Should data access operations be encapsulated in the ViewModel or Controller? - entity-framework

Question

One of the main reasons I want to use a ViewModel instead of the model direct in the controller is that I notice the controller containing data access that, to me, seems to be the wrong place for this work. Shouldn't data access / read write be done in the ViewModel?
things like:
Data Access
Read / Write
Mapping
Select Lists
i.e.
EF created Model:
//------------------------------------------------------------------------------
// <auto-generated>
// This code was generated from a template.
//
// Manual changes to this file may cause unexpected behavior in your application.
// Manual changes to this file will be overwritten if the code is regenerated.
// </auto-generated>
//------------------------------------------------------------------------------
namespace TestIODSManagement.Models
{
using System;
using System.Collections.Generic;
public partial class ClientJob
{
public int Id { get; set; }
public int ClientId { get; set; }
public int JobTypeId { get; set; }
public string OlapAppName { get; set; }
public string EdgeAppName { get; set; }
public Nullable<int> DatabaseServer { get; set; }
public Nullable<int> ProcessingServer { get; set; }
public Nullable<int> QueryServer { get; set; }
public string DatabaseName { get; set; }
public int DomainId { get; set; }
public int CurrencyTypeId { get; set; }
public virtual Client Client { get; set; }
public virtual CurrencyType CurrencyType { get; set; }
public virtual Domain Domain { get; set; }
public virtual JobType JobType { get; set; }
public virtual Server DbServer { get; set; }
public virtual Server OpServer { get; set; }
public virtual Server OqServer { get; set; }
}
}
Possible ViewModel:
using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using TestIODSManagement.Models;
namespace TestIODSManagement.ViewModels
{
public class ClientJobsViewModel
{
private DeploymentsEntities db = new DeploymentsEntities();
public int Id { get; set; }
public int ClientId { get; set; }
public int JobTypeId { get; set; }
public string OlapAppName { get; set; }
public string EdgeAppName { get; set; }
public Nullable<int> DatabaseServer { get; set; }
public Nullable<int> ProcessingServer { get; set; }
public Nullable<int> QueryServer { get; set; }
public string DatabaseName { get; set; }
public int DomainId { get; set; }
public int CurrencyTypeId { get; set; }
public virtual Client Client { get; set; }
public virtual CurrencyType CurrencyType { get; set; }
public virtual Domain Domain { get; set; }
public virtual JobType JobType { get; set; }
public virtual Server DbServer { get; set; }
public virtual Server OpServer { get; set; }
public virtual Server OqServer { get; set; }
private List<Client> _clients;
public IList<Client> Clients { get { return _clients.AsReadOnly(); } }
private List<Domain> _domains;
public IList<Domain> Domains { get { return _domains.AsReadOnly(); } }
private List<CurrencyType> _currencyTypes;
public IList<CurrencyType> CurrencyTypes { get { return _currencyTypes.AsReadOnly(); } }
private List<JobType> _jobTypes;
public IList<JobType> JobTypes { get { return _jobTypes.AsReadOnly(); } }
private List<Server> _databaseServers;
public IList<Server> DatabaseServers { get { return _databaseServers.AsReadOnly(); } }
private List<Server> _processingServers;
public IList<Server> ProcessingServers { get { return _processingServers.AsReadOnly(); } }
private List<Server> _queryServers;
public IList<Server> QueryServers { get { return _queryServers.AsReadOnly(); } }
public ClientJobsViewModel(Client client)
{
ForceClientList(client);
SetSelectLists();
}
public ClientJobsViewModel(int jobId)
{
ClientJob job = db.ClientJobs.Find(jobId);
Client thisClient = db.Clients.Find(job.ClientId);
ForceClientList(thisClient);
SetSelectLists();
}
private void ForceClientList(Client client)
{
_clients = db.Clients
.Where(c => c.Id == client.Id)
.ToList();
}
private void SetSelectLists()
{
_databaseServers = db.Servers
.Where(s => s.ServerPurpos.PurposeName == "DataWarehouse").ToList();
_processingServers = db.Servers
.Where(s => s.ServerPurpos.PurposeName == "Processing").ToList();
_queryServers = db.Servers
.Where(s => s.ServerPurpos.PurposeName == "Querying").ToList();
_domains = db.Domains.ToList();
_currencyTypes = db.CurrencyTypes.ToList();
_jobTypes = db.JobTypes.ToList();
}
}
}

Answer 1

You're right that the controller is not the right place, but neither is the view model. Ideally, your view model should only contain properties to encapsulate the data, and rarely any functionality. I would place all that logic in a dedicated data layer, or failing that if it's small, simple project, a class dedicated to data access.
Then, the controller should be the one to call into that layer, class or service and request that the view model be populated.

Answer 2

There is difference between ViewModel and Model. ViewModel is only custom class - crate which pass data between view and controller in strongly typed fashion. Model is "something" your controller calls to get data, business logic, etc. It can be service layer, business logic class, repository or whatever else. Data access is part of Model.