Is it possible to configure Ninject to not bind a dependency if it is already bound.
E.g.
If we load a module say called Client1 containing:
public class Client1Module:NinjectModule
{
public override void Load()
{
Bind<IService>.To<FancyService>()
}
}
Then we load a module called Base containing
public class BaseModule:NinjectModule
{
public override void Load()
{
Bind<IService>.To<BasicService>()
}
}
We would like to ensure that BasicService isn't bound and the system always uses FancyService. We won't know at design time whether FancyService exists. Client1 module is loaded if it is located.
I don't really want a bunch of repeitive boiler plate code around every injection etc. As there are 50-60 dependencies that all could be changed in Client modules.
Any ideas?
You have to make sure BaseModule is loaded after Client1Module:
public class BaseModule: NinjectModule
{
public override void Load()
{
if (!Kernel.GetBindings(typeof(IService)).Any())
{
Bind<IService>().To<BasicService>();
}
}
}
If I assume I load the base Module first and then load the Client Module after I think I can just use
Rebind<IService>.To<FancyService>()
It seems to work
Related
I'm studying blazor server.
Deployed a solution from a standard vs template.
Created two server-side services, TestService1 and TestService2.
In TestService1 i have task
GetMyData()
How can i call with task from TestService2?
If i trying
var serv1 = new TestService1()
i have to fill in all the variables of the constructor that is in TestService1.
What is easiest way?
In line with the comment on your question, the best way to go about this in Blazor is to utilize the built-in dependency injection mechanism.
I assume that your services look like the following:
public class TestService1
{
public object GetMyData()
{
}
}
public class TestService2
{
private readonly TestService1 _testService1 { get; set; }
public class TestService2(TestService1 ts1)
{
_testService1 = ts1;
}
public void DoesSomething()
{
var data = _testService1.GetMyData();
//...
}
}
First, you'd need to register these with Blazor at startup, so in your Startup.cs in the ConfigureServices method, add the following, assuming you have an empty constructor available for TestService1:
services.AddSingleton<TestService1>();
Because you'll need to instantiate an instance of TestService1 into TestService2 to call methods on it, you'll have to handle registration of TestService2 differently since you'll need to procure an instance of TestService1 from the DI service to instantiate it:
services.AddSingleton<TestService2>(s => {
var testService1 = s.GetService<TestService1>();
return new TestService2(testService1);
});
It's possible you may need to scope the services differently (e.g. used scoped instead of singletons). You can read about the differences here.
Now something is presumably calling TestService2 to kick all this off, so let's pretend it's running in a component in your Blazor app. You'd inject TestService2 into the component with the following:
#inject TestService2 _testService2
<h1>Hello!</h1>
#code {
protected override void OnInitialized()
{
_testService2.DoesSomething();
}
}
As part of the initialization then of this component, it'll automatically inject a TestService2 instance (based on the scoping you specified at DI initialization) to your component and will call the DoesSomething method on it. When injected, it looks to DI to instantiate the TestService1 service to the constructor as you've also specified, leaving it free to call that method and the call commences as intended.
Please let me know if you'd like any clarification somewhere!
I'm trying to understand the following code used in Nop Commerece task. It has classes which are implemented as below. The project is in the Plugins folder. One class implements ITask interface.
Public class foo:ITask
{
public void Execute()
{
......
}
}
Another implements BasePlugin, Iplugin
public class SmartWarehousePlugin : BasePlugin, IPlugin
{
public override void Install()
{
...
}
public override void Uninstall()
{
....
}
....
}
I understand the concept of Task and Plugin in NOP. I went through different tutorials. But I didn't find one where ITask and BasePlugin,IPlugin are used together. Why and when we need to do this?
As per my knowledge, ITask is an interface, using that you can create your own task in task scheduler and BasePlugin interface having install, uninstall methods , so using that methods, you can add custom things at installation/uninstallation.
Now the question are When? and Why? So, when you want to create/start your task just after plugin installation (or for similar kind of functionality) at that time you can use both together. Why part depends on your requirements.
We are using classes inheriting from Registry to configure our StructureMap container in our ASP.NET MVC 4 application startup.
Some excerpt from one of the registry-classes:
For<ISomeInterface>().HybridHttpOrThreadLocalScoped().Use<SomeImplementation>();
We would like use different instances of our interfaces depending on the context. (For example switching from database "online" mode to "maintenance" mode where everything is saved on filesystem; therefore using other interfaces (i.e. repositories) all over the place in our application)
For example by default it should use SomeImplementation but when passing some kind of querystring in the url (to name a simple "context" scenario) it should use SomeOtherImplementation.
How can this be achieved for multiple interfaces/types?
Should we use named instances for this? Like:
For<ISomeInterface>().HybridHttpOrThreadLocalScoped().Use<SomeOtherImplementation>().Named("other");
I read about StructureMap Profiles but i'm not sure if this is the right way to go.
Should we use profiles for this? Like i.e.:
Profile("other", profileExpression =>
{
For<ISomeInterface>().HybridHttpOrThreadLocalScoped().Use<SomeOtherImplementation>();
});
How can we switch different configurations on the fly?
ObjectFactory.Container.SetDefaultsToProfile("other");
This way? (At what stage in mvc "life-cycle" this can happen at the earliest?)
Can this be a temporary switch for just the current request or current users session?
Thanks in advance!
From my experience, runtime configuration like this is best achieved using an abstract factory that is responsible for creating your dependency during runtime.
This dependency can then be registered with StructureMap like so:
Your registry:
public class StorageRegistry : Registry
{
public StorageRegistry()
{
...
this.For<IDataStoreInstance>().Use(ctx => ctx.GetInstance<DataStoreAbstractFactory>().ConfigureStorage());
...
}
}
Now your DataStoreAbstractFactory is responsible for creating and configure the necessary storage instance based on your configuration. As DataStoreAbstractFactory is now registered with StructureMap you're able to inject the necessary dependencies into it for determining which storage method to use.
Implementation example:
public class DataStoreAbstractFactory
{
public DataStoreAbstractFactory()
{
// Dependencies to figure out data storage method can be injected here.
}
public IDataStoreInstance ConfigureStorage()
{
// This method can be used to return type of storage based on your configuration (ie: online or maintenance)
}
}
public interface IDataStoreInstance
{
void Save();
}
public class DatabaseStorage : IDataStoreInstance
{
public void Save()
{
// Implementation details of persisting data in a database
}
}
public class FileStorage : IDataStoreInstance
{
public void Save()
{
// Implementation details of persisting data in a file system
}
}
Usage:
Your controller/services or whatever are now completely unaware of what storage method they're using when accessing and persisting data.
public class UpdateController : Controller
{
public IDataStoreInstance StorageInstance { get; set; }
public UpdateController(IDataStoreInstance storageInstance)
{
StorageInstance = storageInstance;
}
[HttpPost]
public ActionResult Index()
{
...
this.StorageInstance.Save();
...
}
...
}
I recently read Phil Haack's post where he gives an example of implementing Model View Presenter for ASP.NET. One of the code snippets shows how the code for the view class.
public partial class _Default : System.Web.UI.Page, IPostEditView
{
PostEditController controller;
public _Default()
{
this.controller = new PostEditController(this, new BlogDataService());
}
}
However, here the view constructs the instance of the BlogDataService and passes it along to the presenter. Ideally the view should not know about BlogDataService or any of the presenter's lower layer dependencies. But i also prefer to keep the BlogDataService as a constructor injected dependency of the presenter as it makes the dependencies of the presenter explicit.
This same question has been asked on stackoverflow here.
One of the answers suggests using a service locator to get the instance of the BlogDataService and passing it along to the presenter's constructor.This solution however does not solve the problem of the view knowing about the BlogDataService and needing to explicitly get a reference to it.
Is there a way to automatically construct the presenter object using an IoC or DI container tool such that the view does not have to deal with explicitly creating the BlogDataService object and also injecting the view and service instances into the presenter's constructor. I prefer to use the constructor injection pattern as far as possible.
Or is there a better design available to solve the problem?. Can there be a better way to implement this If i am building a WinForms application instead of a ASP.NET WebForms application?
Thanks for any feedback.
Yes there is. For example using StructureMap in a webform constructor:
public partial class AttributeDetails : EntityDetailView<AttributeDetailPresenter>, IAttributeDetailView
{
public AttributeDetails()
{
_presenter = ObjectFactory.With<IAttributeDetailView>(this).GetInstance<AttributeDetailPresenter>();
}
....
}
and as you can see here presenter needs view and service injected
public AttributeDetailPresenter(IAttributeDetailView view, IAttributeService attributeService)
{
MyForm = view;
AppService = attributeService;
}
You can also use StructureMap BuildUp feature for webforms so that you can avoid using ObjectFactory directly in your view.
I did exactly this. The solution is based on Autofac, but can be implemented on top of any container.
First, define an interface representing the authority for presenting views in a request to the MVP system:
public interface IMvpRequest
{
void Present(object view);
}
Next, create a base page which has a property of that type:
public abstract class PageView : Page
{
public IMvpRequest MvpRequest { get; set; }
}
At this point, set up dependency injection for pages. Most containers have ASP.NET integration, usually in the form of HTTP modules. Because we don't create the page instance, we can't use constructor injection, and have to use property injection here only.
After that is set up, create event arguments representing a view which is ready to be presented:
public class PresentableEventArgs : EventArgs
{}
Now, catch the events in PageView and pass them to the request (present the page as well):
protected override bool OnBubbleEvent(object source, EventArgs args)
{
var cancel = false;
if(args is PresentableEventArgs)
{
cancel = true;
Present(source);
}
else
{
cancel = base.OnBubbleEvent(source, args);
}
return cancel;
}
protected override void OnLoad(EventArgs e)
{
base.OnLoad(e);
Present(this);
}
private void Present(object view)
{
if(MvpRequest != null && view != null)
{
MvpRequest.Present(view);
}
}
Finally, create base classes for each type of control you'd like to serve as a view (master pages, composite controls, etc.):
public abstract class UserControlView : UserControl
{
protected override void OnLoad(EventArgs e)
{
base.OnLoad(e);
EnsureChildControls();
RaiseBubbleEvent(this, new PresentableEventArgs());
}
}
This connects the control tree to the MVP system via IMvpRequest, which you'll now have to implement and register in the application-level container. The ASP.NET integration should take care of injecting the implementation into the page. This decouples the page entirely from presenter creation, relying on IMvpRequest to do the mapping.
The implementation of IMvpRequest will be container-specific. Presenters will be registered in the container like other types, meaning their constructors will automatically be resolved.
You will have some sort of map from view types to presenter types:
public interface IPresenterMap
{
Type GetPresenterType(Type viewType);
}
These are the types you will resolve from the container.
(The one gotcha here is that the view already exists, meaning the container doesn't create the instance or ever know about it. You will have to pass it in as a resolution parameter, another concept supported by most containers.)
A decent default mapping might look like this:
[Presenter(typeof(LogOnPresenter))]
public class LogOnPage : PageView, ILogOnView
{
// ...
}
I'm writing an app where 3rd party vendors can write plugin DLLs and drop them into the web app's bin directory. I want the ability for these plugins to be able to register their own HttpModules if necessary.
Is there anyway that I can add or remove HttpModules from and to the pipeline at runtime without having a corresponding entry in the Web.Config, or do I have to programmatically edit the Web.Config when adding / removing modules? I know that either way is going to cause an AppDomain restart but I'd rather be able to do it in code than having to fudge the web.config to achieve the same effect.
It has to be done at just the right
time in the HttpApplication life cycle
which is when the HttpApplication
object initializes (multiple times,
once for each instance of
HttpApplication). The only method
where this works correct is
HttpApplication Init().
To hook up a module via code you can
run code like the following instead of
the HttpModule definition in
web.config:
public class Global : System.Web.HttpApplication
{
// some modules use explicit interface implementation
// by declaring this static member as the IHttpModule interface
// we work around that
public static IHttpModule Module = new xrnsToashxMappingModule();
public override void Init()
{
base.Init();
Module.Init(this);
}
}
All you do is override the HttpApplication's Init() method and
then access the static instance's Init
method. Init() of the module hooks up
the event and off you go.
Via Rick Strahl's blog
Realize this is an old question, but asp.net 4 provides some new capabilities that can help here.
Specifically, ASP.NET 4 provides a PreApplicationStartMethod capability that can be used to add HttpModules programmatically.
I just did a blog post on that at http://www.nikhilk.net/Config-Free-HttpModule-Registration.aspx.
The basic idea is you create a derived HttpApplication that provides ability to add HttpModules dynamically at startup time, and it then initializes them into the pipeline whenever each HttpApplication instance is created within the app-domain.
The dll Microsoft.Web.Infrastructure.dll has a method for this inside the class DynamicModuleUtility.
The dll is shipped with WebPages 1.0
public static class PreApplicationStartCode
{
private static bool _startWasCalled;
public static void Start()
{
if (_startWasCalled) return;
_startWasCalled = true;
DynamicModuleUtility.RegisterModule(typeof(EventTriggeringHttpModule));
}
}
This worked for me for dynamic registration.
RegisterModule(typeof(RequestLoggerModule));
public class RequestLoggerModule : IHttpModule
{ ... }
https://learn.microsoft.com/en-us/dotnet/api/system.web.httpapplication.registermodule?view=netframework-4.7.2
In new versions of ASP MVC you can use Package Manager to add a reference to WebActivatorX and then do something like this
using WhateverNameSpacesYouNeed;
[assembly: WebActivatorEx.PreApplicationStartMethod(typeof(YourApp.SomeNameSpace.YourClass), "Initialize")]
namespace YourApp.SomeNameSpace
{
public static void Initialize()
{
DynamicModuleUtility.RegisterModule( ... the type that implements IHttpModule ... );
}
}