Does it make sense to have Business Logic within a ViewModel in MVC?

Question

At the moment I'm working on Asp.Net MVC using: Repository, Unit-Of-Work patterns, Service Layer and ViewModels.

In this project every View is linked to a ViewModel Class, the Controllers are thin-one, so the Business Layer reside on a Service Layer.

I create instances of ViewModel class in the Controller and pass it to the view like this

    public ActionResult Create()
    {
        EventCreateViewModel eventViewModel = new EventCreateViewModel();
        return View(eventViewModel);
    }

In some ViewModel I use to call the Service Layer.

The system works, but I would like to know if it is a good idea adding call to a Service Layer in the ViewModel or better would be leave this operation only to the Controller.

 public class EventCreateViewModel
    {

        public CandidateListViewModel CandidateList = new CandidateListViewModel();

        public EventCreateViewModel()
        {
            DateTimeStart = DateTime.UtcNow;    // Add a default value when a Date is not selected
        }
    }
}

using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;

using System.Web.Mvc;
using System.ComponentModel.DataAnnotations;

    using System;
    using System.Collections.Generic;
    using System.Linq;
    using System.Web;

    using XXX.Models;
    using XXX.Service;

        namespace XXX.ViewModels
        {
            public class CandidateListViewModel
            {
                // We are using the Service Layer
                private ICandidateBL serviceCandidate;

                // Property
                public IDictionary<string, string> Candidates = new Dictionary<string, string>();

                // An utility method that convert a list of Canddates from Enumerable to SortedDictionary
                // and save the result to an inner SortedDictionary for store
                public void ConvertSave(IEnumerable<Candidate> candidates)
                {
                    Candidates.Add("None", "0");    // Add option for no candidate
                    foreach (var candidate in candidates)
                        Candidates.Add(candidate.Nominative, candidate.CandidateId.ToString());
                }

                #region Costructors
                public CandidateListViewModel()
                {
                    serviceCandidate = new CandidateBL();
                    ConvertSave(serviceCandidate.GetCandidates());
                }

                // Dependency Injection enabled constructors
                public CandidateListViewModel(ICandidateBL serviceCandidate)
                {
                    this.serviceCandidate = serviceCandidate;
                }

                public CandidateListViewModel(IEnumerable<Candidate> candidates)
                {
                    serviceCandidate = new CandidateBL();
                    ConvertSave(candidates);
                }
                #endregion
            }
        }

Dennis Traub Dennis Traub · Accepted Answer · 2012-10-08T06:10:18

The controller is the component that should be in control, so to say. The ViewModel should just be a data container, nothing more.

Remember the Single Responsibility Principle. Once you start distributing logic it will become increasingly difficult to remember and understand all the moving parts.

Does it make sense to have Business Logic within a ViewModel in MVC?

1 Answers