Can a Post method take parameters from the Query String?

YES is the answer (if you are in hurry to leave the site); and adding a keyword [FromUri] before model param in action method is the trick to do it.

How It Works:

If you have a model Foo:

public class Foo
{
public string Bar { get; set; }
public int Baz { get; set; }
}

And you want to bind this from the query string, then you must address the individual properties:

?Bar=qux&Baz=42

And annotate that the model must be bound from the query string:

public void Bar([FromUri]Foo foo)
{
  //your intelligent code goes here..
}

 

And if you want to send JSON into your action method and not a model, simply bind to a string instead of a model. In action method you can deserialize this string to a json model or key-value pair and then can do whatever you want with the JSON string inside your action method.

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Dependency Injection in ASP.NET Web API 2

What is Dependency Injection?

A dependency is any object that another object requires. For example, it’s common to define a repository that handles data access. Let’s illustrate with an example. First, we’ll define a domain model:

public class Product
{
    public int Id { get; set; }
    public string Name { get; set; }
    public decimal Price { get; set; }
}

Here is a simple repository class that stores items in a database, using Entity Framework.

public class ProductsContext : DbContext
{
    public ProductsContext()
        : base("name=ProductsContext")
    {
    }
    public DbSet<Product> Products { get; set; }
}

public class ProductRepository : IDisposable
{
    private ProductsContext db = new ProductsContext();

    public IEnumerable<Product> GetAll()
    {
        return db.Products;
    }
    public Product GetByID(int id)
    {
        return db.Products.FirstOrDefault(p => p.Id == id);
    }
    public void Add(Product product)
    {
        db.Products.Add(product);
        db.SaveChanges();
    }

    protected void Dispose(bool disposing)
    {
        if (disposing)
        {
            if (db != null)
            {
                db.Dispose();
                db = null;
            }
        }
    }

    public void Dispose()
    {
        Dispose(true);
        GC.SuppressFinalize(this);
    }
}

 

Now let’s define a Web API controller that supports GET requests for Product entities. (I’m leaving out POST and other methods for simplicity.) Here is a first attempt:

public class ProductsController : ApiController
{
    // This line of code is a problem!
    ProductRepository _repository = new ProductRepository();

    public IEnumerable<Product> Get()
    {
        return _repository.GetAll();
    }

    public IHttpActionResult Get(int id)
    {
        var product = _repository.GetByID(id);
        if (product == null)
        {
            return NotFound();
        }
        return Ok(product);
    }
}

 

Notice that the controller class depends on ProductRepository, and we are letting the controller create the ProductRepository instance. However, it’s a bad idea to hard code the dependency in this way, for several reasons.

  • If you want to replace ProductRepository with a different implementation, you also need to modify the controller class.
  • If the ProductRepository has dependencies, you must configure these inside the controller. For a large project with multiple controllers, your configuration code becomes scattered across your project.
  • It is hard to unit test, because the controller is hard-coded to query the database. For a unit test, you should use a mock or stub repository, which is not possible with the currect design.

We can address these problems by injecting the repository into the controller. First, refactor the ProductRepository class into an interface:

public interface IProductRepository
{
    IEnumerable<Product> GetAll();
    Product GetById(int id);
    void Add(Product product);
}

public class ProductRepository : IProductRepository
{
    // Implementation not shown.
}

Then provide the IProductRepository as a constructor parameter:

public class ProductsController : ApiController
{
    private IProductRepository _repository;

    public ProductsController(IProductRepository <span class="hiddenGrammarError" pre="">repository)  
    {
        _repository</span> = repository;
    }

    // Other controller methods not shown.
} 

This example uses constructor injection. You can also use setter injection, where you set the dependency through a setter method or property.

But now there is a problem, because your application doesn’t create the controller directly. Web API creates the controller when it routes the request, and Web API doesn’t know anything about IProductRepository. This is where the Web API dependency resolver comes in.

The Web API Dependency Resolver

Web API defines the IDependencyResolver interface for resolving dependencies. Here is the definition of the interface:

public interface IDependencyResolver : IDependencyScope, IDisposable
{
    IDependencyScope BeginScope();
}

public interface IDependencyScope : IDisposable
{
    object GetService(Type serviceType);
    IEnumerable<object> GetServices(Type serviceType);
}

The IDependencyScope interface has two methods:

  • GetService creates one instance of a type.
  • GetServices creates a collection of objects of a specified type.

The IDependencyResolver method inherits IDependencyScope and adds the BeginScope method. I’ll talk about scopes later in this tutorial.

When Web API creates a controller instance, it first calls IDependencyResolver.GetService, passing in the controller type. You can use this extensibility hook to create the controller, resolving any dependencies. If GetService returns null, Web API looks for a parameterless constructor on the controller class.

Dependency Resolution with the Unity Container

Although you could write a complete IDependencyResolver implementation from scratch, the interface is really designed to act as bridge between Web API and existing IoC containers.

An IoC container is a software component that is responsible for managing dependencies. You register types with the container, and then use the container to create objects. The container automatically figures out the dependency relations. Many IoC containers also allow you to control things like object lifetime and scope.

“IoC” stands for “inversion of control”, which is a general pattern where a framework calls into application code. An IoC container constructs your objects for you, which “inverts” the usual flow of control.

For this tutorial, we’ll use Unity from Microsoft Patterns & Practices. (Other popular libraries include Castle Windsor, Spring.Net, Autofac, Ninject, and StructureMap.) You can use NuGet Package Manager to install Unity. From the Tools menu in Visual Studio, select Library Package Manager, then select Package Manager Console. In the Package Manager Console window, type the following command:

Install-Package Unity

Here is an implementation of IDependencyResolver that wraps a Unity container.

using Microsoft.Practices.Unity;
using System;
using System.Collections.Generic;
using System.Web.Http.Dependencies;

public class UnityResolver : IDependencyResolver
{
    protected IUnityContainer container;

    public UnityResolver(IUnityContainer container)
    {
        if (container == null)
        {
            throw new ArgumentNullException("container");
        }
        this.container = container;
    }

    public object GetService(Type serviceType)
    {
        try
        {
            return container.Resolve(serviceType);
        }
        catch (ResolutionFailedException)
        {
            return null;
        }
    }

    public IEnumerable<object> GetServices(Type serviceType)
    {
        try
        {
            return container.ResolveAll(serviceType);
        }
        catch (ResolutionFailedException)
        {
            return new List<object>();
        }
    }

    public IDependencyScope BeginScope()
    {
        var child = container.CreateChildContainer();
        return new UnityResolver(child);
    }

    public void Dispose()
    {
        container.Dispose();
    }
}

If the GetService method cannot resolve a type, it should return null. If the GetServices method cannot resolve a type, it should return an empty collection object. Don’t throw exceptions for unknown types.

Configuring the Dependency Resolver

Set the dependency resolver on the DependencyResolver property of the global HttpConfiguration object.

The following code registers the IProductRepository interface with Unity and then creates a UnityResolver.

public static void Register(HttpConfiguration config)
{
    var container = new UnityContainer();
    container.RegisterType<IProductRepository, ProductRepository>(new HierarchicalLifetimeManager());
    config.DependencyResolver = new UnityResolver(container);

    // Other Web API configuration not shown.
}

Dependenecy Scope and Controller Lifetime

Controllers are created per request. To manage object lifetimes, IDependencyResolver uses the concept of a scope.

The dependency resolver attached to the HttpConfiguration object has global scope. When Web API creates a controller, it calls BeginScope. This method returns an IDependencyScope that represents a child scope.

Web API then calls GetService on the child scope to create the controller. When request is complete, Web API calls Dispose on the child scope. Use the Dispose method to dispose of the controller’s dependencies.

How you implement BeginScope depends on the IoC container. For Unity, scope corresponds to a child container:

public IDependencyScope BeginScope()
{
    var child = container.CreateChildContainer();
    return new UnityResolver(child);
}

Credit:

Thanks Mike Wasson(Mike Wasson is a programmer-writer at Microsoft) this injection. And yes you originally published this post(which is 100% yours till dinosaur appear again on earth.) on Asp.Net 🙂

MVC Recommended Resources And Tutorials

The articles and links below are a confronting effort of Rick Anderson, he works as a programmer writer for Microsoft, and mainly deals with Asp.net MVC, Azure and Entity Framework. You may find him tweeting something useful: @RickAndMSFT

Getting Started with ASP.NET MVC

New Featured Content

Microsoft Azure

Security

Membership, Authentication

OWIN and Katana

Data Access in ASP.NET MVC

Web Forms to MVC

Performance

AngularJS, Knockout, KnockoutJS

jQuery, Ajax, JSON, JavaScript

HTML5

Routing

Globalization, Internationalization and Localization

Azure and ASP.NET MVC

Mobile

Single Page Application (SPA)

Twitter, Facebook

Unit Testing , TDD, Repository Pattern and Unit of Work

Best Practices

Deployment

Rich text Editors for MVC

General

Forum Posts

How To Render HTML Views Asp.Net MVC

Asp.Net by default serves views with .cshtml extension, that makes it possible to use various Asp.net inbuilt functions and html helpers to used with it. But sometime the facilities to make coding easier sucks.

Situation 1

I have setup a project to use Asp.net MVC/Web API using C# and using AngularJs for binding views at front-end. Now as I get the data from my controllers using $http of angularjs I want to ibnd it on my view using angular, and to get this done I create pure HTML view in Views Folder of MVC project. And when I compile… Oops!!

Situation Something Else

I may have some static files in my view folders and I really don’t want Asp.Net to compile those files for me, so I get it as .html extension, these are pure html content files now. And I go ahead and compile the project.. Oops again!

Reason

Asp.Net doesn’t serve pure html views from Views folder by default. We may have to tell compiler that we want to use pure html files from Views folder, once we ask it will do it for us.

Solution

How To Render HTML Views Asp.Net MVC
How To Render HTML Views Asp.Net MVC

.

We can add handler for the required extension to be served under System.Webserver tag in Web.config under Views  folder.

 <!-- web.config under the Views folder -->

<system.webserver>
<handlers>
<!-- handler for serving html view in mvc -->
<add name="HtmlScriptHandler" path="*.html" verb="*" precondition="integratedMode" type="System.Web.StaticFileHandler" />
</handlers>
</system.webserver>

.

If you don’t want to set a handler and just want to render the html view you can use File/ FilePathResult method:

 //return the file using FilePathResult method
 return new FilePathResult("path_to_file.html", "text/html");

 //return the file using File method
 return File("path_to_file.html", "text/html");