I've just started using AutoMapper in an MVC ASP.NET project to map my domain models to my view models. eg.
public class PersonModel
{
public string FirstName { get; set; }
public string NickName { get; set; }
public string LastName { get; set; }
public DateTime BirthDate { get; set; }
}
public class PersonViewModel
{
public string FirstName { get; set; }
public string NickName { get; set; }
public string LastName { get; set; }
public DateTime BirthDate { get; set; }
}
// Somewhere...
Mapper.CreateMap<PersonModel, PersonViewModel>();
Mapper.CreateMap<PersonViewModel, PersonModel>();
Having adopted this pattern, I'm concerned the following scenario happening in future:
1) Developer A creates Person View which shows editors for all 4x properties
2) Developer B later removes "Nickname" editor from the Person View, but leaves in PersonViewModel
3) Because the Nickname value is never preserved in the View, hence submitted on Save, Automapper starts mapping a null value for "Nickname" from PersonViewModel -> PersonModel and overwriting data without any run-time or compile-time warning.
Is this a legitimate risk, have you run into it, and how did you deal with it?
You can mitigate against such risks by having server side validation and automated end to end testing.
So in your example one of the tests would be that 'when saving a person the nickname should contain a value'.
Related
I had the idea to use Data Annotations in order to validate ModelState. This works wonderfully. The problem I am having is that the [Required] Data Annotation is being enforced on [Key] fields on post. Our data layer takes care of setting Id's and we don't want anyone consuming the service to have to worry about Id's. Is there a way around this in WebApi2?
I have looked at this question, and removing the Id field from ModelState in the POST method before checking for valid ModelState would work. The issue with that is that we use a filter for ModelState.
EDIT:
After doing some more research, what I am essentially wanting to do is what the [Bind] attribute does in MVC. After some research, it does not look like this is a feature that has yet been implemented in WebApi. If anyone has any ideas, feel free to post them.
What you can do is to replace your entity with a data transfer object, which is identical to your original entity without the ID field. For example,
The original entity may look like this
public class User
{
[Required]
public Guid UserId { get; set; }
public string Firstname { get; set; }
public string Lastname { get; set; }
public string Username { get; set; }
public string Email { get; set; }
}
and the DTO may look like this
public class UserDto
{
public string Firstname { get; set; }
public string Lastname { get; set; }
public string Username { get; set; }
public string Email { get; set; }
}
Hope this helps.
I have added computed fields(Active and CreditsLeft) directly into my CodeFirst entity class. Is it good idea to add computed field logic inside CF Entity class?
public class User : Entity
{
public User()
{
Id = Helper.GetRandomInt(9);
DateStamp = DateTime.UtcNow;
TimeZone = TimeZoneInfo.Utc.Id;
}
[DatabaseGenerated(DatabaseGeneratedOption.None)]
public int Id { get; set; }
[Required]
[MaxLength(50)]
public string Email { get; set; }
[Required]
[MaxLength(50)]
public string Password { get; set; }
[MaxLength(50)]
public string FirstName { get; set; }
[MaxLength(50)]
public string LastName { get; set; }
[Required]
public DateTime DateStamp { get; set; }
public virtual ICollection<Order> Orders { get; set; }
public virtual ICollection<Statistic> Statistics { get; set; }
public virtual ICollection<Notification> Notifications { get; set; }
[DatabaseGenerated(DatabaseGeneratedOption.Computed)]
public bool Active
{
get
{
return Orders.Any(c => c.Active && (c.TransactionType == TransactionType.Order || c.TransactionType == TransactionType.Subscription));
}
}
[DatabaseGenerated(DatabaseGeneratedOption.Computed)]
public int CreditsLeft
{
get
{
return Orders.Sum(p => p.Credits != null ? p.Credits.Value : 0);
}
}
}
Is it good idea to add computed field logic inside CF Entity class?
Sure, you can do this, but there are a few things you must take care of.
First, the attribute for a property that is computed by business logic is not [DatabaseGenerated(DatabaseGeneratedOption.Computed)], because this indicates that the value is computed in the database (as in a computed column). You should mark the property by the [NotMapped] attribute. This tells Entity Framework to ignore the property in database mapping.
Second, since both properties use Orders, you must make sure that the orders are loaded or can be lazy loaded when either property is accessed. So you may want to load Users with an Include statement (Include(user => user.Orders)). Or else you must ensure that the context is still alive when Active or CreditsLeft is accessed.
Third, you can't address the properties directly in an EF LINQ query, as in
db.Users.Select(u => u.Active);
because EF will throw an exception that it doesn't know Active. You can address the properties only on materialized user objects in memory.
Not sure how to explain this, but here goes...
I've built a code first data model using EF 4.3. One of classes, "Address" contains typical address data, street, city, state, etc. Other classes in the model contain instances of the "Address" class.
The problem. The data will be gathered/presented using different views, some of which will require the address fields, others that will not.
I can build different view models, each having the necessary validation attributes, and copy the data back and forth between data model and view model but that seems wrong.
What am I missing? There has to be a smarter way to do this.
Thanks for your help,
Jimmy
First read these questions and their answers:
MVC: Data Models and View Models
Why Two Classes, View Model and Domain Model?
also this article could help:
ASP.NET MVC View Model Patterns
In conclusion, I think in most scenarios it's helpful to have a chubby domain model (DM) but light weight presentation models (PM) related to it. So when we want to edit only a small chunk of that fat DM, one of our PMs will raise its hand.
Imagine this class in DM:
namespace DomainModels
{
public class Person
{
public int ID { get; set; }
public string FirstName { get; set; }
public string MiddleName { get; set; }
public string LastName { get; set; }
public DateTime? DoB { get; set; }
public MyAddressDM Address { get; set; }
public string Phone { get; set; }
public IEnumerable<MyCarModel> Cars { get; set; }
//etc.
}
}
Now imagine that in one view we need to edit only Address and Phone. A light weight PM could be like:
namesapce PresentationModels
{
public PersonAddressPhone
{
public int ID { get; set;}
public string FullName { get; set;}
public string AddressSteet { get; set; }
public string AddressCity { get; set; }
public string AddressState { get; set; }
public string AddressZipCode { get; set; }
public string Phone { get; set; }
}
}
and in another view we need to add/remove cars for a person:
namesapce PresentationModels
{
public PersonCars
{
public int ID { get; set;}
public string FullName { get; set;}
public IEnumerable<PMCar> Cars { get; set;}
}
}
Mapping between DO and PM is the golden piece of this puzzle. Be sure to take a look at AutoMapper.
Sorry about the title; couldn't think of a better one.
Any way, I'm accessing an associated property in my view like so:
#Model.Company.CompanyName // No problems here...
The model is a viewmodel mapped to an EF POCO. The Model has several properties associated to the Company table. Only one of the properties in the model share the same name as the PK in the Company table. All the other properties reference the same table:
public class MyModelClass
{
public int Id { get; set; }
public int CompanyId { get; set; }
public int AnotherCompanyId { get; set; } // References CompanyId
public int AndAnotherCompanyId { get; set; } // References CompanyId
public Company Company { get; set; }
}
public class Company
{
public int CompanyId { get; set; }
public string CompanyName { get; set; }
public string Address { get; set; }
}
I'm obviously missing something here.
How can I get the names of the other companies in my Model?
Any help is greatly appreciated.
The model is a viewmodel mapped to an EF POCO
I think you are confusing the notion of a view model. A view model is a class that is specifically designed to meet the requirements of your view. So if in your view you need to display the company name and not the company id then your view model should directly contain a CompanyName property. Or a reference to another view model (CompanyViewModel) which contains the name directly. It is then the responsibility of your controller action to query your domain models (EF entities) and aggregate them into a single view model tat will contain all the necessary information that the view requires.
Here's how a typical view model might look like:
public class MyViewModel
{
public CompanyViewModel Company { get; set; }
public CompanyViewModel AnotherCompany { get; set; }
public CompanyViewModel AndAnotherCompany { get; set; }
}
public class CompanyViewModel
{
public string Name { get; set; }
}
Where the data comes from in this view model is not important. You could have the Company property populated from your EF stuff, the AnotherCompany property populated from a XML file and AndAnotherCompany from WCF.
I have a database first model, where is a Person entity, like this:
public partial class Person
{
public System.Guid personID { get; set; }
public string firstName { get; set; }
public string lastName { get; set; }
public string sex { get; set; } // since in the DB it is char(1), default = 'F'
}
I defined a public enum for sex selection:
public enum Sex
{M, F}
which I want to use it to select the sex of the person and to render it as a radio button group.
I followed this solution: pass enum to html.radiobuttonfor MVC3 but couldn't make it work.
According to that answer, I added the RadioButtonForEnum extension, I extended my partial class with another property, like this:
public partial class Person
{
public System.Guid personID { get; set; }
public string firstName { get; set; }
public string lastName { get; set; }
public string sex { get; set; } // since in the DB it is char(1), default = 'F'
public Sex personSex { get; set; }
}
and changed my viewmodel and controller to use the enum.
Now I got the error:
The associated metadata type for type 'MyApp.Models.Person' contains the following unknown properties or fields: personSex. Please make sure that the names of these members match the names of the properties on the main type.
How can I fix this, since the model is derived from the database?