Where are Entity Framework Core conventions?

问题

using EF 6.1+ there were times where we need to add or remove existing conentions. The code looks more or less like:

public class MyContext : DbContext
    {
            protected override void OnModelCreating(DbModelBuilder modelBuilder)
            {
                modelBuilder.Conventions.AddFromAssembly(Assembly.GetExecutingAssembly());
                modelBuilder.Conventions.Remove<PluralizingTableNameConvention>();
                modelBuilder.Conventions.Remove<OneToManyCascadeDeleteConvention>();
                modelBuilder.Conventions.Remove<ManyToManyCascadeDeleteConvention>();

                base.OnModelCreating(modelBuilder);
            }
}

how do the same in EF core? Modelbuilder has no Conventions property :(

回答1:

I'm porting some code from EF to EF Core 2.1+ and can't wait for EF Core 3.0 so wrote a few extension methods which help a bit..

public static IEnumerable<IMutableEntityType> EntityTypes(this ModelBuilder builder)
{
    return builder.Model.GetEntityTypes();
}

public static IEnumerable<IMutableProperty> Properties(this ModelBuilder builder)
{
    return builder.EntityTypes().SelectMany(entityType => entityType.GetProperties());
}

public static IEnumerable<IMutableProperty> Properties<T>(this ModelBuilder builder)
{
    return builder.EntityTypes().SelectMany(entityType => entityType.GetProperties().Where(x => x.ClrType == typeof(T)));
}

public static void Configure(this IEnumerable<IMutableEntityType> entityTypes, Action<IMutableEntityType> convention)
{
    foreach (var entityType in entityTypes)
    {
        convention(entityType);
    }
}

public static void Configure(this IEnumerable<IMutableProperty> propertyTypes, Action<IMutableProperty> convention)
{
    foreach (var propertyType in propertyTypes)
    {
        convention(propertyType);
    }
}

with these you can write conventions similar to those in EF 6.1.x, for example.

// equivalent of modelBuilder.Conventions.Remove<PluralizingTableNameConvention>();
modelBuilder.EntityTypes()
            .Configure(et => et.Relational().TableName = et.DisplayName());

// Put the table name on the primary key
modelBuilder.Properties()
            .Where(x => x.Name == "Id")
            .Configure(p => p.Relational().ColumnName = p.DeclaringEntityType.Name + "Id");

// Mark timestamp columns as concurrency tokens
modelBuilder.Properties()
            .Where(x => x.Name == "Timestamp")
            .Configure(p => p.IsConcurrencyToken = true);

For EF Core 3.0 the metamodel methods have changed slightly so you need

modelBuilder.EntityTypes()
            .Configure(et => et.SetTableName(et.DisplayName()));

modelBuilder.Properties()
            .Where(x => x.Name == "Id")
            .Configure(p => p.SetColumnName(BaseName(p.DeclaringEntityType.Name) + "Id"));

Haven't checked this for efficiency but unless your model is huge it shouldn't pose a problem

This can be extended with other helpers for foreign keys, indexes etc

回答2:

Looks like it's still not in EF Core 2.0. So here's one way of achieving it. I had done this to apply consistent behaviour to certain attributes, but to address the examples in your question you could try this:

protected override void OnModelCreating(ModelBuilder modelBuilder)
{
    // equivalent of modelBuilder.Conventions.AddFromAssembly(Assembly.GetExecutingAssembly());
    // look at this answer: https://stackoverflow.com/a/43075152/3419825

    // for the other conventions, we do a metadata model loop
    foreach (var entityType in modelBuilder.Model.GetEntityTypes())
    {
        // equivalent of modelBuilder.Conventions.Remove<PluralizingTableNameConvention>();
        entityType.Relational().TableName = entityType.DisplayName();

        // equivalent of modelBuilder.Conventions.Remove<OneToManyCascadeDeleteConvention>();
        // and modelBuilder.Conventions.Remove<ManyToManyCascadeDeleteConvention>();
        entityType.GetForeignKeys()
            .Where(fk => !fk.IsOwnership && fk.DeleteBehavior == DeleteBehavior.Cascade)
            .ToList()
            .ForEach(fk => fk.DeleteBehavior = DeleteBehavior.Restrict);
    }

    base.OnModelCreating(modelBuilder);
}

You should be able to do a lot of things with entityType

来源：https://stackoverflow.com/questions/46837617/where-are-entity-framework-core-conventions

标签

entity-framework-core