Odata: Mapping View Model to Domain Model - asp.net-mvc

I have an odata call that works properly the first time but fails during any successive call due to properties not matching. My controller has very little logic as it's just responsible for calling my domain service to query an Entity Framework database and returning the results as view models. However, when I try to sort I get an error because the hierarchy of my view model does not match my domain model.
Domain Model:
public class Parent
{
public object Child
{
public string Name
}
}
View Model:
public class Parent
{
public string ChildName
}
Using the above examples the EF query would return a list of Parents, which I would convert to view models to send off to the client. When a sort request is made on ChildName odata fails because Parent has no concept of ChildName. I need to map ChildName to Child.Name. I've seen examples of people using EntitySets to change the name but none that will map the model in my case.

I ended up using EF to convert my domain model to a view model using a LINQ expression during the query. Example but changed the view model to ParentView and added constructor:
var query = from p in context.Parent select new ParentView(p.Child.Name)
The positive of this is that it's all run on the database so I'm not transporting unnecessary data. Also, I am able to continue to use the odata options in the query since odata will add onto the query. However, I can't help but feel this is not the best way.

Related

Web API OData Actions with Entity as parameter

I have a requirement to encapsulate pieces of business logic within a transaction in an OData Web API service. Some of these pieces will need to accept one or more entities.
An example use case might be StockProduct and this might accept a Product entity and a Location entity. It would create the product and update stock records for the Location.
The approach I've taken is to create an unbound OData action that accepts these entities so that both of these can be operated on in a single transaction. Unfortunately neither can Entities be used as an ODataActionParameter nor can they be part of a class and used as a complex parameter.
I can think of a two ways around this:
Create a DTO class that is not an entity that is a mirror of each of my mirror classes and convert from DTO to Model within my action. The problem here is that I already have a DTO for each Model eg. Product.cs and ProductDTO.cs and don't really want to have to create a third class. (Currently, the ProductDTO.cs is used for Posts, Puts, Patches and Deletes and the Product.cs is used for Gets).
Abandon OData actions and create a simple end point that accepts whatever I like. I'm not keen on going down the second route as I'd like to use OData exclusively.
Any thoughts or suggestions?
You can use the ActionConfiguration.EntityParameter() method to bind an entity as a parameter to your OData action method.
Here is an example:
ActionConfiguration validate = ModelBuilder.EntityType<TEntity>()
.Collection.Action("Validate");
validate.Namespace = "Importation";
validate.EntityParameter<TEntity>(typeof(TEntity).Name);
validate.CollectionParameter<string>("UniqueFields");
validate.Returns<ValidationResult>();
However, note that the ModelState will not check against the content of the supplied Entity and will set any missing properties to null and properties exceeding the StringLength(x) annotation in your model will still pass. If you wish to validate the entity itself after, use this bit of code in your action method:
[HttpPost]
public virtual IHttpActionResult Validate(ODataActionParameters parameters)
{
//First we check if the parameters are correct for the entire action method
if (!ModelState.IsValid)
{
return BadRequest(ModelState);
}
else
{
//Then we cast our entity parameter in our entity object and validate
//it through the controller's Validate<TEntity> method
TEntity Entity = (TEntity)parameters[typeof(TEntity).Name];
Validate(Entity, typeof(TEntity).Name);
if (!ModelState.IsValid)
{
return BadRequest(ModelState);
}
IEnumerable<string> uniqueFields = parameters["UniqueFields"] as IEnumerable<string>;
bool result = Importer.Validate(Entity, uniqueFields);
return Ok(result);
}
}
As for your StockProductDTO, it seems to me that this is an new Business Entity by itself and should be treated as such.
You can use a batch request to perform multiple operations within a single request. This allows you to use your existing controllers for inserting your two objects.
https://aspnetwebstack.codeplex.com/wikipage?title=Web+API+Request+Batching

Repository pattern and lazy loading + AutoMapper

I've split my project into (as of this time) 4 layers:
Application (ASP.NET MVC project)
Domain/Model (contains only models with no logic in them at all)
BusinessLogic (right now only "wraps" the repositories)
DAL (Entity Framework, but should be interchangeable)
The MVC Controllers use the business logic "services" to talk to the database through whatever lies beneath the business logic layer, and the controller should not need to tell anyone that "I want this Student, and I also want all his Courses" - this implies that lazy loading should be used.
The thing is, if I just "call through" and return the result to whoever calls the controller action, I can't really control what gets loaded unless I explicitly access the properties on the model to trigger the loading of the graph.
I'd like to use AutoMapper to map from my model to a Dto (one for each model, which defines what gets returned).
Say I have a model like this:
public class Student
{
public string Name {get;set;}
public int Age {get;set;}
public ICollection<Course> Courses {get;set;}
}
And a dto like this:
public class StudentDto
{
public string Name {get;set;}
public ICollection<Course> Courses {get;set;}
}
When AutoMapper does the mapping, it doesen't appear to map the Courses, which is my problem.
Should I be eager-loading at the repository layer instead?
As you have in the Student and StudentDto Automapper should map object graph correctly to the dto. This will work only if lazy loading enabled otherwise you may need to use eager loading.
I think the best way to choose what method to use is to test the performance of both method which will depend on several factors like your data model in the db and the delay between the sql server and your application etc.. .
Edit.. How to choose the best method
How to choose the best method
You need to consider three things,
How many connections that you are going to make with the database. If you are using lazy loading there will be a database call for all the reference points of a navigation properties if referred navigation property is not in the context.
How much data that you are going to retrieve from databaseIf you choose to load all the data in initial query with differed loading it will be too slow when you have huge amount of data to retrieve.
Complexity of the query . When you are using lazy loading the queries will be simple because all the data is not loaded in the initial query. If you use immediate loading it will make quires will be more complex with query paths
read more here

Entity - Automatically Create MVC Controller with dropdown

There's probably a really basic answer to this question but I am new to Entity and MVC and am getting used to the basics.
I'm trying to automatically generate a MVC controller for the main table Sites with a dropdown for server. It seems like I would need a model like this:
public class Sites
{
public TTSites TTSites { get; set; }
public List<servers> server { get; set; }
public Sites()
{
server = new List<servers>();
}
}
This is using the classes TTSites and servers both with string server
But if I set this as my model class and my entity database as data context it says I need to define a key. Should I be using the base classes instead of the model or what? Do i need to set something up in the model or base class?
It seems like you've got some terminology confused. You code the controller actions in a controller class, and the routing engine determines what controller action to call based on the URL. For example, if you have a HomeController class with a default Index action, it might look like this:
public ActionResult Index()
{
// code here
}
This would be invoked with the default routing, if you went to your site with a URL like this (let's say your site can be hit via the www.mysite.com URL:
http://www.mysite.com/Home
That would get you into the Index action in the controller.
Ordinarily, one would use a view model to use on the UI side, and that would be populated from an entiy with the data you need in the view itself. If you had two entities like TTSite and Server, you'd populate the Sites view model like so, as a (very simple) example:
public ActionResult Index()
{
var servers = yourDbContext.Servers.ToList();
var ttSite = yourDbContext.TTSites.GetByID(1); // retrieve one entity by its ID value, this would be acquired dynamically based on some sort of user input rather than hard-coded
var viewModel = new Sites(servers);
viewModel.TTSite = ttSite;
return View(viewModel);
}
I'm not including anything regarding making drop-downs, just illustrating getting data into a view model and then creating a view with that view model.
Note that you would not use the Sites class as an entity but rather a view model, and setting its data based on entities from your database. You wouldn't be setting any primary keys in a view model class; those are the concern of the data model, and you've presumably already got those entities (such as TTSite) set up in a usable fashion in your data layer.
Once you've got a controller action and a view up and working, you can turn to getting the view model data into a form usable by a drop-down list, and going from there.

Using LLBL as Model in MVC

I have settled on trying to use ASP.NET MVC but the first part I want to replace is the Model. I am using LLBL Pro for the model.
I have a table called "Groups" that is a simple look up table. I want to take thhe results of the table and populate a list in MVC. Something that should be very simple... or so I thought.... I've tried all kinds of things as I was getting errors like:
The model item passed into the dictionary is of type 'System.Collections.Generic.List1[glossary.EntityClasses.GroupEntity]', but this dictionary requires a model item of type 'System.Collections.Generic.IEnumerable1[glossary.CollectionClasses.GroupCollection]'.
private GroupCollection gc = new GroupCollection();
public ActionResult Index()
{
gc.GetMulti(null);
return View( gc.?????? );
}
This is all I am trying to do, I've tried lots of variations, but my goal is simply to take the data and display it.
Not sure if this would work, but you could try wrapping the EntityCollection into a ViewModel class and passing it to the View like so:
public class GroupsViewModel()
{
public GroupCollection Groups { get; set; }
// other items in your view model could go here
}
then convert your controller method to
public ActionResult Index()
{
GroupCollection gc = new GroupCollection();
gc.GetMulti(null);
GroupsViewModel vm = new GroupsViewModel();
vm.Groups = gc;
return View(vm);
}
I like this approach because each ViewModel is an object in-and-of itself.
You can use the AsEnumerable extension where your ????? are or change the type of your ViewUserControl(in the markup) to be of type System.Collections.Generic.List. Basically what you need to correct is the mismatch between the type of the View and the Model being passed in.
I'm not sure about your exact error, but I'd venture a guess that one of two things are happenging:
You are making some sort of invalid / illegal call on your LLBLGen object. If this is the case make sure you are setting it up right / calling right method / property etc.
The model you are passing to the veiw is too hairy for it to deal with. In this case, and in general, you should create a light 'View Model' class with just the data you want displayed and populate it from your LLBLGen object first then pass it to the view, which will be able to easily handle your view model class.
Here are some references:
http://stephenwalther.com/blog/archive/2009/04/13/asp.net-mvc-tip-50-ndash-create-view-models.aspx
http://nerddinnerbook.s3.amazonaws.com/Part6.htm
http://www.codinginstinct.com/2008/10/view-model-inheritance.html
Stemming off what Yuriy said, it looks like your view is strongly typed to a "collection" of a collection of your groupentity, and you are trying to pass just the collection of your groupentities. Make sure your "collection" type (IEnumerable, IList, etc) matches what type of collection you are sending in your controller, along with the type of the actual object in the collection.
View:
System.Collections.Generic.List1[glossary.EntityClasses.GroupEntity]
Controller:
System.Collections.Generic.List1[glossary.EntityClasses.GroupEntity]
Just a thought

Inserting data based on ParentID, strange behavior ASP.NET MVC?

I have a simple form which inserts a new Category with the given parentID (ServiceID).
and my parent child relationship is this;
Service > Category
my url for creating a Category based on the ServiceId is this
/Admin/Categories/Create/3 => "3 is the serviceID"
and my Action method is this
[AcceptVerbs(HttpVerbs.Post)]
public ActionResult Create(int? id, Category category)
{
if (ModelState.IsValid)
{
try
{
category.Service = dbService.GetAll().WithServiceId(id.Value).SingleOrDefault();
dbCategory.Add(category);
dbCategory.Save();
return RedirectToRoute("List_Categories", new { ServiceId = id.Value });
}
catch
{
ModelState.AddRuleViolation(category.GetRuleViolations());
}
}
return
View ....
I am using LinqToSql for db actions. Anyway the strange part begins here.
When i save the data it inserts a data to Service table instead of insterting data just to Category Table and the data which is inserted to Category Table has the new inserted ServiceID.
Is it a problem with the ASP.NET MVC ModelBinder or am i doing a mistake that i dont see ?
I have used LinqToSql in several projects and have never had an issue like this
It could be an error in your LINQ To SQL set up. Is the service id an autogenerated field in the DB -- is it marked as such in the LINQ to SQL classes? Does your service disconnect it from the data context, then not reattach it before submitting? If so, have you tried adding the category to the service and then saving the updated service?
var service = ...
service.Categories.Add(category);
service.Save();
Where does your Category object come from? As I see you are relying on ASP.NET MVC Model binding for providing it but for that you need a form somewhere to make a POST. It would help to see the form too.
Also personally I rather use FormCollection (rather than business model classes) in my action signatures and then pull the posted data out from the FormCollection by myself. Coz sooner or later you end up having some complex objects with various one-to-many, many-to-many relationships that Model Binding just won't pick up and you have to construct it by yourself.

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