实体框架中的模型关系

Question

I'm trying to build some models based on a database, i have two tables, one for workers and other is for branches. Every worker works in a branch, so every worker has only one branch and branches has unlimited workers.

My worker model:

public class Worker
{
    public Worker()
    {
        Overhours = new List<Overhour>();
    }

    [DatabaseGenerated(DatabaseGeneratedOption.Identity)]
    public decimal WorkerId { get; set; }
    public decimal BranchId { get; set; }
    .....
    public virtual Branch Branch { get; set; }
    .....
}

Branches:

public class Branch
{
    public Branch()
    {
        Workers = new List<Worker>();
    }

    [Key]
    [DatabaseGenerated(DatabaseGeneratedOption.Identity)]
    public decimal BranchId { get; set; }
    [Required(AllowEmptyStrings = false, ErrorMessage = "Bir şube adı girmelisiniz.")]
    public string BranchName { get; set; }
    public virtual ICollection<Worker> Workers { get; set; }
}

Here is the problem, i can access a workers branch using m.Workers.Find(Id).Branch but i want to access all workers working in a branch. So i want something like m.Branches.Find(Id).Workers . It works but it seems weird to me. Because a worker object has already all branches in it also branch object has all workers too. I don't even know i need this because i can easily get all workers who's working in a branch by using LINQ to Entity or raw SQL.

What's the right way to do it?

Answer 1

The navigation properties ( Branch in Worker class and Workers in Branch ) are lazy loaded. When you fetch a Worker from the database, it does not include the branch in it. But whenever you need the branch (that is, when you read w.Branch ) the lazy loading mechanism kicks in and fetches it from the database. This is also true for Workers in Branch .

So as a simple answer, you're doing it the right way.

BTW, there are lots of things to learn here:

• you can use eager loading to fetch everything you need in a single call to the DB
• you can turn off lazy loading, if you know you don't need related data it some parts of your code.
• You can load some workers and then some branches and EF will connect them in case they are logically connected. In some scenarios this might be faster than using lazy loading.