DataAccess layer, Model layer and POCO classes with Code First Entity Framework

Question

I’m following the suggested architectural path put forward in “Programming Entity Framework Code First”.

There is a DataAccess layer and a Model layer which both form separate projects in VS.

The Model layer holds my classes for business objects. The DataAccess layer has a reference to the Model project so that it can create a context and DbSets for each of my business objects.

The issue is that some classes in the Model need to access the data layer to perform calculations, however I cannot reference the DataAccess layer in my Model project as it will create a circular reference. The DataAccess layer must reference the Model layer so that it can create the DbSets. Please also note the calculations are read only – only getters, which are not persisted to the database.

I’ve been searching for hours on this and have found useful information but I think I’m missing something simple? POCO classes are meant to be simple, but my classes represent things that have some very related but more complicated calculations.

As a simple concrete example I have a Transaction class and an AccountBalance class. The Transaction class needs to know the AccountBalance on specific dates for display purposes – such as percentage change (this is just a simple example):

public class Transaction

{
    public DateTime Date { get; set; }
    public string Description { get; set; }    
        ... etc    
    public double PercentageChange
    {
        get
        {
            // return TransactionAmount / AccountBalance on TransactionDate    
            //  however Transaction has no knowledge of AccountBalance... 
         }
    }
}

Thanks

Leon Cullens · Accepted Answer · 2012-11-24 01:00:12Z

2

Personally I would NOT place the business logic in my POCOs. Imho you need to create a separate service layer (or whatever you call it) and place the business logic there. The POCOs should really be simple objects without any business logic.

So your architecture will look like this:

GUI -> Service Layer -> Data Access Layer (Repositories?) -> Database.

Now all your projects can reference your model layer.

answered Nov 24, 2012 at 1:00

Leon Cullens

12.5k11 gold badges56 silver badges87 bronze badges

Sign up to request clarification or add additional context in comments.

1 Comment

user1622713 Over a year ago

Thanks @Leon. Sounds good but I am missing something still. That alleviates the access issue, but I want to have a class that has all of the required properties in it (such as PercentageChange above). I can do that by making public class TransactionService : Transaction and adding my properties in... But the data is still tied to Transaction isn't it? If I use _Context.Transactions.ToList() I won't have access to my new properties etc. If I make additional logic to get a list of Transactions in my TransactionsService class I'm defeating the purpose of using EF... Im confused, thanks for help

Collectives™ on Stack Overflow

DataAccess layer, Model layer and POCO classes with Code First Entity Framework

1 Answer 1

1 Comment

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

1 Comment

Your Answer

Sign up or log in

Post as a guest

Related