Entity Framework 4 POCO, Repository and Specification Pattern [Upgraded to CTP5]

Before reading this, you might want to read these two posts first:

• Entity Framework 4 POCO, Repository and Specification Pattern: this post explained an implementation of a data access layer on top of Entity Framework using code first development with POCO, Repositiory and Specification Pattern
• Specification Pattern in Entity Framework 4 Revisited: this post addressed a problem of the Specification patten being implemented in the earlier post and also proposed a solution to fix that problem

You might have been aware that MS just released Entity Framework 4 CTP5 some days ago. There have been some comments asking me when the data access layer would be upgraded to that version. Since I had been quite busy these days,  the answers for these questions was just a promise that I would do the upgrade when I had time after I finished investigating the new release carefully. However, some readers seem to be anxious waiting for the code updated so they keep asking me for the progress (and I feel good because I know there are some ones who are interested in the framework I built :)).

So, today I decided to fulfill my promise: the source code has been updated in google code. You can download the latest version (1.3 at this  writing) here http://code.google.com/p/ef4prs/downloads/list

Note: to be able to compile the code, you must first download and install EF4 CTP5.

Some implementation notes:

– The assembly is now changed to EntityFramework.dll and located at C:\Program Files (x86)\Microsoft ADO.NET Entity Framework Feature CTP5\Binaries\EntityFramework.dll

– Base mapping class has changed from EntityConfiguration<T> to EntityTypeConfiguration<T>

– Entity Framework team seems to concentrate on implementing DbContext much more than ObjectContext. But if you want to access to ObjectContext from DbContext, here is the way:

ObjectContext ctx = ((IObjectContextAdapter)_dbContext).ObjectContext;

– We do not need to register entity any more, just add mapping class(es) to the ModelBuilder then we are all set. Well, this is for your information only, since this framework will do this automatically in the XContextBuilder class.

– The most and important thing, I think, is EF now will automatically map entity relationships without explicitly writing the mapping code. For example:

I have an entity Customer that has many Orders. These two classes will be defined as below:

public class Customer : Entity
{
    public Customer()
    {
        Orders = new List<Order>();
    }

    public virtual string Firstname
    {
        get; set;
    }

    public virtual string Lastname
    {
        get; set;
    }

    public virtual IList<Order> Orders
    {
        get;
        set;
    }

    public virtual DateTime Inserted
    {
        get; set;
    }
}

public class Order : Entity
{
    public Order()
    {
        OrderLines = new List<OrderLine>();
    }

    public virtual IList<OrderLine> OrderLines
    {
        get;
        set;
    }

    public virtual DateTime OrderDate
    {
        get; set;
    }

    public virtual Customer Customer
    {
        get; set;
    }
}

Here is the mapping classes:

public class CustomerMapping : EntityTypeConfiguration<Customer>
{
    public CustomerMapping()
    {
        HasKey(x => x.Id);

        Property(x => x.Firstname).IsRequired().HasMaxLength(25);
        Property(x => x.Lastname).IsRequired().HasMaxLength(25);
        Property(x => x.Inserted);

        //we dont need to write this code to specify the relationship, this will autolatically done by EF
        //HasMany(x => x.Orders).WithRequired(y => y.Customer).HasForeignKey(c => c.CustomerId);

        ToTable("Customer");
    }
}

public class OrderMapping : EntityTypeConfiguration<Order>
{
    public OrderMapping()
    {
        HasKey(x => x.Id);

        Property(x => x.OrderDate);

        // No need to write mapping code to Customer
        //HasRequired(c => c.Customer);

        ToTable("Order");
    }
}

With these mappings, EF will generate the Order table with a foreign key to Customer table as below:

You can download and check out the test code to see other mapping scenarios like many-to-many or how to change the table name in the mapping code.

Happy coding!