Question

Models:

 public class User
 {
     [Key]
     public int UserId { get; set; }
     public string UserName { get; set; }
 }

public class Resource
{
    [Key]
    public int ResourceId { get; set; }
    public string ResourceName { get; set; }
    public string  ResourceDescription { get; set; }
}

public class UserResource
{
    [Key, Column(Order=0)]
    public int UserId { get; set; }
    [Key, Column(Order=1)]
    public int ResourceId { get; set; }
    public int ResourceQuantity { get; set; }
}

I want to select “ResourceName” from Resource model and “ResourceQuantity” from UserResource model for a given “UserId”. Also, once selected, do I need a brand new model to carry only those two specified columns?

Also note that UserResource model has a composite key so I am confused as to how to make the join… Is this right?

 var userResources =
          from r in imDB.Resources
          join ur in imDB.UserResources
          on r.ResourceId equals ur.ResourceId
          select new { r.ResourceName, ur.ResourceQuantity };

Answer 1

Hence you’re using Code first you can create your models are as below by using EF conventions.

public class User {
    public int Id { get; set; }
    public string UserName { get; set; }

    public virtual ICollection<Resource> Resources { get; set; }
   }

public class Resource {
    public int Id { get; set; }
    public string ResourceName { get; set; }
    public int ResourceQuantity { get; set; }

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

Then EF will generate your junction table is as UsersResources.You don’t need to create additional model as you did.EF will look after that.

When using POCOs with EF, if you mark your navigation properties as
virtual you can use additional EF supports like Lazy Loading. So in
general use a virtual keyword in navigation properties considered to
be a good practice.

UPDATE

You may try something like below:

Method 1 : Method based syntax

imDB.Resources.Where(r => r.Users.Any(u => u.UserId == userId))

Method 2 : Query based syntax

from r in imDB.Resources
from u in r.Users
where u.UserId == userId
select r;

I hope this will help to you.