Question

I’m quite new to using the entity framework and I’m having trouble getting my head around how to write a query that uses a many to many relationship. I have 3 entities. Role, User and Securable. A Role can have multiple Securables, and a Securable can be assigned to many Roles. A Role can have multiple Users, and a User can have multiple Roles.

My Question is: How would I go about writing a query that gave me a distinct list of Securables for a given user ID?

Here is my model, where EF automatically creates the link tables for me.

public class SecurityContext : DbContext
{
    public DbSet<User> Users { get; set; }

    public DbSet<Role> Roles { get; set; }

    public DbSet<Securable> Securables { get; set; }
}

public class User 
{
    public Guid UserId { get; set; }

    public string Forename { get; set; }

    public string Surname { get; set; }

    public string Username { get; set; }

    public string Password { get; set; }

    public virtual ICollection<Role> Roles { get; set; }
}

public class Securable
{
    public Guid SecurableId { get; set; }

    public string Name { get; set; }

    public virtual ICollection<Role> Roles { get;set;}
}

public class Role
{
    public Guid RoleId { get; set; }

    public string Name { get; set; }

    public virtual ICollection<Securable> Securables { get; set; }

    public virtual ICollection<User> Users { get; set; }
}

Answer 1

Untested, but off the top of my head it would be something like this:

var context = new DbContext();
var result = context.Securables
                    .Where(s => s.Roles
                                 .Any(r => r.Users
                                            .Any(u => u.UserId = userId)))
                    .Distinct();