ViewModel for multiple tables without links between tables - asp.net-mvc

Question

I'm trying to write a View Model in an ASP.NET MVC5 project to show data from different tables on a form that the user can then edit and save. I'm using the following :-
VS 2017, c#, MySQL Database, Entity Framework 6.1.3, MySQL Connector 6.9.9, Code First from Database (existing database that I can't change)
To complicate matters, there are no links between the tables in the database, so I cannot work out how to create a suitable View Model that will then allow me to save the changes.
Here are the 4 table models :-
public partial class evc_bearer
{
[Key]
[Column(Order = 0]
[DatabaseGenerated(DatabaseGeneratedOption.None)]
public long evcid { get; set; }
[Key]
[Column(Order = 1]
[DatabaseGenerated(DatabaseGeneratedOption.None)]
public long bearerid { get; set; }
public int vlan { get; set; }
[Column("ref")]
public string _ref { get; set; }
[Required]
public string port { get; set; }
[Required]
public string endpoint { get; set; }
}
public partial class bearer
{
[Key]
public long id { get; set; }
[Column("ref")]
[Required]
public string _ref { get; set; }
public string name { get; set; }
public long? site { get; set; }
public long? provider { get; set; }
public long? mtu { get; set; }
public float? rental { get; set; }
public int? offsiteprovider { get; set; }
public float? offsiteproviderrental { get; set; }
public bool? aend { get; set; }
public int? equipmentport { get; set; }
public string orderref { get; set; }
public string offsiteref { get; set; }
public string notes { get; set; }
public float? bookingfactor { get; set; }
}
public partial class evc
{
[Key]
public long id { get; set; }
[Required]
public string type { get; set; }
public byte servicetype { get; set; }
public byte cos { get; set; }
public int cir { get; set; }
public int pir { get; set; }
public bool burst { get; set; }
[Column("ref")]
public string _ref { get; set; }
public string orderref { get; set; }
public byte state { get; set; }
public string notes { get; set; }
public float? rental { get; set; }
}
public partial class evc_provider
{
[Key]
public long id { get; set; }
[Required]
public string provider { get; set; }
}
This is the View Model I tried writing :-
public partial class evcBearersVM
{
[Key]
[Column(Order = 0)]
public long evcid { get; set; }
[Key]
[Column(Order = 1)]
public long id { get; set; }
[Column("ref")]
public string b_ref { get; set; }
public string b_name { get; set; }
public string ep_provider { get; set; }
public int eb_vlan { get; set; }
public string eb_port { get; set; }
public string eb_endpoint { get; set; }
}
This is the Linq query I used to populate the View Model :-
IQueryable<evcBearersVM> data = from eb in csdb.evc_bearers
join b in csdb.bearers on eb.bearerid equals b.id
join ep in csdb.evc_providers on b.provider equals ep.id
join e in csdb.evcs on eb.evcid equals e.id
where (eb.evcid == evcid && b.id == id)
select new evcBearersVM
{
evcid = eb.evcid,
id = b.id,
b_ref = b._ref,
b_name = b.name,
ep_provider = ep.provider,
eb_vlan = eb.vlan,
eb_port = eb.port,
eb_endpoint = eb._ref
};
So the query works and joins the tables to get the data I need and I can display this date in various views as needed. What I now need to do is be able to edit a row and save it back to the database. I have an Edit View that is showing the data I need but I'm not sure how to save changes given that it's a View Model and the DB Context isn't aware of it. Grateful for any help.

Answer 1

What you should do is, use the same view model as your HttpPost action method parameter and inside the action method, read the entities you want to udpate using the Id's (you can get this from the view model, assuming your form is submitting those) and update only those properties you need to update.
[HttpPost]
public ActionResult Edit(evcBearersVM model)
{
var b = csdb.bearers.FirstOrDefault(a=>a.id==model.id);
if(b!=null)
{
b.name = model.b_name;
b._ref = model.b_ref;
csdb.SaveChanges();
}
// Update the other entity as well.
return RedirectToAction("Index");
}