing goes right, but when i want to introduce this configuration in OnModelCreating method:
new LoyaltyActivityConfig(modelBuilder.Entity<NotificationPlatform>());
it gives me error:
cannot convert from 'Microsoft.EntityFrameworkCore.Metadata.Builders.EntityTypeBuilder' to 'Microsoft.EntityFrameworkCore.Metadata.Internal.InternalEntityTypeBuilder'
How can i do it?
As the exception message says, you are using incorrect type. During OnModelCreating you have EntityTypeBuilder<T> object. InternalEntityTypeBuilder should not be used in user code as its internal to EF core as said in documentation.
To define a BaseConfiguration which will be applied to each entity type in the model and derived by EntityTypeConfiguration, code should be organized in following manner:
public class BaseConfiguration<T> where T : class
{
public BaseConfiguration(EntityTypeBuilder<T> entityTypeBuilder)
{
// Write fluent API code here which will be applied to all entityTypes in the model
entityTypeBuilder.HasKey("Id");
}
}
public class LoyaltyActivityConfig : BaseConfiguration<LoyaltyActivity>
{
public LoyaltyActivityConfig(EntityTypeBuilder<LoyaltyActivity> entityTypeBuilder)
: base(entityTypeBuilder)
{
// Write fluent API code here which will be applied to EntityType LoyaltyActivity only
entityTypeBuilder.Property(x => x.Title).HasMaxLength(100);
}
}
Then call above code from OnModelCreating like this
new LoyaltyActivityConfig(modelBuilder.Entity<LoyaltyActivity>());
Above method will call BaseConfiguration constructor followed by EntityTypeConfiguration constructor, applying all fluent API code.
Few things to remember here,
In BaseConfiguration even if you have generic EntityTypeBuilder you will not be able to use generic methods since T is unknown type. You can define an interface which will be implemented by every T (all entity types in the model) and use generic methods afterwards. Using non-generic methods will also get you same result though. Its just matter of readability.
You can also use method calls instead of constructor in Config classes to achieve the same.
To organize code like above, IEntityTypeConfiguration<TEntity> feature from EF6 has been implemented in EF core and will be available in 2.0 release. More info https://github.com/aspnet/EntityFramework/issues/2805
Related
How can I apply the :base("name=connectionstring_name") in ASP.NET Core?
Because my Visual Studio shows cannot convert from 'string' to 'Microsoft.EntityFrameworkCore.DbContextOptions' .
namespace SchoolDataLayer
{
public class Context: DbContext
{
public SchoolDBContext() : base("name=SchoolDBConnectionString")
{
}
}
}
public SchoolDBContext() : base("name=SchoolDBConnectionString")
As error says you should pass DbContextOptions class instead of connection string.
The DbContextOptions instance carries configuration information such as:
The database provider to use, typically selected by invoking a method such as UseSqlServer or UseSqlite. These extension methods require the corresponding provider package, such as Microsoft.EntityFrameworkCore.SqlServer or Microsoft.EntityFrameworkCore.Sqlite. The methods are defined in the Microsoft.EntityFrameworkCore namespace.
Any necessary connection string or identifier of the database instance, typically passed as an argument to the provider selection method mentioned above
Any provider-level optional behavior selectors, typically also chained inside the call to the provider selection method
Any general EF Core behavior selectors, typically chained after or before the provider selector method
here is an example:
public class Context: SchoolDbContext
{
public SchoolDbContext(DbContextOptions<SchoolDbContext> options)
: base(options)
{
}
}
for more information read https://learn.microsoft.com/en-us/ef/core/miscellaneous/configuring-dbcontext
I'm trying to implement a repository solution for Entity Framework but I am having trouble registering the types that include generics using Unity.
Given:
// IRepository interface
public interface IRepository<TEntity>
{
// omitted for brevity
}
// Repository implementation
public class Repository<TEntity, TContext> : IRepository<TEntity>, IDisposable
where TEntity : class
where TContext : DbContext
{
// omitted for brevity
}
// service layer constructor
public MyServiceConstructor(IRepository<Account> repository)
{
_repository = repository;
}
I need to register the type mapping for IRepository to Repository. but I'm having trouble with the Unity syntax for this kind of mapping.
I have tried the following with no luck:
container.RegisterType<IRepository<>, typeof(Repository<,>)>();
container.RegisterType<typeof(IRepository<>), Repository<,>>();
EDIT
Based, on #Steven response I have the following implementation now:
// UnityRepository implementation
public class UnityRepository<TEntity> : Repository<TEntity, MyDbContextEntities>
where TEntity : class
{
public UnityRepository() : base(new MyDbContextEntities()) { }
}
// Unity bootstrapper
container.RegisterType(typeof(IRepository<>), typeof(UnityRepository<>));
You are trying to do the following:
container.RegisterType(typeof(IRepository<>), typeof(Repository<,>));
This would normally work, but won't do the trick in this case, since there is IRepository<TEntity> has one generic argument and Repository<TEntity, TContext> has two, and Unity (obviously) can't guess what type it should fill in for TContext.
What you need is this:
container.RegisterType(
typeof(IRepository<>),
typeof(Repository<, MyDbContextEntities>));
In other words, you'd want to supply the Repository<TEntity, TContext> as a partial open generic type (with one parameter filled in). Unfortunately, the C# compiler does not support this.
But even if the C# did support this, Unity doesn't support partial open generic types. In fact most IoC libraries eworks don't support this. And for that one library that does support it, you would still have to do the following (nasty thing) to create the partial open generic type:
Type myDbContextEntitiesRepositoryType =
typeof(Repository<,>).MakeGenericType(
typeof(Repository<,>).GetGenericParameters().First(),
typeof(MyDbContextEntities));
There's a easy trick work around to get this to work though: define a derived class with one generic type:
// Special implementation inside your Composition Root
public class UnityRepository<TEntity> : Repository<TEntity, MyDbContextEntities>
where TEntity : class
{
public UnityRepository([dependencies]) : base([dependencies]) { }
}
Now we can easily register this open generic type:
container.RegisterType(typeof(IRepository<>), typeof(UnityRepository<>));
Is it possible to add summary properties(no database column) according LINQ from another property(column) in EF generated class from database and this property don't update(delete or remove from class) when update model from database(because this property(cloumn) is not on database)
Yes, it is. Classed generated by Entity Framework as an Entitied are always marked partial. It lets you extend the functionality with your own properties or method.
Let say your entity class is named Post. You can extend it with code like that:
public partial class Post
{
public int Average
{
get
{
return this.Items.Average();
}
}
}
Because it's not a part of designer-generated file it won't be overwritten when it's regenerated. However, there is one requirement to make it work: your custom part of Post class has to be in exactly the same namespace as code generated by EF.
Try using the [NotMapped] attribute on a property in a partial class. This will be ignored by Entity Framework.
public partial class EntityName
{
[NotMapped]
public int CalculatedProperty
{
get
{
return Numbers.Sum();
}
}
}
The default constructor in a generated Entity Framework Entities file is like this:
public ProjectEntities() : base("name=ProjectEntities", "ProjectEntities")
{
this.OnContextCreated();
}
I want to change it to:
public ProjectEntities() : base(UtilClass.GetEnvDependantConnectionStringName(), "ProjectEntities")
{
this.OnContextCreated();
}
This is because I want to have a different connection string for all the dev environments and the production environment, and have no chance they are mixed up (which is what my custom method checks).
How do I do that? This code is thrown away every time the designer file is regenerated.
You need to create another file alongside the auto-created ProjectEntities.Designer.cs, say ProjectEntities.cs. In that you use partial to extend the functionality of your entities class like this:
public partial class ProjectEntities : ObjectContext
{
partial void OnContextCreated()
{
this.Connection.ConnectionString = UtilClass.GetEnvDependantConnectionString();
}
}
The file won't then get changed when you regenerate the .Designer.cs file. You'll have to fetch the connection string yourself...
We fixed it by calling our entities ProjectEntitiesPrivate, and what was partial class ProjectEntities before, is now a non partial class ProjectEntities : ProjectEntitiesPrivate, with the constructor I need:
public class ProjectEntities: ProjectEntitiesPrivate
{
public ProjectEntities():base(UtilClass.GetEnvDependantConnectionStringName())
{
}
....
For a simple repository
public interface ISimpleRepository<T>
{
IApplicationState AppState { get; set; }
void Add(T instance);
void Delete(T instance);
void Delete(Guid rowGuid);
IQueryable<T> GetAll();
T Load(Guid rowGuid);
void SaveChanges();
void Update(T instance);
}
my implementation of the Load() method for specific repository for class Product might look like this:
public Product Load(Guid rowid)
{
return (from c in _ctx.Products where c.id == rowid select c).FirstOrDefault();
}
Now this is assumed when my repository implementation class looks like this:
public class EntityFrameworkProductsProvider : IRepository<Product> ...
What if I had like dozens or hundreds of this small and simple entities that would all use the same behaviour when doing CRUDs (use the same implementation of methods)? I certainly don't want to go and create a class to implement IRepository for each one of them..
I want something like this:
public class EntityFrameworkDefaultProvider<T> : IRepository<T> ...
but I don't know how to implement the LINQ Select expression then because of course I can't write from e in _ctx.T where e... or do I?
I haven't run into this scenario yet because so far I only had very specific entities with custom repository implementation.
Because you tagged your question with entity-framework and entity-framework-4 I assume you are using ObjectContext API. ObjectContext offers method CreateObjectSet<T> which is equivalent of Set<T> on DbContext.
This question is actually duplicate of either:
Generic GetById with DbContext
Generic GetById with ObjectContext
Instead of writing _ctx.Products, you can write _ctx.Set<T>. That takes care of half of the problem (you need to add a generic constraint where T: class to your repository)
Then, if rowid is the object's key, you can use _ctx.Set<T>.Find(rowid) instead of a LINQ query to retrieve by Id.
Alternatively, you can create a base interface IHaveId (or a BaseEntity class, whatever you like) which has the Id property, and then add that as an generic constraint on T, so you can use it in your queries.
If you're using EF 4.1, see the sample generic repository here:
http://www.asp.net/entity-framework/tutorials/implementing-the-repository-and-unit-of-work-patterns-in-an-asp-net-mvc-application
I know that this is possible in EF4.1 with the DbContext API, where you have a "Set" method on the context that gets you the entity set corresponding to the type T. this way, you could have your repository like this:
public class EntityFrameworkDefaultProvider<T> : IRepository<T> where T:class
{
public T Load(Guid rowId)
{
return _context.Set<T>().Find(rowId);
}
}
one more remark: I think you could use this syntax :
return _ctx.Products.FirstOrDefault(c=>c.id == rowid);
to get the entity you want instead of using the (from... in...). it's clearer (in my opinion) :)
Hope this helps