将IEntityTypeConfiguration与基本实体一起使用

Question

在EF Core 2.0中,我们能够从IEntityTypeConfiguration更清晰的Fluent API映射(源代码)派生.

如何扩展此模式以使用基础实体？在下面的示例中,我如何才能BaseEntityConfiguration减少重复,LanguageConfiguration并MaintainerConfiguration修改BaseEntity仅在BaseEntityConfiguration？中的属性？这样的BaseEntityConfiguration样子会是什么样的; 如果有的话,如何使用OnModelCreating()？请参阅示例末尾附近的TODO代码.

例:

public abstract class BaseEntity
{
    public long Id { get; set; }
    public DateTime CreatedDateUtc { get; set; }
    public DateTime? ModifiedDateUtc { get; set; }
}

public class Language : BaseEntity
{
    public string Iso6392 { get; set; }
    public string LocalName { get; set; }
    public string Name { get; set; }
}

public class Maintainer : BaseEntity
{
    public string Email { get; set; }
    public string Name { get; set; }
}

public class FilterListsDbContext : DbContext
{
    public FilterListsDbContext(DbContextOptions options) : base(options)
    {
    }

    public DbSet<Language> Languages { get; set; }
    public DbSet<Maintainer> Maintainers { get; set; }

    protected override void OnModelCreating(ModelBuilder modelBuilder)
    {
        //TODO: Possibly add something like BaseEntityConfiguration?
        modelBuilder.ApplyConfiguration(new LanguageConfiguration());
        modelBuilder.ApplyConfiguration(new MaintainerConfiguration());
    }
}

public class LanguageConfiguration : IEntityTypeConfiguration<Language>
{
    public void Configure(EntityTypeBuilder<Language> entityTypeBuilder)
    {
        //TODO: Move this to something like BaseEntityConfiguration?
        entityTypeBuilder.Property(b => b.CreatedDateUtc).HasDefaultValueSql("CURRENT_TIMESTAMP");
    }
}

public class MaintainerConfiguration : IEntityTypeConfiguration<Maintainer>
{
    public void Configure(EntityTypeBuilder<Maintainer> entityTypeBuilder)
    {
        //TODO: Move this to something like BaseEntityConfiguration?
        entityTypeBuilder.Property(b => b.CreatedDateUtc).HasDefaultValueSql("CURRENT_TIMESTAMP");
    }
}

Answer 1

这样的东西可以工作(未经测试)？

public abstract class BaseEntityTypeConfiguration<TBase> : IEntityTypeConfiguration<TBase>
    where TBase : BaseEntity
{
    public virtual void Configure(EntityTypeBuilder<TBase> entityTypeBuilder)
    {
        //Base Configuration
    }
}

public class MaintainerConfiguration : BaseEntityTypeConfiguration<Maintainer>
{
    public override void Configure(EntityTypeBuilder<Maintainer> entityTypeBuilder)
    {
        entityTypeBuilder.Property(b => b.CreatedDateUtc).HasDefaultValueSql("CURRENT_TIMESTAMP");
        base.Configure(entityTypeBuilder);
    }
}

Answer 2

还有一种方法可以解决这个问题，那就是使用模板方法设计模式。像这样：

public abstract class BaseEntityTypeConfiguration<TBase> : IEntityTypeConfiguration<TBase>
    where TBase : BaseEntity
{
    public void Configure(EntityTypeBuilder<TBase> entityTypeBuilder)
    {
        //Base Configuration

        ConfigureOtherProperties(builder);
    }

    public abstract void ConfigureOtherProperties(EntityTypeBuilder<TEntity> builder);
}

public class MaintainerConfiguration : BaseEntityTypeConfiguration<Maintainer>
{
    public override void ConfigureOtherProperties(EntityTypeBuilder<Maintainer> entityTypeBuilder)
    {
        entityTypeBuilder.Property(b => b.CreatedDateUtc).HasDefaultValueSql("CURRENT_TIMESTAMP");        
    }
}

通过这种方式，您无需在子配置中编写任何一行。