LINQ ASP.NET MVC存储库模式的最佳实践是什么

Question

I'm a junior web developer trying to learn more every day.

What it the best practice for you guys to performe MVC repository pattern with Linq?

The one I use:

Create extra clases with the exact name of my .tt files with CRUD method like getAll(), getOne(), Update(), Delete() filling my own class with the entity framework and returning this, or using the entity framework crude

this is an example of what I'm actually doing.

this is my getAll method of my class for example User

public class CEmployee : CResult
{

    public string name{get;set;}
    public string lastname{get;set;}
    public string address{get;set;}

    //Extracode
    public string Fullname // this code is not in the .tt or database
    {
        get
        {
            return name + lastname;
        }
    }

    public <List>CEmployee getAll()
    {
        try
            {
                var result = (from n in db.Employee 
                                select new CEmployee // this is my own class I fill it using the entity
                                {
                                    name = n.name,
                                    lastname = n.lastname,
                                    address = n.address
                                }).ToList();

                                if (result.Count > 0)
                                {
                                    return result;
                                }
                                else
                                {
                                    return new List<CResult>
                                    {
                                        new CResult
                                        {
                                            has_Error = true,
                                            msg_Error = "Element not found!!!!"
                                        }
                                    }
                                }

            }
        catch
            {
                return Exception();
            }


    }
}

that the way I do all thing I return a filled of my type, but on the web I see that people return the entity type normaly, But I do this to manipulate my response, And if I want to return extra information I just have to neste a list for example, whats the best way guys, return mytype or return the entity type ?

PD, I also use this class like my ViewModel.And I do this for all my classes.

Answer 1

One of the projects I am currently one uses Dependency Injection to setup the DAL (Data Access Layer.) We also are using an n-Tier approach; this separates the concern of the repository from the Business Logic and Front End.

So we would start with 4 or so base projects in the application that link to each other. One of that handles the Data Access, this would be your repository; read up on Ninject for more info on this. Our next tier is our Domain which houses the Entities built by the t4 template(.tt files) and also our DTO's (data transfer objects which are flat objects for moving data between layers.) Then we have a service layer, the service layer or business logic layer holds service objects that handle CRUD operations and any data manipulation needed. Lastly we have our front end which is the Model-View-ViewModel layer and handles the controllers and page building.

The MVVM calls the services, the service objects call the data access layer and Entity Framework works with Ninject to access the data and its stored in the DTO's as it is moved across layers.

Now this may seem overly complex depending on the application you are writing, this is built for a highly scalable and expandable web application.

Answer 2

I would highly recommend going with a generic repository implementation. The layers between your repository and the controller vary depending on a number of factors (which is kind of a broader/bigger topic) but the generic repository gets you going on a good implementation that is lightweight. Check out this article for a good description of the approach:

http://www.asp.net/mvc/tutorials/getting-started-with-ef-5-using-mvc-4/implementing-the-repository-and-unit-of-work-patterns-in-an-asp-net-mvc-application

Answer 3

Ideally in a MVC application, you will want to repositories in a different layer like in a separate project, let's call it Data layer.

You will have an IRepository interface that contain generic method signatures like GetAll, GetById, Create or UpdateById. You will also have abstract RepositoryBase class that contain shared implementation such as Add, Update, Delete, GetById, etc.

The reason that you use an IRepository Interface is, there are contracts for which your inherited repository class, such as EmployeeRepository in your case, need to provide concrete implementations. The abstract class serves as a common place for your shared implementation (and override them as you need to).

So in your case, what you are doing using LINQ with your DbContext is basically correct, but implementation like your GetAll method should be part of the generic/shared implementation in your abstract class RepositoryBase:

public abstract class RepositoryBase<T> where T : class
{
    private YourEntities dataContext;
    private readonly IDbSet<T> dbset;

    protected RepositoryBase(IDatabaseFactory databaseFactory)
    {
        DatabaseFactory = databaseFactory;
        dbset = DataContext.Set<T>();
    }

    protected IDatabaseFactory DatabaseFactory
    {
        get;
        private set;
    }

    protected YourEntities DataContext
    {
        get { return dataContext ?? (dataContext = DatabaseFactory.Get()); }
    }
    public virtual T GetById(long id)
    {
        return dbset.Find(id);
    }
    public virtual T GetById(string id)
    {
        return dbset.Find(id);
    }
    public virtual IEnumerable<T> GetAll()
    {
        return dbset.ToList();
    }
}

I would suggest you need to think about whether or not to return an error result object like CResult, and think about if your CEmployee and CResult should exist in this parent-child relationship. Also think about what you want to do with your CResult Class. It seems to me your CEmployee handles too many tasks in this case.