I need to add a global filter to a repository entity, i.e. it has to be applied everywhere this entity is accessed on Application service layer. My filter contains two conditions. Whereas adding the first condition, which depends on a constant, is easy and applied in OnModelCreating using HasQueryFilter, I have no idea how to apply automatically the second one, which depends on the currently selected (or default) UI language.
Use dependency injection via constructor in your DbContext class. Set the currently selected UI language inside the class implementing the interface. Use the injected implementation in the OnModelCreating method to apply the filter globally with .HasQueryFilter() method like you normally would.
If you're using something like a .NET Core API, you could build a middleware that determines the language of the current incoming request. I guess the same will work for MVC too.
Related
I have a working project with the following layers:
DataAccess - The project hits multiple DBs and web services. This layer defines the interfaces to each of them. It exposes the native types for each source (EF types for DBs, SOAP-defined types for web services, etc.). Let's say it exposes an EFProject and SoapProject.
Repository - This layer stiches results from the various sources to form a single entity, and exposes it. Let's call this ModelProject
Service - Adds REST attributes to to the entity (action links, etc.). This exposes a ProjectDTO.
WebApi - The controller spits out the ProjectDTO directly.
I'm trying to implement OData, specifically to page the results of very large queries. I've read a lot of examples, but they all seem to expose the source objects directly, and then map them to the final DTOs in the controller.
I would like to somehow push the ODataQueryOptions down to the Repository. This would allow me to keep the existing structure, and pass the query logic down to SQL. I understand that, because the ODataQueryOptions reference the ProjectDTO type, they can't be applied until an object of that type is available. Is there a way to "translate" the ODataQueryOptions from one type to another? Is there another way of doing this that I'm not aware of?
It is able to change the ODataQueryOptions, and such actions in a controller are for you to handle the options yourself:
public IQueryable Get(ODataQueryOptions queryOptions)
public IQueryable Get(int key, ODataQueryOptions queryOptions)
Here is a sample about this:
https://aspnet.codeplex.com/SourceControl/latest#Samples/WebApi/OData/v4/ODataQueryableSample/Controllers/OrdersController.cs .
For your reference, the source code of ODataQueryOptions is: https://aspnetwebstack.codeplex.com/SourceControl/latest#src/System.Web.OData/OData/Query/ODataQueryOptions.cs
Is there a way to "translate" the ODataQueryOptions from one type to another? Is there another way of doing this that I'm not aware of?
There is a way to actually translate the IQueryable<DomainModel> to IQueryable<DtoModel>.
I've done something similar in the past by leveraging AutoMapper's projection functionality. By calling the Project<TSource>/To<TTarget> methods, you can change an IQueryable that points to your domain models to another IQueryable that targets the Dto models, without actually executing it.
This means that you can now perform any OData operations on the DTO level and they will transfer through projection to the DAL layer into EntityFramework and SQL. In a scenario like this, there shouldn't be any need to manually handle the query logic so you can just use [EnableQuery] on the API route and let OData do its thing on the resulting IQueryable<DtoModel>.
I used this very successfully in one of the projects I worked on: as long as you rely just on AutoMapper projection to convert the types, it should work fine.
Granted, you can't do a lot of fancy mapping that way. The project methods will not be able to apply all kinds of mappings that you create, so I recommend checking the documentation on that front.
You also have to keep in mind that the original IQueryable needs to be exposed outside of the repository layer for this to work properly, otherwise the query will be executed too early. Some people will find that a boundary violation and will advocate for materializing the query inside the repository layer, but I don't have an issue with that particular aspect.
I'm writing my first GWT-Application and need your advice. I have no problems implementing a locator for database entities where I can reuse the version-column used for optimistic locking by hibernate, but one of my entities represents a ldap-Object. Can you tell me what the method getVersion() of the Locator is used for and how I can implement this method for my ldap-Object? I will do read and write ldap objects.
From GWT documentation, getVersion method is
Used by RequestFactory to infer if an entity has changed. The backing store (JDO, JPA, etc.) is responsible for updating the version each time the object is persisted, and RequestFactory calls getVersion() to learn of changes. This information is used in two places. First, the RequestFactoryServlet sends an UPDATE event to the client if an entity changes as a result of the method invocation on the server, for example, when a call to persist an editable entity results in an updated version on the server. Second, the client maintains a version cache of recently seen entities. Whenever it sees an entity whose version has changed, it fires UPDATE events on the event bus so that listeners can update the view.
Since many persistence frameworks offer generic find/get/query methods, it's also possible to create a generic Locator class and specify it in the #ProxyFor annotation for each entity type. To do this, all your entities can extend a base class that provides getId() and getVersion(). Alternatively, the generic Locator can use reflection to call getId() and getVersion() when needed.
Not sure if you're looking for anything else in addition to this.
I have the same problem. My first thought was to use the Attribute modifyTimestamp and createTimestamp. But there is still a functional gap:
The smallest unit of These timestamps is seconds so a Change in the same second can not be detected. Another solution would be to use a kind of checksum over all attributes of the ldap object. Not very nice..
I'm using DataAnnotations for validation of a custom class (LINQ to SQL auto generated) using the MetadataType tag on top of the class. I'm loving DataAnnotations and it works well in simple, common scenarios. E.g.
[MetadataType(typeof(Person_Validation))]
public class Person
But what if you need to have two different sets of validation rules applied to the class in different scenarios???
My situation: Some fields are mandatory on the www public-facing site, but not mandatory on the internal admin site. But both sites have a View which "Creates New" of the same object/class.
This is where it becomes DataAnnotations HELL surfaces..
I've tried using two different ViewModels with different validation applied to each of them, two classes that inherit from Person with different validation applied to each of them. But all roads seem to conflict with DRY principals and you end up somewhere along the line having the totally respecify all properties for the underlying class structure. You don't have to do this when you just have one validation rule set. So it very quickly becomes hell and not practical for complex objects.
Is this possible using DataAnnotations and what is the best DRY architecture?
Not sure what you mean by 'virtually duplicate and manually set each and every property manually in the original underlying class'. I've never liked the idea of buddy classes, and would personally recommend different view models for Admin and Public site (with appropriate validation set on each), and then mapping between the models using AutoMapper.
UPDATE:
Regading Automapper, the basic usage is something like this:
First you have to define your mappings. This lets automapper figure out in advance how to map objects. You only need to do this once in the application, so a good place to do this in an ASP.NET app is in Application_Start() in Global.asax. For each pair of classes you want to map between, call: Mapper.CreateMap<SourceType, DestinationType>();
Then, in your application code to do the map you just use:
var destinationObject = Mapper.Map<SourceType, DestinationType>(sourceOjbect);
Class Engine has "start(c:Component)" method. So do we need to draw an association between Engine and Component Class IF there is no "new Component()" inside Engine class.
No, you do not in general need to have an association to a type even if the type is mentioned in a parameter. It entirely depends on if the state of an Engine maintains a relationship with one or more Components.
If the Component you passed around is only use locally in method start, then there is no real association that persists from one state (one method call) to the next.
This is not an association, it´s a dependency relationship between the two. A dependency means that if the dependee (the Component in your case) changes the depender (the Engine) may become affected (maybe Engine::start was using a Component method that it is no longer available or that has changed its parameters)
I would like to experimentally apply an aspect of encapsulation that I read about once, where an entity object includes domains for its attributes, e.g. for its CostCentre property, it contains the list of valid cost centres. This way, when I open an edit form for an Extension, I only need pass the form one Extension object, where I normally access a CostCentre object when initialising the form.
This also applies where I have a list of Extensions bound to a grid (telerik RadGrid), and I handle an edit command on the grid. I want to create an edit form and pass it an Extension object, where now I pass the edit form an ExtensionID and create my object in the form.
What I'm actually asking here is for pointers to guidance on doing this this way, or the 'proper' way of achieving something similar to what I have described here.
It would depend on your data source. If you are retrieving the list of Cost Centers from a database, that would be one approach. If it's a short list of predetermined values (like Yes/No/Maybe So) then property attributes might do the trick. If it needs to be more configurable per-environment, then IoC or the Provider pattern would be the best choice.
I think your problem is similar to a custom ad-hoc search page we did on a previous project. We decorated our entity classes and properties with attributes that contained some predetermined 'pointers' to the lookup value methods, and their relationships. Then we created a single custom UI control (like your edit page described in your post) which used these attributes to generate the drop down and auto-completion text box lists by dynamically generating a LINQ expression, then executing it at run-time based on whatever the user was doing.
This was accomplished with basically three moving parts: A) the attributes on the data access objects B) the 'attribute facade' methods at the middle-tier compiling and generation dynamic LINQ expressions and C) the custom UI control that called our middle-tier service methods.
Sometimes plans like these backfire, but in our case it worked great. Decorating our objects with attributes, then creating a single path of logic gave us just enough power to do what we needed to do while minimizing the amount of code required, and completely eliminated any boilerplate. However, this approach was not very configurable. By compiling these attributes into the code, we tightly coupled our application to the datasource. On this particular project it wasn't a big deal because it was a clients internal system and it fit the project timeline. However, on a "real product" implementing the logic with the Provider pattern or using something like the Castle Projects IoC would have allowed us the same power with a great deal more configurability. The downside of this is there is more to manage, and more that can go wrong with deployments, etc.