What Can/Cannot be done inside a Generic repository - asp.net-mvc

I am working on an asp.net mvc-5 with Entity framework 6. now currently i am not using any kind on generic repositories , as the ones mentioned here:-
Link-1
&
Link-2
now the generic repository gives you a feeling that you can do everything in a generic way.. but inside these 2 links seems what can be generilzed are the basic operations for get, add, delete & modify which are by defualt provided inside Entity framework. so can anyone adivce on thses question regading using Generic repositories with EF-6 & MVC-5:-
1.is it really a good approach of using Generic repo ? as seems generic repo will just provide what EF already provide !!
2.let say i have two Parent/Child (DataCenter/Zone) objects:-
public class DataCenter
{
public int ID { get; set; }
public string Name { get; set; }
public byte[] timestamp { get; set; }
public virtual ICollection<Zone> Zones { get; set; }
}
public class Zone
{
public int ZoneID { get; set; }
public string Name { get; set; }
public int DataCenterID { get; set; }
public virtual DataCenter DataCenter { get; set; }
}
now using the Generic repository i can Get,Add,Edit,Delete these 2 objects using the same generic repo methods. but let say i want to retrieve all the Zones related to a specific Datacenter as follow:-
var results = entity.DataCenters.SingleOrDefault(a => a.ID == id).Zones.Where(a => a.Name.Contains("1"));
so can the generic repository support such a query , in a way that i can re-use the query with another object types (other than Datacenter & zones). for example to have a generic query :- to get a parent object by ID and for its child to get the childs that have their names contain the word "1" ?? and what if the parent have multiple child types !! will the generic repository support non-generic queries and operations ?

I went through the same question... I first did a specific repository, then I changed to a generic. But I've ended up having to code so much specific queries, that I decide to change for non-generic repositories, returning ToList (I didn't want IQueryable) and using Unit of Work pattern. Now I think I'm happy with the way things are.
Edit:
Query the child by it's property, bringing back the parent too (is that what you want?):
return await _context.Entity.Include(e => e.Parent)
.Where(e => e.SomeProp == someParam)
.ToListAsync();
Or, Querychild, using some property in the parent, bringing back The parent:
return await _context.Entity.Include(e => e.Parent)
.Where(e => e.Parent.SomeProp == someParam)
.ToListAsync();

Related

How to include related entities when getting ApplicationUser from DB? [duplicate]

I've extended IdentityUser to include a navigation property for the user's address, however when getting the user with UserManager.FindByEmailAsync, the navigation property isn't populated. Does ASP.NET Identity Core have some way to populate navigation properties like Entity Framework's Include(), or do I have to do it manually?
I've set up the navigation property like this:
public class MyUser : IdentityUser
{
public int? AddressId { get; set; }
[ForeignKey(nameof(AddressId))]
public virtual Address Address { get; set; }
}
public class Address
{
[Key]
public int Id { get; set; }
public string Street { get; set; }
public string Town { get; set; }
public string Country { get; set; }
}
Unfortunately, you have to either do it manually or create your own IUserStore<IdentityUser> where you load related data in the FindByEmailAsync method:
public class MyStore : IUserStore<IdentityUser>, // the rest of the interfaces
{
// ... implement the dozens of methods
public async Task<IdentityUser> FindByEmailAsync(string normalizedEmail, CancellationToken token)
{
return await context.Users
.Include(x => x.Address)
.SingleAsync(x => x.Email == normalizedEmail);
}
}
Of course, implementing the entire store just for this isn't the best option.
You can also query the store directly, though:
UserManager<IdentityUser> userManager; // DI injected
var user = await userManager.Users
.Include(x => x.Address)
.SingleAsync(x => x.NormalizedEmail == email);
The short answer: you can't. However, there's options:
Explicitly load the relation later:
await context.Entry(user).Reference(x => x.Address).LoadAsync();
This will require issuing an additional query of course, but you can continue to pull the user via UserManager.
Just use the context. You don't have to use UserManager. It just makes some things a little simpler. You can always fallback to querying directly via the context:
var user = context.Users.Include(x => x.Address).SingleOrDefaultAsync(x=> x.Id == User.Identity.GetUserId());
FWIW, you don't need virtual on your navigation property. That's for lazy-loading, which EF Core currently does not support. (Though, EF Core 2.1, currently in preview, will actually support lazy-loading.) Regardless, lazy-loading is a bad idea more often than not, so you should still stick to either eagerly or explicitly loading your relationships.
Update for .NET 6.0 with EF Core 6.0:
You can now configure the property to be automatically included on every query.
modelBuilder.Entity<MyUser>().Navigation(e => e.Address).AutoInclude();
For more info check out:
https://learn.microsoft.com/en-us/ef/core/querying/related-data/eager#model-configuration-for-auto-including-navigations
I found it useful to write an extension on the UserManager class.
public static async Task<MyUser> FindByUserAsync(
this UserManager<MyUser> input,
ClaimsPrincipal user )
{
return await input.Users
.Include(x => x.InverseNavigationTable)
.SingleOrDefaultAsync(x => x.NormalizedUserName == user.Identity.Name.ToUpper());
}
Best Option in my case is to add a package reference to Microsoft.EntityFrameworkCore.Proxies and then in your services use the UseLazyLoadingProxies
.AddDbContext<YourDbContext>(
b => b.UseLazyLoadingProxies()
.UseSqlServer(myConnectionString));
More infos
https://learn.microsoft.com/de-de/ef/core/querying/related-data/lazy

Setting up for selective auditing in same DbContext

I just stumbled onto Audit.Net and I'm hooked. I went through the Audit.Net Entity Framework (6) documentation and am a bit lost in the output part.
My solution is a bit many-layers design:
Mvc 5 website
Wcf Client
Using WcfClientProxyGenerator
Wcf Service
Separate IService Contracts Library
All interfaces expose BDOs
Business Logic
Seperate BDO Library
Data Access
Reference EF6
Reference Audit.Net
DTOs
Entity Framwework Library
Has EDMX only
Reference Audit.Net
Reference: My EDMX is named Focus
Usage
I manage to modify the FocusModel.Context.tt from:
partial class <#=code.Escape(container)#> : DbContext
To:
partial class <#=code.Escape(container)#> : Audit.EntityFramework.AuditDbContext
Configuration
I found the default setting for Mode, IncludeEntityObjects, & AuditEventType were to my liking. the attribute for Include/Ignore entities/properties were straightforward as well.
Output
This is where I'm confused. I need to audit to the same database preferably to Audit tables for selected entities. Every entity in my database has composite PKs. How do I set the output mode in this scenario? Also, in my solution setup, the starting point for all projects that are behind the WCF Service is the WCF service itself. Does this mean that the point to Fluent-API-configure Audit.Net is here?
Have you seen the main Audit.NET documentation, specifically the output data providers?
I need to audit to the same database preferably to Audit tables for selected entities. Every entity in my database has composite PKs.
So you can use the EF data provider. It works with any kind of primary key.
How do I set the output mode in this scenario?
I'm not sure what do you mean by output mode, but I'm guessing you ask about OptIn/OptOut to ignore your audit entities to be audited. If that's the case you have multiple options, like using AuditIgnore attribute on your audit POCO classes, or via the fluent-api OptIn()/OptOut() methods. See example below.
The starting point for all projects that are behind the WCF Service is the WCF service itself. Does this mean that the point to Fluent-API-configure Audit.Net is here?
You can configure the Audit.NET library in any place, but you must do it before any audit event creation, so it is recommended to be on your startup code, as soon as your app or service starts.
Sample code
The following is a minimal example showing how you can configure the Audit.NET and Audit.EntityFramework libraries.
Suppose you have the following schema:
public class Student
{
public int PK_1 { get; set; }
public string PK_2 { get; set; }
public string Name { get; set; }
}
public class Student_Audit
{
public int PK_1 { get; set; }
public string PK_2 { get; set; }
public string Name { get; set; }
public DateTime AuditDate { get; set; }
public string AuditAction { get; set; }
}
public class SchoolContext : AuditDbContext
{
protected override void OnModelCreating(ModelBuilder modelBuilder) //<--Tip: its not DbModelBuilder, its Microsoft.EntityFrameworkCore.ModelBuilder
{
modelBuilder.Entity<Student>().HasKey(c => new { c.PK_1, c.PK_2 });
modelBuilder.Entity<Student_Audit>().HasKey(c => new { c.PK_1, c.PK_2, c.AuditDate });
}
public DbSet<Student> Students { get; set; }
public DbSet<Student_Audit> Students_Audit { get; set; }
}
You can configure the library on your startup code as follows:
// Setup audit to use the EF data provider
Audit.Core.Configuration.Setup()
.UseEntityFramework(_ => _
.AuditTypeExplicitMapper(m => m
// Map Student to Student_Audit
.Map<Student, Student_Audit>((ev, ent, studentAudit) =>
{
//add the action name and the date to the audit entity
studentAudit.AuditAction = ent.Action;
studentAudit.AuditDate = DateTime.UtcNow;
})));
// Configure the EF audit behavior
Audit.EntityFramework.Configuration.Setup()
.ForContext<SchoolContext>(_ => _.IncludeEntityObjects())
.UseOptOut()
.Ignore<Student_Audit>(); // Do not audit the audit tables
And a test case:
using (var db = new SchoolContext())
{
db.Database.EnsureCreated();
var st = new Student() { PK_1 = 1, PK_2 = "one", Name = "John" };
db.Students.Add(st);
db.SaveChanges();
}
Will generate the following:

Multiple database contexts when using repository pattern

I am a bit lost right now... I've never seen this much divergent information regarding solution to the problem. But let us start from the beginning.
I am using ASP.NET MVC with Repositories injected to Controllers, thanks to the Ninject. I have 2 simple Entities: Admin with a list of created blog entries and Entries with one virtual Admin field.
Admin:
public class Admin
{
[Key, ScaffoldColumn(false)]
public int Id { get; set; }
[Required(ErrorMessage = "Zły login.")]
[StringLength(20), MinLength(3)]
[RegularExpression(#"^[a-zA-Z0-9]*$", ErrorMessage = "Special characters are not allowed.")]
public string Login { get; set; }
[Required(ErrorMessage = "Złe hasło.")]
[StringLength(20, MinimumLength = 3)]
[DataType(DataType.Password)]
[Display(Name = "Hasło")]
public string Password { get; set; }
public virtual List<Entry> CreatedEntries { get; set; } // napisane aktualności przez danego admina
}
Entry:
public class Entry
{
[Key, ScaffoldColumn(false)]
public int Id { get; set; }
[StringLength(200, MinimumLength = 2)]
[DataType(DataType.Text)]
[Display(Name = "Tytuł")]
public string Title { get; set; }
[Required, StringLength(2000), MinLength(3)]
[Display(Name = "Treść")]
[UIHint("tinymce_jquery_full"), AllowHtml]
public string Text { get; set; }
public virtual Admin Admin { get; set; }
}
You probably know where it is going, since this problem is... "classic" on stackoverflow.
In the Controller I want to bind one object to another:
entry.Admin = repAdmins.GetAdmin(User.Identity.Name);
repEntries.AddEntry(entry);
In the repository:
public void AddEntry(Entry entry)
{
db.Entries.Add(entry);
db.SaveChanges();
}
Of course I can't do that, because of famous "An entity object cannot be referenced by multiple instances of IEntityChangeTracker", which is a result of having separate database contexts in each repository.
When I was searching for a solution I already knew that probably the best way to solve it is to use one common context. And then I discovered Unit Of Work pattern. But here's when the real problems starts.
On many sites the solution to this is a bit different.
The repositories must have common generic interface (which I don't want to use, because I don't need to have each CRUD operation on each Entity, plus sometimes I need to have extra methods like "IfExists", etc.)
On few sites I've read that this whole abstraction is not needed, since abstraction is already provided with Entity Framework and UoW is implemented in DbContext (whatever that means)
The Unit Of Work pattern (at least from examples on the internet) seems to be a real pain for me...
I need some guidance... I learn ASP.NET MVC for only a year. For me it seems like it's a "triumph of form over content". Because... What I simply need is to bind one object to another. I'm starting to think that it was better when I simply had a context object in the Controller and I didn't need to build Eiffel Tower to achieve what's mentioned above :\ However I like idea of repositories...
I'll open by simply answering the question straight-out. Simply, your repository should take the context as a dependency (it should have a constructor that accepts a param of type DbContext). Your context should be managed by Ninject, and then injected into your repository and/or your controller. That way, everything always uses the same context. You should do all this in "request" scope, so that the context is specific to the current request.
That said, I'd like to hit some of your other points. First, a repository is just a method of access. It really shouldn't be dependent on the entity. It's okay to have methods that you don't intend to use on a particular entity: just don't use them. However, if you do want to enforce this, you can always use generic constraints and interfaces. For example, let's say you don't want update available on a particular entity. You could have interfaces like:
public interface ICreateable
{
}
public interface IUpdateable : ICreateable
{
}
Then, your entity that should not be updated will implement only ICreateable while other entities (which allow update) would implement IUpdateable (which by interface inheritance, also implement ICreateable). Finally, you would add constraints on your repository methods:
public void Create<TEntity>(TEntity entity)
where TEntity : class, ICreateable
public void Update<TEntity>(TEntity entity>)
where TEntity : class, IUpdateable
Since, the entity in question only implements ICreatable, it will not be eligible to be used as a type param to Update, so there's then no way to utilize that method.
Next, the advice to not use the repository/UoW patterns with Entity Framework is indeed because Entity Framework already implements these patterns. The repository pattern exists as a way to contain all the database querying logic (constructing SQL statements and such) in one place. That is the "abstraction" we're talking about here. In other words, instead of directly constructing SQL statements in your application code, that code is abstracted away into a repository. However, this is exactly what Entity Framework does, which is why you don't need to do it again. The Unit of Work pattern exists as a method to orchestrate the work of multiple repositories, allowing things like transactions. However, again, Entity Framework does all this.
The only reason to add any further abstraction is if you want to abstract the actual provider, i.e. Entity Framework itself. For example, you could have an interface like IRepository and then create implementations like EntityFrameworkRepository, NHibernateRepository, WebApiRepository, etc. Your application would only ever depend on IRepository, and you could then sub in different implementations as needed. If you're not going to do this, or you will always be using Entity Framework, then you might as well just use your context directly. Any further abstraction is just something else to maintain with no benefit at all to your application.
Finally, yes, the Unit of Work pattern is a real pain to everyone, not just you. Which is why I forgo it entirely. I use what I call a "truly generic repository", which utilizes generic methods and interfaces to handle any entity I want to throw at it. That means it acts not only as a repository but also a unit of work as well. You only need one instance per context and it's provider-agnostic. For more information check out the article I wrote on the subject over on my website.
The following example shows how to use the same context within multiple repositories. To simplify it, I did not use interfaces and nor did I use a container to inject dependencies.
Controller class:
public class HomeController : Controller
{
Context context;
AdminRepository adminRepository;
EntryRepository entryRepository;
public HomeController()
{
context = new Context();
adminRepository = new AdminRepository(context);
entryRepository = new EntryRepository(context);
}
// GET: Home
public ActionResult Index()
{
string login = "MyLogin";
Admin admin = adminRepository.GetAdmin(login);
Entry entry = new Entry() { Admin = admin};
entryRepository.AddEntry(entry);
return View(entry);
}
}
Repositories:
public class AdminRepository
{
Context context;
public AdminRepository(Context context)
{
this.context = context;
// This seeds the database
Admin admin = new Admin() { Login = "MyLogin" };
this.context.Admins.Add(admin);
this.context.SaveChanges();
}
public Admin GetAdmin(string login)
{
return context.Admins.Where(a => a.Login == login).FirstOrDefault();
}
}
public class EntryRepository
{
Context context;
public EntryRepository(Context context)
{
this.context = context;
}
public void AddEntry(Entry entry){
context.Entrys.Add(entry);
context.SaveChanges();
}
}
Context class:
public class Context : DbContext
{
public Context()
{
Database.SetInitializer<Context>(new DropCreateDatabaseAlways<Context>());
Database.Initialize(true);
}
public DbSet<Admin> Admins { get; set; }
public DbSet<Entry> Entrys { get; set; }
}
Modified Models:
public class Admin
{
public int Id { get; set; }
public string Login { get; set; }
}
public class Entry
{
public int Id { get; set; }
public virtual Admin Admin { get; set; }
}

Unable to Add Controller (with scaffolding) ASP.NET MVC

This has been addressed in multiple other questions, but alas, I have tried all the solutions posted there with no success. I'm developing an ASP.NET MVC application, using Code-First EF. I am trying to take advantage of the scaffolding built in so that it can automatically create a Controller for me based off my Model and DbContext. However, I am getting the following error when I try to create a Controller in this way:
'Unable to retrieve metadata for Employer.' Using the same DbCompiledModel to create contexts against different types of database servers is not supported. Instead, create a separate DbCompiledModel for each type of server being used.
The code for my model, Employer, my DbContext, MyDataContext, and my web.config file follow:
//Employer.cs
public class Employer : Organization, IEmployer
{
public virtual PhysicalAddress Address { get; set; }
public virtual ICollection<ContactMethod> ContactMethods { get; set; }
public int FederalTaxID { get; set; }
public virtual Client Client { get; set; }
}
-
//MyDataContext.cs
[DbConfigurationType(typeof(MySqlEFConfiguration))]
public class MyDataContext : IdentityDbContext<ApplicationUser>
{
public MyDataContext()
: base("DataConnection")
{
}
static MyDataContext()
{
Database.SetInitializer(new DataInitializer());
}
public DbSet<Client> Clients { get; set; }
public DbSet<Organization> Organizations { get; set; } // Store Employer and OrgEntity
/// <summary>
/// Sets up unclear relationships between entities before the models are constructued in a database.
/// For example, models which extend other models must have their Ids mapped (because it is an
/// inherited member, and so is not found by Entity Framework by default)
/// </summary>
/// <param name="modelBuilder">the object responsible for constructing the database from code-first</param>
protected override void OnModelCreating(DbModelBuilder modelBuilder)
{
//set up parent organization relationship
modelBuilder.Entity<Organization>()
.HasOptional(n => n.ParentOrganization)
.WithMany(o => o.ChildOrganizations)
.Map(m => m.MapKey("ParentOrganization_Id"));
//set up the organization-employee assignment
modelBuilder.Entity<Employee>()
.HasOptional(a => a.OrganizationAssignment)
.WithMany(a => a.Employees);
//used to integrate Identity stuff into same db as Clients, etc.
modelBuilder.Entity<IdentityUserLogin>().HasKey<string>(l => l.UserId);
modelBuilder.Entity<IdentityRole>().HasKey<string>(r => r.Id);
modelBuilder.Entity<IdentityUserRole>().HasKey(r => new { r.RoleId, r.UserId });
}
}
-
<!--web.config-->
.
.
.
<connectionStrings>
<add name="DataConnection"
providerName="Mysql.Data.MysqlClient"
connectionString="server=localhost;user id=myid;password=mypass;persistsecurityinfo=True;database=app_db"/>
</connectionStrings>
.
.
.
From various other posts like this one , this one , and this one . I have tried many different things to get it to work. This includes commenting out my constructor for MyDbContext, changing the providerName attribute of my connection string to be "System.Data.SqlClient", changing the connection string name to be "DefaultConnection", removing my connection strings altogether, and combinations of all of these things. I make sure to rebuild between trying to add the Controller. However, after performing these different changes, I still receive the same error when I try to add a new Controller.
Generally, I can find all my questions already answered, but the answers don't seem to be working for me on this one. I think what might separate my case from the ones linked is that my DbContext is actually an instance of IdentityDbContext. I believe the constructor for IdentityDbContext just calls the base constructor for it, anyway, so I don't see how this could be much of an issue.
Any help is much appreciated. Thank you!
You didn't map your Employer entity to the model. That's why compiler is unable to retrieve metadata for Employer. Firstly, add DbSet as below and let me know, if does it work.
public DbSet<Client> Clients { get; set; }
public DbSet<Organization> Organizations { get; set; }
public DbSet<Employer> Employers { get; set; }

How should AutoMapper access my DAL?

I have an InvoiceInputModel with a ProjectId property which is a reference to a Project entity. Ideally, I want AutoMapper to be able to map an entire Invoice entity from an InvoiceInputModel, which looks like this:
public class InvoiceInputModel
{
public Guid Id { get; set; }
public DateTime Date { get; set; }
public string Reference { get; set; }
public Guid ProjectId { get; set; }
}
Obviously the following is bad:
Mapper.CreateMap<InvoiceInputModel, Invoice>()
.ForMember(src => src.Project, opt => opt.MapFrom(
dest => _unitOfWork.CurrentSession.Get<Project>(dest.ProjectId)
)
);
How do I tell AutoMapper that invoice.Project should be mapped to a Project entity based off of the ProjectId property in InvoiceInputModel while preserving loose coupling?
Invoice/Edit in my InvoiceController:
[HttpPost]
[Authorize]
public ActionResult Edit(InvoiceInputModel invoiceInputModel)
{
var invoice = _unitOfWork.CurrentSession.Get<Invoice>(invoiceInputModel.Id);
Mapper.Map<InvoiceInputModel, Invoice>(invoiceInputModel, invoice);
invoice.Project = _unitOfWork.CurrentSession.Get<Project>(invoiceInputModel.ProjectId);
// I want AutoMapper to do the above.
_unitOfWork.CurrentSession.SaveOrUpdate(invoice);
_unitOfWork.Commit();
return View(invoice);
}
I spotted something about "Resolvers" and ResolveUsing, but I have no experience using it.
How do I tell AutoMapper to do this while preserving loose coupling between my entity models, input models and view models? Or is there a better way?
How do I tell AutoMapper that invoice.Project should be mapped to a Project entity based off of the ProjectId property in InvoiceInputModel while preserving loose coupling?
You can't. If AutoMapper is going somewhere else to fetch data, then it's not loose coupled.
You're not modifying the Project in this particular View anyway - why do you need to set the relationship to Project, isn't nHibernate smart enough to see that property hasn't changed, and not do anything?
I personally have entities in viewmodels instead of IDs, so that binding happens automatically.
http://sprokhorenko.blogspot.com/2011/03/bind-to-entity-id.html

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