Entity Framework DbSet Discover What is a DbSet and How to Use it

In Entity Framework, the DbSet class represents an entity set that can be used for the database operation, such as create, read, update, and delete.

• The context class must include the DbSet type properties for the entities which map to database tables and views.
• The DbSet is an implementation of the Repository pattern.

public class BookStore : DbContext
{
    public BookStore() : base(FiddleHelper.GetConnectionStringSqlServer())
    {
    }

    public DbSet<Author> Authors { get; set; }
}

public class Author
{
    public int AuthorId { get; set; }
    public string FirstName { get; set; }
    public string LastName { get; set; }
}

Methods

The following are the most commonly used methods.

Add

• It adds the given entity to the context in the Added State.
• These entities are inserted into the database table when the SaveChanges on the context is called.

AddRange

• It adds the collection of entities to the context.
• All the entities in the collection are marked as Added State.
• All the entities are inserted into the database table when the SaveChanges on the context is called.
• All the entities that are already in the context in some other state will have their state set to Added.

Attach

• It attaches the given entity to the context.
• State of the attached will be marked as Unchanged.
• It means calling Savechanges on the context will not affect the database

AsNoTracking()

• It is an extension method where the returned entities are not be tracked by the context.
• It means that if you want to save the entities, you need to attach them to the context and set the state correctly.

Create()

• It creates and returns a new instance of an entity.
• This entity is not added or attached to set.

Find

• It finds and returns an entity with the given primary key values.
• Context always looks for the entity in the context first and returns it if found.
• If it is not found, then a request is sent to the database.
• The entity if not found then the null is returned.

Include(String)

• Specifies the related objects to include in the query results.

Remove

• It is used to delete the entity from the database.
• The entity is not removed immediately, and they are marked as deleted.
• The entity is Deleted from the database when SaveChanges is called.

RemoveRange

• It is used to delete the collection of entities.
• It does so by changing the state of entities to the deleted state.
• When the SaveChanges method is invoked, Context will delete these entities from the database

SQLQuery

• It uses the raw SQL query to return the entities.
• It has two parameters.
  • The First Parameter is the SQL query string.
  • The second is the parameters to apply to the SQL query.