I made an MVC project which includes CRUD operations to all my classes, using default controllers and view pages which support those operations.
My new task was to make few API controllers to specific classes, which I have done correctly so far.
The problem is when a get request is requested, an entire object is returned with all its connections to other classes (which is correct!), but say I have this class:
public class VM{
public int Id { get; set; }
public string MacAddress { get; set; }
public string IpAddress { get; set; }
public DateTime? CreateDate { get; set; }
public string PrivateKey { get; set; }
public int AppId { get; set; }
public int CompanyId { get; set; }
}
I don't want the user to get the privateKey for instance, or ID. I would like the user to get all the rest, but certain information should NOT be sent.
What is the best practice to achieve that? Will making a new class which does not have those specific class members be the right answer?
Say tomorrow I would like to add another data member which will not be sent, will I have to make ANOTHER class?
I assume changing those specific data members' data to null just before sending the object back to the client is not the right answer, is it?
Just setting them to null is not the right answer indeed.
But generally you want your application to be as consistent as possible, and thus, for similar request you should return about the same types of fields/objects.
Thus a few (2 or 3) DTO (data transfer objects) should be sufficient.
If the project is of a small scale, or you just feel like being crazy you can always convert them to anonymous objects as follows:
List<VM> VMs = VMRepo.GetAll();
vms.ConvertAll(vm => new {vm.MacAddress, vm.IpAddress});
Or even give then custom names:
vms.ConvertAll(vm=> new {MAC= vm.MacAddress, IP= vm.IpAddress});
Related
I've googled some around the internet and found some articles about the subject, but none of them satisfied me. I want to know is it good to use object-object mapper to map objects to each other? I know it depends on situation to use, but how will I realize a good or best situation to use?
Taking a step back, it's best practice to separate data transfer objects (DTOs) and view models (VMs) from business objects (entities and alike). Mapping libraries, in that regard, are a means to an end and simply make that association easier.
As far as when, that's up to you. If you feel like you can convert between your business models and DTO/VMs in a way that's easy to maintain, go ahead. From my personal experience, that only goes so far (especially as the requirements change). Therefore, I'm fond of mapping libraries (specifically AutoMapper as I've come to know it's API and am comfortable plugging it in).
Having said that, any time I have to go between these two models I use AutoMapper. I simply configure it once and I'm off and running. Additional tweaks to the models (on either side) then become easier as I can change those bindings in one place (map definition file) and methods automatically "catch up".
Example:
My database contains a Record for a product:
class Product
{
public int Id { get; set; }
public string Description { get; set; }
public string Name { get; set; }
public double Price { get; set; }
public int QuantityOnHand { get; set; }
public int? ReorderQuantity { get; set; }
public string Sku { get; set; }
}
I may present this to the UI in a more distilled format:
public class ProductViewModel
{
public int Id { get; set; }
public string Description { get; set; }
public string Name { get; set; }
public double Price { get; set; }
public int Quantity { get; set; }
}
If this came from a repository of some kind, I'm simply calling:
var model = Mapper.Map<ProductViewModel>(productFromRepository)
Here I consistently get the view model I care about from the Product I've requested. If the business/service layer were to add/change/remove properties, I'd only go back to my Mapper.CreateMap<Product, ProductViewModel>() defintion, but the rest of my presentation logic would remain in-tact.
In addition to #Brad Christie's answer, automapping types which have minor differences into a single overarching type is generally easier if you are meaning to display them on your view alongside other products that are generated different ways.
If you'll allow me to crib off one my own previous answers, here's an example:
class SingleProduct {
string Name {get;set;}
decimal Price {get;set;}
decimal GetActualPrice() { return Price; }
}
class ComboSaleProduct {
string Name {get;set;}
List<SingleProduct> ComboProducts {get;set;}
decimal GetActualPrice() { return ComboProducts.Sum(p => p.GetActualPrice()); }
}
class ProductViewModel {
string Name {get;set;}
decimal ActualPrice {get;set;}
}
Automapper wires everything together so that you can return either of these and it will automatically map the "GetActualPrice" to ActualPrice on your viewmodel.
I have an MVC app using EF code first. I add a user to the system and enter pension details, part of this is a dropdown linked to a model called PensionBenefitLevel. This is the model -
[Key]
public int PensionBenefitLevelID { get; set; }
public string DisplayText { get; set; }
public int EmployeePercentage { get; set; }
public int EmployerPercentage { get; set; }
public virtual ICollection<Pension> Pension { get; set; }
When registered I have the PensionBenefitLevelID that came from the dropdown, but in my controller I was to peform a calculation using the EmployerPercentage value that is related to that ID. Can anyone point me in the correct direction?
Do I need to create a variable in the controller and use a linq query to get that value back? I've not been able to find any examples of something similar so if you could point me to one that would be great too.
If I understand the question correctly, you want to get back the entity corresponding to PensionBenefitLevelID and perform a calculation on the EmployerPercentage field.
Since you haven't mentioned what pattern you are using with EF (repository, unit of work, etc.) I can only give you a general answer:
var entity = [Your DB Context].[Your Entity].GetById(pensionBenefitLevelID);
if(entity != null)
{
[Calculation]
}
I am trying to send a simple object (AjaxSubmission) from a form to a Web API controller used to edit tables.
AjaxSubmission always has the same fields. One field, "data" refers to another simple object with accessors for the specific table (Employees or Vendors examples below).
public class AjaxSubmission
{
public string action { get; set; }
public string table { get; set; }
public string id { get; set; }
// ...
//// The following may be any other custom class
public Employees data { get; set; } // Could be Vendors or whatever
}
// Stored in AjaxSubmission (or so I hope)
public class Employees
{
public string name { get; set; }
public float salary { get; set; }
public long id { get; set; }
}
// Stored in AjaxSubmission
public class Vendors
{
public string dba { get; set; }
public int accountNum { get; set; }
public int zipcode { get; set; }
}
My controller gets the data like so:
public EditorServerResponse Put(AjaxSubmission ajaxSubmission = null) {
// Handle the data
}
When I make "data" an Object or Dynamic, it shows up as an empty object. I can't "as" it to Employees or Vendors because it doesn't store anything.
I suspect this is a limitation of the serializer. MVC4 uses JSON.NET for JSON, but the data is sent as "Content-Type: application/x-www-form-urlencoded; charset=UTF-8".
I cannot easily change the way data is sent because that is how the Datatables editor plug-in does its business. I think it's a reasonable way to send data and a reasonable problem for .NET to be able to handle.
I can get the data I need if I make a distinct class for each data type that AjaxSubmission might contain, but each would be a duplicate other than one line of code. That horribly violates the DRY principle.
My question is: How can I send AjaxSubmission without Repeating Myself? Is .NET capable of such a thing?
Edit:
Fiddler says the data looks like:
action edit
table
id row_4
data[amu] 49
data[chemicalFormula] BF2
data[commonName] Boron difluoride
data[status] Y
data[notes]
The raw data is:
action=edit&table=&id=row_4&data%5Bamu%5D=49&data%5BchemicalFormula%5D=BF2&data%5BcommonName%5D=Boron+difluoride&data%5Bstatus%5D=Y&data%5Bnotes%5D=
(This is different from my simplified examples but similar)
Am having trouble finding a clear answer to my situation when searching Stack Overflow and Google, hopefully someone can point me in the right direction.
My Situation
I want to be able to use a single edit form (in a single View) to update a 3-level-deep hierarchical entity using ASP.NET MVC 3 and Entity Framework 4 CTP (Code-first) - the model consists of Services, which can have many Service Options, which in Turn can have many Inventory Items.
I was expecting to be able to use MVCs default model binder (via TryUpdateModel) to:
Update an existing 'Service' record
Add/Update/Delete 'Service Option' records (attached to the Service) depending on posted values
Add/Update/Delete 'Inventory' records (attached to each Service Option) depending on posted values
My Model
[Bind(Include="Name, ServiceOptions")]
public class Service {
[Key]
public int ServiceID { get; set; }
public string Name { get; set; }
public DateTime DateCreated { get; set; }
public virtual ICollection<ServiceOption> ServiceOptions { get; set; }
}
[Bind(Include="ServiceOptionID, Description, Tags")]
public class ServiceOption {
[Key]
public int ServiceOptionID { get; set; }
public int ServiceID { get; set; } /* parent id reference */
public string Description { get; set; }
public virtual ICollection<Inventory> InventoryItems { get; set; }
}
[Bind(Include = "InventoryID, Description")]
public class Inventory {
[Key]
public int InventoryID { get; set; }
public int ServiceOptionID { get; set; } /* parent id reference */
public string Description { get; set; }
}
Ideal Controller Method:
[HttpPost]
public ActionResult EditService(int id) {
Service service = db.Services.Single(s => s.ServiceID == id);
TryUpdateModel(service); // automatically updates child and grandchild records
if (ModelState.IsValid) {
db.SaveChanges();
return RedirectToAction("Index");
}
return View(service);
}
Is there a way to achieve this utopian dream, or am I barking up the wrong tree? I'm open to using another technology (such as normal EF4, Automapper etc)
Thanks in advance!
With just the default model binder? Probably not.
With a custom one? Probably.
However your issue won't be the model binder itself. Your issue will be that EF and ORMs and ( I think ) in general do not consider removing an item from a collection as a delete operation. In effect what you are telling the ORM is the relationship does not exist, not that a child row needs to be deleted. Depending on your mappings you'll usually get an error like "A referential integrity constraint violation occurred". This won't be because of code first this is just how EF works.
EF works this way by design and is really important for more complex relationships such as when you have m2m relationships which reference other m2m relationships. You really want EF to be able to disambiguate calls for removal of a relationship and calls to remove a row entirely.
Also, IMHO, this technique is also bad because your letting the piece of code responsible for mapping http values also dictate how objects should be persisted. This is a bad move. I consider delete operations a pretty sacrosanct act and shouldn't be left to the ModelBinder alone. Without soft deletes or logging deleting objects should be considered "serious business".
This is somewhat a two-part question (please let me know if they should be split up).
1) I have a model class with an array of objects contained inside it. I would like to be able to bind this automatically so I can accept a single pollModel argument in my controllers.
public class pollResponseModel
{
public long id { get; set; }
public long pollID { get; set; }
public string text { get; set; }
public long count { get; set; }
}
public class pollModel
{
public long id;
public long entID { get; set; }
public string question { get; set; }
public DateTime posted { get; set; }
public DateTime expiration { get; set; }
public pollResponseModel[] responses { get; set; }
}
The problem is that I'm not sure how to bind the responses field, seeing as it can be any arbitrary size. Well, I can bind it properly when displaying the edit view, but that's about it. That leads me to the second part of my question:
2) What's an acceptable way of dynamically creating and removing data in a list on the client, so that it can be bound to a model and accessed in its modified form on the server? I envision the creation/removal process working like the iPhone list GUI: a single + button will add a new element, and a - button on each row of data will remove it from the list. I would imagine jQuery is an appropriate starting point but my JS skills are very limited.
Check out this article by Phil Haack : Model Binding To a List. It explains exactly what you need to do to bind to list properties, or properties that are complex objects.
Essentially you just have to construct your POST data in the correct way for the model binder to parse it. The article explains how to add hidden index fields and represent your complex properties in your form.