I have an MVC application. The following code is being used in multiple places within a controller and in multiple controllers. I would like to have this code in one place and call it from each location. What's the best way to do that in MVC?
The code below gets a row from the database and creates ViewData that can be read from the view. With webforms, I would create a public sub within a class and pass the year and month values. Is there a way this code could become part of the model?
var monthlyexpenseincome = (from vu_monthlyresult in dbBudget.vu_MonthlyResults
where vu_monthlyresult.Month == defaultmonth && vu_monthlyresult.Year == defaultyear
select vu_monthlyresult).Single();
var yearlyexpenseincome = (from vu_yearlyresult in dbBudget.vu_YearlyResults
where vu_yearlyresult.Year == defaultyear
select vu_yearlyresult).Single();
ViewData["MonthlyExpenses"] = monthlyexpenseincome.Expenses;
ViewData["MonthlyIncome"] = monthlyexpenseincome.Income;
ViewData["MonthlyProfit"] = monthlyexpenseincome.Income - monthlyexpenseincome.Expenses;
Generally, If you have common code across multiple controllers, you can create another class which inherits from Controller and keep your methods there and let your indidual Controlellers inherit this new class
public class BaseController : Controller
{
protected string GetThatInfo()
{
//do your magic logic and return some thing useful
return "This is demo return.Will be replaced";
}
}
And now you can inherit from this for your other controllers
public class UserController: BaseController
{
public ActionResult Index()
{
return VieW();
}
}
But In your case, The data you are taking is something specific to your Domain data. so i would suggest you to move it to a different class ( like a new Service / Business Layer)
public static class ProfitAnalysis
{
public static decimal GetTotalExpense()
{
//do your code and return total
}
}
And you can call it from wherever you wanted like
decimal totalExp=ProfitAnalysis.GetTotalExpense();
And You will soon realize, Having so much ViewData usage is making your code difficult to read and Maintain. Do not wait for that day. Switch to strongly typed classes to pass data.
You should place your queries in a "business layer", which is just a class that you call to do the business logic. Then you can reuse it in any place you like, just instantiate the business class and use it. You could also make the methods static if they don't require state, then you wouldn't have to even instantiate it.
For example:
var expenseService = new expenseService();
ViewData["MonthlyExpenses"] = expenseService.GetMonthlyExpenses();
Related
In one of my Controllers Action Method I get the current week number and it's passed to the View. I realize that I could need the week number in other Controllers and Views, but I don't want to copy/paste the same code at different places in my project.
I'm looking for a simple and smart solution where I can reuse the code from just one place like a static class or a global object or something similar. If it was within the same Controller I could have done a method to call, but since I need it from other Controllers, I need another solution and I'm not sure how to achieve this? Any suggestions?
You can create a class that inherits from Controller.
I create a BaseController class like so:
public class BaseController : Controller
{
protected someDBContext db = new someDBContext();
protected User currentUser;
public static ILog ErrorLogger = LogManager.GetLogger("ErrorLogger");
protected override void Initialize(RequestContext requestContext)
{
base.Initialize(requestContext);
if (Session["UserID"] != null)
{
currentUser = UserToStaff.GetCurrentUser(
(int)Session["userId"],
db
);
}
ViewBag.currentUser = currentUser;
addNoticesToViewBag();
}..
I add functions and properties for common tasks like
creating the dbContext, creating the currentUser object, and setting up logging in here.
Don't let it grow arms and legs though.. the Initialize is going to fire with every request.
I have read that in an MVC application one should keep controllers "thin". But when I put code to fetch data in the ViewModel I feel it's less intuitive to locate, meaning when I am troubleshooting I generally tend to look in my controller first (or maybe that's my real problem). Also I find one can reuse the same VM for many different things if you pass data through the controller.
Am I violating some big principle or causing performance issues?
For example, compare these dummy snippets with two approaches, both seem to work just fine:
Assume a Repository called repositoryy with a method GetCourses() that fetches a list of Courses.
1) ViewModel fetches the data and controller directs traffic:
public CourseViewModel
{
private MyProjectEntities db = new MyProjectEntities();
Repository repository = new Repository();
{
public CourseViewModel()
{
Courses = db.Course.ToList();
}
public List<Course> Courses {get; set;}
}
}
public class CourseController : Controller
{
public ActionResult Index()
{
var courseviewmodel = new CourseViewModel();
return View(courseviewmodel);
}
}
2) Controller fetches data, passes to ViewModel and then to the View:
public CourseViewModel
{
public List<Course> Courses {get; set;}
}
public class CourseController : Controller
{
public ActionResult Index()
{
var courseviewmodel = new CourseViewModel();
courseviewmodel.Courses = repository.GetCourses.ToList();
return View(courseviewmodel);
}
}
The second option. Btw there's no 'more correct MVc approach'. There is the MVC separation and that's that. Your first option breaks that separation, because the view model does the controller's work instead of being the 'dumb' dto holding the view's data. You don't want to couple the view model to the model.
In MVVM though, the view model acts a bit like a controller, however that approach is best suited for desktop aps, not web apps.
I'm a bit confused if saving the information to session code below, belongs in the controller action as shown below or should it be part of my Model?
I would add that I have other controller methods that will read this session value later.
public ActionResult AddFriend(FriendsContext viewModel)
{
if (!ModelState.IsValid)
{
return View(viewModel);
}
// Start - Confused if the code block below belongs in Controller?
Friend friend = new Friend();
friend.FirstName = viewModel.FirstName;
friend.LastName = viewModel.LastName;
friend.Email = viewModel.UserEmail;
httpContext.Session["latest-friend"] = friend;
// End Confusion
return RedirectToAction("Home");
}
I thought about adding a static utility class in my Model which does something like below, but it just seems stupid to add 2 lines of code in another file.
public static void SaveLatestFriend(Friend friend, HttpContextBase httpContext)
{
httpContext.Session["latest-friend"] = friend;
}
public static Friend GetLatestFriend(HttpContextBase httpContext)
{
return httpContext.Session["latest-friend"] as Friend;
}
I wouldn't worry too much about where you put your code to save the model to session. It's one line of code so you are not saving anything or making anything clearer by extracting it out.
For creating your Friend object, I personally would either use something like Automapper, or have a populate method on my view model.
var friend = viewModel.Populate(new Friend());
public void Populate(Friend friend)
{
friend.FirstName = this.FirstName;
}
As for saving the friend to session, if you do want to extract it, I would do something similar to your static methods but as session extension methods. Just because it makes it immediately clear where it's being stored.
// set
Session.LatestFriend(friend);
// get
var latestFriend = Session.LatestFriend();
Controller is the right place to store and get data, and populate models with that Data.
Models are used as support for that data to be shown within views.
So what you're doing is pretty correct.
No need for the static class that will just get or store from Session, as it is about only one line of code.
+1 for the advice of Bigfellahull when dealing with multiple fields initialization.
I've been trying to find a good way to handle the Models of our Asp.net MVC websites when having common properties for all the pages. These properties are to be displayed in the Layout (Master Page). I'm using a "BaseModel" class that holds those properties and my Layout use this BaseModel as its model.
Every other model inherits from that BaseModel and each has specific properties relative to the view it represents. As you might have guessed, my Models are actually View Models even if that's not quite relevant here.
I have tried different ways to initialize the BaseModel values
By "hand" in every view
Having a base controller that has an Initialize virtual method to do it (so specific controller can implement specific common behavior for exemple)
Having a base controlelr that override OnActionExecuting to call the Initialize method
Using a helper class to do it outside of the controller
Using a Model Factory
But none of those really appeal to me:
Seems obvious to me, but DRY is one reason enough to justify that (actually I never tried that solution at all, I'm just putting it to be able to loop on that point in the last point).
I don't like that one because it means that whenever a new Controller is added, you need to know that it has to inherit from the BaseController and that you need to call the Initialize method, not to mention that if your controller has overriden the base one, to call the base anyway to maintain the values.
see next point
and 3. are a variation on the same topic but that doesn't really help with the issues of the second solution.
My favorite so far, but now I have to pass a few more variables to set those values. I like it for the inversion of dependence. But then if I want to provide values from the session, I need to pass them explicitly for exemple, then I'm back to square one as I have to provide them by hand (being references or through an interface of any kind)
Of course, (almost) all of those solutions work, but I'm looking for a better way to do it.
While typing this question, I found maybe a new path, the builder pattern that might also do, but implementations can become quickly a burden too, as we can have dozens of views and controllers.
I'll gladly take any serious recommandation/hint/advice/patterns/suggestion !
Update
Thanks to #EBarr I came up with another solution, using an ActionFilterAttribute (not production code, did it in 5 minutes):
public class ModelAttribute : ActionFilterAttribute
{
public Type ModelType { get; private set; }
public ModelAttribute(string typeName) : this(Type.GetType(typeName)) { }
public ModelAttribute(Type modelType)
{
if(modelType == null) { throw new ArgumentNullException("modelType"); }
ModelType = modelType;
if (!typeof(BaseModel).IsAssignableFrom(ModelType))
{
throw new ArgumentException("model type should inherit BaseModel");
}
}
public override void OnActionExecuting(ActionExecutingContext filterContext)
{
var model = ModelFactory.GetModel(ModelType);
var foo = filterContext.RequestContext.HttpContext.Session["foo"] as Foo;
model.Foo = foo;
model.Bar = somevalue;
filterContext.Controller.TempData["model"] = model;
}
}
Calling it is then really simple:
[Model(typeof(HomeModel))]
public ActionResult Index()
{
var homeModel = TempData["model"] as HomeModel;
// Add View Specific stuff
return View(homeModel);
}
And it gives me the best of every world. The only drawback is to find a proper way to passe the model back to the action.
Here it's done using the TempData object, but I also consider updating the model that one can find in the ActionParameters.
I'm still taking any serious recommandation/hint/advice/patterns/suggestion for that, or the previous points.
I went through almost exactly the same process as I dove into MVC. And you're right, none of the solutions feel that great.
In the end I used a series of base models. For various reasons I had a few different types of base models, but the logic should apply to a single base type. The majority of my view models then inherited from one of the bases. Then, depending on need/timing i fill the base portion of the model in ActionExecuting or OnActionExecuted.
A snippet of my code that should make the process clear:
if (filterContext.ActionParameters.ContainsKey("model")) {
var tempModel = (System.Object)filterContext.ActionParameters["model"];
if (typeof(BaseModel_SuperLight).IsAssignableFrom(tempModel.GetType())) {
//do stuff required by light weight model
}
if (typeof(BaseModel_RegularWeight).IsAssignableFrom(tempModel.GetType())) {
//do more costly stuff for regular weight model here
}
}
In the end my pattern didn't feel too satisfying. It was, however, practical, flexible and easy to implement varying levels of inheritance. I was also able to inject pre or post controller execution, which mattered a lot in my case. Hope this helps.
The idea that gave me #EBarr to use an action filter was actually working but felt wrong in the end, because there was no clean way to retrieve the model without passing through a viewbag, or the httpcontext items, or something alike. Also, it made mandatory to decorate every action with its model. It also made the postback more difficult to handle. I still believe that this solution has merits and might be useful in some specific scenarios.
So I was back to square one and started looking more into that topic. I came to the following. First the problem has two aspects
Initializing the data for the views
Rendering the data
While looking for more idea, I realized that I was not looking at the problem from the right perspective. I was looking at it from a "Controller" POV, whereas the final client for the model is the view. I was also reminded that the Layout/Master page is not a view and should not have a model associated with it. That insight put me on what feels the right path for me. Because it meant that every "dynamic" part of the Layout should be handled outside of it. Of course, sections seems the perfect fit for that, because of their flexibility.
On the test solution I made, I had (only) 4 different sections, some mandatory, some not. The problem with sections, is that you need to add them on every page, which can quickly be a pain to update/modify. To solve that, I tried this:
public interface IViewModel
{
KeyValuePair<string, PartialViewData>[] Sections { get; }
}
public class PartialViewData
{
public string PartialViewName { get; set; }
public object PartialViewModel { get; set; }
public ViewDataDictionary ViewData { get; set; }
}
For exemple, my model for the view is this:
public class HomeViewModel : IViewModel
{
public Article[] Articles { get; set; } // Article is just a dummy class
public string QuickContactMessage { get; set; } // just here to try things
public HomeViewModel() { Articles = new Article[0]; }
private Dictionary<string, PartialViewData> _Sections = new Dictionary<string, PartialViewData>();
public KeyValuePair<string, PartialViewData>[] Sections
{
get { return _Sections.ToArray(); }
set { _Sections = value.ToDictionary(item => item.Key, item => item.Value); }
}
}
This get initialized in the action:
public ActionResult Index()
{
var hvm = ModelFactory.Get<HomeViewModel>(); // Does not much, basicaly a new HomeViewModel();
hvm.Sections = LayoutHelper.GetCommonSections().ToArray(); // more on this just after
hvm.Articles = ArticlesProvider.GetArticles(); // ArticlesProvider could support DI
return View(hvm);
}
LayoutHelper is a property on the controller (which could be DI'ed if needed):
public class DefaultLayoutHelper
{
private Controller Controller;
public DefaultLayoutHelper(Controller controller) { Controller = controller; }
public Dictionary<string, PartialViewData> GetCommonSections(QuickContactModel quickContactModel = null)
{
var sections = new Dictionary<string, PartialViewData>();
// those calls were made in methods in the solution, I removed it to reduce the length of the answer
sections.Add("header",
Controller.UserLoggedIn() // simple extension that check if there is a user logged in
? new PartialViewData { PartialViewName = "HeaderLoggedIn", PartialViewModel = new HeaderLoggedInViewModel { Username = "Bishop" } }
: new PartialViewData { PartialViewName = "HeaderNotLoggedIn", PartialViewModel = new HeaderLoggedOutViewModel() });
sections.Add("quotes", new PartialViewData { PartialViewName = "Quotes" });
sections.Add("quickcontact", new PartialViewData { PartialViewName = "QuickContactForm", PartialViewModel = model ?? new QuickContactModel() });
return sections;
}
}
And in the views (.cshtml):
#section quotes { #{ Html.RenderPartial(Model.Sections.FirstOrDefault(s => s.Key == "quotes").Value); } }
#section login { #{ Html.RenderPartial(Model.Sections.FirstOrDefault(s => s.Key == "header").Value); } }
#section footer { #{ Html.RenderPartial(Model.Sections.FirstOrDefault(s => s.Key == "footer").Value); } }
The actual solution has more code, I tried to simplify to just get the idea here. It's still a bit raw and need polishing/error handling, but with that I can define in my action, what the sections will be, what model they will use and so on. It can be easily tested and setting up DI should not be an issue.
I still have to duplicate the #section lines in every view, which seems a bit painful (especialy because we can't put the sections in a partial view).
I'm looking into the templated razor delegates to see if that could not replace the sections.
In a heavy enviroment application, we have Users, Locations, bla bla bla... and we use in many situations a call to a service where we retrieve the list of countries.
Where is the 'best practice' or 'proper way' to implement this. This method is called in several places and many objects has a List<CountryVO> property.
Specially considering using Razor views an often having to add this property to ModelViews
The solution is using DAL / BLL / SERVICE / UI[s] architecture.
Real Example:
public class User {
...
...
public List<DeliveryZoneVO> DeliveryZones {get;set;}
public User() {
...
DeliveryZones = service.GetDeliveryZones().ToList();
}
}
The class DeliveryZoneVO comes from a webservice, so one property is
int IdCountry
The class User have a list of DeliveryZoneVO as presented on the class, the 'problem' here, is since it retrieves the data from a web service, I only have the ID of the country.
When I prepare the data in the controller to send to the View:
UserModelView userMV = new UserModelView();
userMV.user = service.GetUserById(1);
ViewData.Model = userMV;
BUT, inside userMV.user, I have DeliveryZones with a list of DeliveryZoneVO objects with IdCountries.
In the view, when I do (for example) :
#DisplayFor(m => m.user.DeliveryZones)
I want to show the Country Name, only have the ID. So i need a reference somewhere.. the question lies in where should that data needs to be placed that is considered BEST PRACTICES.
Is having in all modelview (in the case of the example, the UserModelView() the property Countries with a List ?
A good thing because this kind of issues is to have a BaseController class that derived from controller, and all the other controllers you have derived from it.
in the BaseController put a static List<CountryVO> property with getter only, this way it will be initialized once and will be accessible to all of your's controllers and views(If you pass it with the ViewModel or ViewBag).
Example:
public class BaseController : Controller
{
private static List<CountryVO> _allCountries;
public static List<CountryVO> AllCountries
{
get{ return _allCountries ?? _GetCountriesFromSomeWhere();}
}
}
public class HomeController : BaseController
{
public ActionResult Index()
{
ViewBag.AllCountries = this.AllCountries;
return View();
}
}
I would create a partial view that is responsible for just rendering the country list. Then any changes to how the list is rendered is can be made in just one place. I would create a model class that encapsulates calling the service to get the countries. Assuming that the country list is fairly static you could handle caching of the information in the model class for less calls to the service and better performance. Below is an example of a method in the model that gets the country list from the server cache if it is available.
const string cacheId = "deliveryZones";
public List<DeliveryZoneVO> GetDeliveryZones()
{
List<DeliveryZoneVO> deliveryZones = (List<DeliveryZoneVO>)HttpRuntime.Cache.Get(cacheId);
if (deliveryZones == null)
{
deliveryZones = service.GetDeliveryZones().ToList();
System.Web.HttpContext.Current.Cache.Insert(cacheId, deliveryZones);
}
return deliveryZones;
}