Suggestion for documentation - Partial classes for your dbContext

[ChristineBoersen]

Something you may want to recommend in the documentation, especially for complex data models, is using a Partial Class for you dbContext class.

By using a pattern such as this, you can keep all the builder logic for your model with your POCO so it is easier to work on in a team environment (low concurrency issue with your MyContext.cs file).

In file Address.cs

public class Address
{

    public Address()
    {

        BusinessAddresses = new HashSet<BusinessAddress>();
        PersonAddresses = new HashSet<PersonAddress>();
        TransactionAddresses = new HashSet<TransactionAddress>();

    }

    public Int64 AddressID { get; set; }
    public string AddressLine1 { get; set; }
    public string AddressLine2 { get; set; }
    public string City { get; set; }
    public string State { get; set; }
    public string PostalCode { get; set; }
    public string County { get; set; }
    public string Country { get; set; }

    public bool Active { get; set; }
    [Timestamp]
    public byte[] RowVersion { get; set; }

    public virtual ICollection<BusinessAddress> BusinessAddresses { get; set; }
    public virtual ICollection<PersonAddress> PersonAddresses { get; set; }
    public virtual ICollection<TransactionAddress> TransactionAddresses { get; set; }


}

public partial class MyContext
{
    public virtual DbSet<Address> Address { get; set; }

    protected void Address_CreateObject()
    {
        _ModelBuilder.Entity<Address>(entity =>
        {

            entity.Key(e => e.AddressID).SqlServerClustered();
            entity.Property(e => e.AddressID).UseSqlServerIdentityColumn();

            // Put your fields here for any additional building



            entity.Property(e => e.Active).Required().HasSqlServerDefaultValue(true);

            entity.Property(e => e.RowVersion).ConcurrencyToken();



        });

    }

}

And then in your "main" dbContext partial class, you just add the one line of code, Address_CreateObject() in this case for it to call your builder code in the Address.cs file's MyContext partial class.

MyContext.cs

public partial class MyContext: dbContext
{

    protected ModelBuilder _ModelBuilder { get; set; }

    protected override void OnModelCreating(ModelBuilder modelBuilder)
    {
        _ModelBuilder = modelBuilder;      

        Address_CreateObject();

        base.OnModelCreating(modelBuilder);


    }


}

[Maverik]

Nice suggestion. I was wondering how to do this and now I see what I was missing. Thanks!

[ChristineBoersen]

Glad I could help, I hope the idea helps others as well :)

[rowanmiller]

Partial classes is one way to do this. Another option is just having static methods that they can call from within OnModelCreating. Ultimately we are going to enable a pattern like the EntityTypeConfiguration<T> from EF6 (tracked by #2805).

Bottom line is that there are lots of ways to organize code and we don't think we need specific docs about how to organize the code in OnModelCreating.

[rebeccapowell]

What we be really useful would be to make void OnModelCreating(ModelBuilder modelBuilder) a partial method.

If you are doing DbFirst and recreating the DbContext, it means that any custom OnModelCreating code can be split into a partial class / partial method and the code added to the partial method won't be lost. Currently, after rescaffolding you lose anything custom inside the OnModelCreating override to the underlying DbContext OnModelCreating.