IT:AD:EF/CodeFirst:HowTo:Define Models/Properties

Examples: Properties

The following just specify contraints on size, key, etc.

It's done automatically if you the fieldname is called Id or TheEntitityId, but if you can't use that field name:

modelBuilder.Entity<Manager>()
  .HasKey(ma => ma.ManagerCode);

Use an anonymous object:

modelBuilder.Entity<Department>()
  .HasKey(t => new { t.DepartmentID, t.Name });

modelBuilder.Entity<Manager>().Property(ma => ma.Name)
  .HasMaxLength(20);

modelBuilder.Entity<Department>().Property(dp => dp.Name)
  .IsRequired();

You can ignore calculated columns:

modelBuilder.Entity<Department>().Ignore(t => t.Budget);

modelBuilder.Entity<Department>().Property(t => t.Name)
  .HasColumnName("DepartmentName");

MUST: mark Scalar Properties as virtual to enable improved Change Tracking (by going from Snapshot CT to Proxy POCO Change Tracking, which is based on IPOCO/IEntityWithChangeTracker).
MUST: mark Collection Navigation Properties as virtual to enable lazy loading.
MUST: Navigation Collection properties must implement ICollection<Entities>
SHOULD: As we are working with proxies, can use private set for Id, etc:
- public string Id {get; private set;}
CONSIDER: For properties that need to ignored:
- DataAnnotations: [Ignore] (see IT:AD:Code First:DataAnnotations).
- FluentAPI: within DataContext.OnModelCreating(): modelBuilder.Entity<Department>().Ignore(t => t.Budget); (see IT:AD:Code First:FluentAPI:Properties)
CONSIDER: For derived calculated properties that need to be saved, use empty sets:
- public FullName {get {return _first + " " + _last;} set {}}
  * CONSIDER: If you have to turn of Id autogeneration:
- DataAnnotations: ? (see IT:AD:Code First:DataAnnotations)
- FluentAPI: within DataContext.OnModelCreating(): modelBuilder.Entity<Dept>().Property(t => t.ID).HasDatabaseGeneratedOption(DatabaseGeneratedOption.None); (see IT:AD:Code First:FluentAPI:Properties)