I'm developing a new MVC site for my company & kind of confused as how to create mapping from Domain/POCO objects to ViewModel classes [contains validation] & vice versa. Here's an sample example.
My domain class [just to keep it simple I'hv omitted other properties]:
public partial class Glossary
{
public int Id { get; set; }
public string GlossaryItem { get; set; }
public string Definition { get; set; }
}
my ViewModel class inside my MVC app's model folder [with corrosponding validation]:
public class GlossaryModel
{
[HiddenInput(DisplayValue = false)]
public int Id { get; set; }
[Required(ErrorMessage = "Please enter a GlossaryItem")]
public string GlossaryItem { get; set; }
[Required(ErrorMessage = "Please enter a Definition")]
public string Definition { get; set; }
}
my Automapper configuration for DTO to Domain Model:
protected override void Configure()
{
CreateMap<GlossaryModel, Glossary>();
//....... etc
}
My controller's action method for editing an item:
public class GlossaryController : Controller
{
IGlossaryRepository _glossaryRepository;
IMappingService _mappingService;
public GlossaryController(IGlossaryRepository glossaryRepository, IMappingService autoMapperMappingService)
{
_glossaryRepository = glossaryRepository;
_mappingService = autoMapperMappingService;
}
// .... etc
[HttpPost, ValidateAntiForgeryToken]
public virtual ActionResult Edit(GlossaryModel glossaryModel)
{
if (ModelState.IsValid)
{
var glossary = _mappingService.Map<GlossaryModel, Glossary>(glossaryModel);
if (glossaryModel.Id <= 0)
_glossaryRepository.Add(glossary);
else
_glossaryRepository.Edit(glossary);
_glossaryRepository.Save();
TempData["message"] = string.Format("{0} has been saved", glossaryModel.Definition);
return RedirectToAction("All");
}
return View(glossaryModel);
}
//....etc
}
And it's working fine, but my question is... Now say I need an action that will list down all glossary items like..
public ActionResult All()
{
var allItems = _glossaryRepository.Glossary;
if (allItems.Count() == 0) return View(new List<GlossaryModel>());
// **The below line is the reverse mapping one**
var allItemsModel = _mappingService.Map<IEnumerable<Glossary>, IEnumerable<GlossaryModel>>(allItems);
return View(allItemsModel);
}
But now I need automapper to convert from Domain objects to DTO [from List(Glossary) to List(GlossaryModel)], just opposite of the Edit method, to push the data to the view. So do I again need to map the opposite binding in the automapper config...!! like
protected override void Configure()
{
CreateMap<GlossaryModel, Glossary>(); // Added before for DTO to Domain object
CreateMap<Glossary, GlossaryModel>();// Added for Domain object to DTO
//....... etc
}
Is it a good design to bind both ways? or there's better solution I'm missing, Please help
Thanks,
Sanjay
Jimmy Bogard also asked the same question. But there was enough demand for it that direct support has been added for simple cases like you've listed. In fact, in this answer Jimmy also suggested that there's nothing wrong with it if it works for you. A simple example is:
protected override void Configure()
{
CreateMap<GlossaryModel, Glossary>()
.ReverseMap();
//....... etc
}
Note that ReverseMap doesn't work for more complex mappings. See this answer for more details.
Automapper was build to Domain to ViewModel (Domain to DTO in the manner in which you've described it) mapping
Summed up well by #Marius' answer here What is wrong with two-way mapping?
In some medium sized projects I've used two way mapping and for larger projects I use Domain To View Model mapping and then used a CQRS system for sending the ViewModel values to the underlying persistence store.
When it comes down to it, it is up to you how you choose to use Automapper and what Architectural decisions make sense to you.
The world will not stop rotating if you do 2 way mapping.
Related
I am trying to understand and implement different UI patterns in .NET to see the pros and cons and where they suite best.
I understand the main concept but I was creating an app and a question appeared.
Say we have a class Customer, which represents the core Information of a customer.
public class Customer
{
public int Id { get; set; }
public string Name { get; set; }
public string Address { get; set; }
public string City { get; set; }
public string Country { get; set; }
public string PostalCode { get; set; }
public string PhoneNumber { get; set; }
}
Now, if I create a WebView or WebForm to show all customers I can use this class to set as source f.e. to a DGV, being able to show all properties above.
But then I want to show for example a View/Form with the Revenue history of each customer.
So there is a class CustomerRevenue like
public class CustomerRevenue
{
public Revenue ActualYearExpectedRevenue { get; set; }
public IList<Revenue> RevenuePerYearList { get; set; }
public decimal ActualYearProjectedRevenue => CalculateYearProyection();
public decimal CalculateYearProyection(int year)
{
var daysInYear = DateTime.IsLeapYear(year) ? 365 : 366;
var actualYearRevenue = RevenuePerYearList.SingleOrDefault(x => x.Year == year);
var dayNumber = DateTime.Now.DayOfYear;
var projection = ((actualYearRevenue.Amount * daysInYear) / dayNumber);
return projection;
}
}
Here, to set RevenuePerYearList we need some time, since let's say we sell a lot and have a huge list of sells with huge lists of articles, so the calculation needs some time.
So now my question:
Should I then have "concrete" classes for each view/model with the data I want to show, i.e. here I would have apart of Customer class, say a CustomerRevenueModel
public class CustomerRevenueModel
{
private readonly CustomerRevenue _customerRevenue = new CustomerRevenue();
public int Id { get; set; }
public string Name { get; set; }
public string Address { get; set; }
public string City { get; set; }
public string Country { get; set; }
public string PostalCode { get; set; }
public CustomerRevenue CustomerRevenue
{
get { return _customerRevenue; }
}
}
}
which has (maybe) different properties, so I need to load this "heavy" properties when needed
or
should I stay with only one class (I mean, a customer always has a revenue) and leave the properties "empty"?
The first option makes me have a lot of classes, one for each view/form I want to show data for (maybe being able to reuse some models in various views/forms) but keeps all clean and in a valid state. And also each class can have it's own logic (domain logic - DDD)
The second option is less classes, less code, but some way I end having a huge (God) class, with all the properties a Customer has and all it's logic (methods). I load only the ones I need, but this appears really bad to me.
The third option is to have the big class with all properties and methods as my (domain)model, and create a "ViewModel" (which contains no methods, only props) each time I need to show sth. like above , using it as source for my GridView. This is the solution with more classes and code (big class + ViewModels + (maybe) DTOs), but also the more organized and SOLID design to my eyes... Here the use of a Mapper like AutoMapper would really help, mapping between objects
But this is the part I'm confused about...
Are these "ViewModels" a bad pattern using MVC or MVP?
Are this the same as the VM in MVVM? Which I Think not, since I've understood VM in MVVM like a "template", but what I talk about appears to me more like DAOs??
Or they don't have nothing to do, are just DAOs
I think I am a bit confused about all the different meanings of Model, ViewModel etc, in the different design patterns.
I am hardly trying to understand right MVC,MVP,MVVM and DDD and I think sometimes I am mixing terms...?
First, try to not "mix" things from different patterns, ViewModels are for MVVM, and you NEED ViewModels if you want to implement MVVM (ASP.Net MVC uses something called ViewModels, but it is not the same than the ViewModels in MVVM design pattern)
The ViewModel is like a model for the View. The ViewModel work is to "convert" the Model(s) to something the View can understand.
You can have one o more models (or none) and use it in the ViewModel, you have a ViewModel for each View.
In your example (a datagridview) you can have a model that will represent the data in a datagridview, a DTO if you want, and you can have a property in the ViewModel, a List and you will fill with data loaded from the database. In the View, you will bind that property (the list) to the dgv datasource.
Think that the ViewModel is something like the code behind of the view, but you are working with properties and commands that will be binded to controla in the view.
I've been googling like crazy without result, maybe I'm just missing the correct keywords.
I have a class with a custom validation attribute on a property. I want to "clean" the value before validation, removing the white-space and special characters that we accept but that we don't want to save to the database.
public class PersonViewModel
{
[SocialSecurityNumberLuhn(ErrorMessage = "Incorrect social security number")]
public string SocialSecurityNumber { get; set; }
}
I would want to do something like this:
public class PersonViewModel
{
[CleanWhiteSpace]
[SocialSecurityNumberLuhn(ErrorMessage = "Incorrect social security number")]
public string SocialSecurityNumber { get; set; }
}
For example 1985-03-15-1234 should be saved and validated as 19850315-1234.
Any suggestions? What's the neatest approach?
If you change the auto-implemented property into a manual-implemented property then you can perform the "cleaning" step when the value is set, so it can only be stored in the model in a "clean" state. Something like this:
public class PersonViewModel
{
private string _socialSecurityNumber;
[SocialSecurityNumberLuhn(ErrorMessage = "Incorrect social security number")]
public string SocialSecurityNumber
{
get { return _socialSecurityNumber; }
set
{
_socialSecurityNumber = CleanSocialSecurityNumber(value);
}
}
}
The recommended approach here is to use a service layer. View models should not include any logic. With a service layer Your controller would call a method on its associated service and this method would return your view model with the clean SSN.
In this tutorial you will see how the service layer can be structured and you could adapt the pattern to clean your data before validation.
http://www.asp.net/mvc/tutorials/older-versions/models-(data)/validating-with-a-service-layer-cs
The use of a ValidationAttribute in your example would be an incorrect usage also.
Controller where you would inject / instantiate the service class
public ActionResult GetPerson(int PersonId){
return _personService.GetPerson(personId);
}
The service method
public PersonViewModel GetPerson(int Id){
// get the data (maybe from DAL) and clean returning view model
return new PersonViewModel(){SocialSecurityNumber = Clean(...)};
}
Hope this gives you some direction.
I have an ASP.Net MVC 5 (C#) application and I'm giving my users the ability to like posts and comments.
for this I have a Model called Likes with the following Properties:
public class Like
{
public Like()
{
this.CreatedUTC = System.DateTime.UtcNow;
this.isActive = true;
}
public long id { get; set; }
public string UserID { get; set; }
public bool isActive { get; set; }
public LikeType Type { get; set; }
public DateTime CreatedUTC { get; set; }
}
Type is an enum and it can be either Comments or Posts. I've also added the following Navigation Property to both Post Model and Comment Model:
public virtual ICollection<Like> Likes { get; set; }
My question is, can I have a setter function in the above line of code where it would automatically set Comments and Posts for the Like type? I know I can use the Value variable in the Setter but using Google I couldn't find how to use it for complex types as I have above (Like).
I'm sure this would be a better way of doing this than in the repository manually set that enum every-time I'm going to save a like.
UPDATE:
Seeing how we're starting a nice little conversation about this Questions, I will throw another alternative in the mix.
How about two Tables with a base class of Like, one CommentLikes and the other PostLikes Seeing that the size of this table will grow really fast, I'm thinking separating them would possibly be a good thing, Right?
I'd rather drop the "LikeType" and either have Comment and Post entity in the Like entity and distinguish by one of them being null or introduce two new entities
public class CommentLike
{
public Comment Comment { get; set; }
public Like Like { get; set; }
}
which holds a comment and a like and PostLike which holds a Post and a Like. The Comment then looks like this
public Comment
{
public virtual ICollection<CommentLike> { get; set; }
}
Another alternative is to create separate tables for comment and post likes. While what you ask for is definitely doable I would recommend more verbose but simpler solution which will result in code that is easier to maintain and has less bugs. Is there any specific reason you want to have a LikeType property?
I had same problem but didnt encounter an easy way.
class Post{
public virtual ICollection<Like> Likes {set;get;}
}
class Comment{
public virtual ICollection<Like> Likes {set;get;}
}
Then:
class Like{
//....
}
You dont need a bi-directional relationship. Do you have a case where you need to query Likes table? and if you do, you will have to manage parsing it as ENUM somewhere which can be an extension method.
EF will create Post_Id and Comment_Id implicityly in your table design. You wont be able to query it but you wont need to. IN my experience i never needed to.
My question is, can I have a setter function in the above line of code
where it would automatically set Comments and Posts for the Like type?
I assume you are using T4 template or the classes that were generated by EF are partialthen you can extend it by creating another partial class and a wrapper property for Likes
// Backing field
private ICollection<Like> _likesWrapper;
public ICollection<Like> LikesWrapper {
get {
// Lazy loading
if(_likes == null)
{
// Just create a new list or load it from the database.
_likes = new List<Like>();
}
return _likes;
}
set {
foreach(var val in value)
{
//Set the comment and posts
}
Likes = value;
}
I am trying to separate/refactor code into folders and move all my 'Fill' properties into a logical place.
Is there a technical name for populating properties using a function
example:
public class AccountsView
{
public string Email { get; set; }
public string FirstName { get; set; }
public string LastName { get; set; }
}
This would be place in its own Class .. right now its within the above class
public static AccountsView FillCustomerView(Account data)
{
view.Email = data.Email;
view.FirstName = data.FirstName;
view.LastName = data.LastName;
return view;
}
What would this 'FillCustomerView()' function be called?
The concept described here is called object mapping, and in this example it is implemented as a method on view model.
The drawback of this implementation is that it couples the view models to domain models, and this is usually frowned upon. To avoid this, mapper objects are typically used - they define projection from one model to another.
You could use some already existing implementation. Most popular seems to be Automapper, but there are others. E.g. the excellent ServiceStack framework also supports it.
I'm trying to learn MVC by building a full-featured website. I'm a little stuck when it comes to dealing with forms, and posting data, and models....
BTW: I'm using EF Code-First w/MS SQL CE
Here's the Models in question:
public class Assignment
{
public int AssignmentID { get; set; }
public int? CourseID { get; set; }
public string Name { get; set; }
// etc...
public virtual Course Course { get; set; }
}
public class Course
{
public int CourseID { get; set; }
// etc...
}
I'm loading a partial view that allows the user to add a new assignment
Controller:
public ActionResult Assignments()
{
var assignments = myContext.Assignments.OrderBy(x => x.DueDate);
return View(assignments);
}
[HttpPost]
public ActionResult AddAssignment(Assignment assignment)
{
myContext.Assignments.Add(assignment);
myContext.SaveChanges();
return RedirectToAction("Assignments");
}
// Returns a strongly-typed, partial view (type is Assignment)
public ActionResult AddAssignmentForm()
{
return PartialView();
}
Here's where I'm stuck: I want this form to have a drop down list for the different courses that an assignment could possibly belong to. For example, an assignment called "Chapter 3 Review, Questions 1-77" could belong to course "Pre-Algebra". However, if I use the code below, I have to explicitly declare the SelectListItems. I thought that with the given Assignment model above, I should be able to have the drop down list for Courses automatically generated using MVC awesomeness. What am I doing wrong?
AddAssignment Partial View:
#model MyModels.Assignment
#using(Html.BeginForm("AddAssignment", "Assignments"))
{
// Can't I create a drop down list without explicitly
// setting all of the SelectListItems?
#Html.DropDownListFor(x => x.Course, ....
}
Basically you are confusing/mixing your business model and your UI model.
The quick fix here is to add the data for the dropdown list to the ViewBag (a dynamic object).
Alternatively you could create a class AssignmentModel that contains the relevant Assignment properties and the List.
And No, this is not well supported in the templates.
You do realize you'll need some error handling in the Post method(s)?