如何在实体框架中使用链接表

Question

I've been trying to puzzle out how to use entity framework to return a query like so

{
  UserID: 1,
  Roles: ["RoleOne","RoleTwo","RoleThree"]
}

Where my tables are as such:

    public class User
    {
        public int? ID { get; set; }
        public string? FirstName { get; set; }
        public string? LastName { get; set; }
    }

    public class UserRoles
    {
        public int ID { get; set; }
        public int UserID{ get; set; }
        public int RoleID { get; set; }
    }

    public class Roles
    {
        public int ID { get; set; }
        public string? Name { get; set; }
    }

I've tried joins, and looked into creating a relationship in the classes, as well as trying to figure out groupBy, but all with no luck.

If I'm missing something obvious please let me know! Thanks!

Answer 1

Your response model should be like this:

public class RespModel
{
    public int UserID { get; set; }
    public List<string> Roles { get; set; }
}

And your query could be like this:

 var query = from userRolesRec in _context.UserRoles
             join user in _context.User on userRolesRec.UserID equals user.ID ?? 0
             select new RespModel
             {
               UserID = user.ID,
               Roles = (from roles in _context.Roles 
                        where userRolesRec.RoleID == roles.ID
                        select roles.Name).ToList()
             }