Entity Framework custom configuration

With EF Code-First it’s easy create a database starting from domain objects,
but it’s always possible create an our custom configuration.

In my project I have two class, Role and User:

public class Role
{
    public Guid Id { get; set; }
    public string Name { get; set; }
}

public class User
{
     IList<Role> _role;

     public virtual IList<Role> Roles
     {
        get { return _role ?? ( _role = new List<Role>() ); }
     }

     public Guid Id { get; set; }

     public string UserName{ get; set; }
     public string FirstName { get; set; }
     public string LastName { get; set; }
}

If you want create custom configuration for User and Role, you can write others two class that works as configuration, RoleConfigration and UserConfiguration that extend EntityTypeConfiguration:

// custom configuration for Role
public class RoleConfiguration : EntityTypeConfiguration<Role>
{
     public RoleMapping()
     {
         ToTable( "Roles" ); // ef will create a table with name Roles
         HasKey(o => o.Id);  // define a key
         Property( o => o.Name ).IsRequired(); // this property is required on repository
     }
}

// custom configuration for User
public class UserConfiguration : EntityTypeConfiguration<User>
{
    public UserMapping()
    {
         ToTable( "Users" ); // ef will create a table with name Users
         
         HasKey(o => o.Id);  // define a key
         // the property is required on repository
         Property( o => o.UserName ).IsRequired(); 
         // this property is nullable and map on column with name firstname
         Property( o => o.FirstName ).HasColumnName("firstname");
         // this property is nullable and map on column with name lastname
         Property( o => o.LastName ).HasColumnName("lastname"); 

         // configure many-to-many navigation property between
         // User and Role
         HasMany( o => o.Roles ).WithMany();
    }
}

Now, for use our custom configuration, we will simply add RoleConfiguration and UserConfiguration to DbContext:

public class MyDbContext : DbContext
{
    public virtual IDbSet CreateSet()
         where TEntity : class
    {
        return Set();
    }

    protected override void OnModelCreating( DbModelBuilder modelBuilder )
    {
        modelBuilder.Configurations.Add( new RoleConfiguration() );
        modelBuilder.Configurations.Add( new UserConfiguration() );

        base.OnModelCreating( modelBuilder );
    }
}

Hope this helps,
Tony

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