Tag Archives: ASP.Net

Getting Started with ASP.NET vNext

Article posted on Asp.Net vNext Overview

Getting Started with ASP.NET vNext
By
Mike Wasson |

The next version of ASP.NET (“ASP.NET vNext”) has been re-designed from the ground up. The goal is to create a lean and composable .NET stack for building modern cloud-based apps.

Here are some of the features of ASP.NET vNext:

  • vNext includes new cloud-optimized versions of MVC, Web API, Web Pages, SignalR, and Entity Framework.
  • MVC, Web API, and Web Pages will be merged into one framework, called MVC 6. The new framework removes a lot of overlap between the existing MVC and Web API frameworks. It uses a common set of abstractions for routing, action selection, filters, model binding, and so on. You can use the framework to create both UI (HTML) and web APIs.
  • ASP.NET vNext apps can use a cloud-optimized subset of .NET vNext. This subset is factored for server and web workloads, has a smaller footprint than the full .NET vNext, and supports side-by-side deployment.
  • MVC 6 has no dependency on System.Web. The result is a leaner framework, with faster startup time and lower memory consumption.
  • vNext will support true side-by-side deployment. If your app uses the cloud-optimized subset of .NET vNext, you can bin deploy all of your dependencies, including the .NET vNext (cloud optimized) packages. That means you can update your app without affecting other applications on the same server.
  • vNext is host agnostic. You can host your app in IIS, or self-host in a custom process. (Web API 2 and SignalR 2 already support self-hosting; ASP.NET vNext brings this same capability to MVC.)
  • Dependency injection is built into the framework. Use your preferred IoC container to register dependencies.
  • vNext uses the Rosyln compiler to compile code dynamically. You will be able to edit a code file, refresh the browser, and see the changes without rebuilding the project.
  • vNext is open source and cross platform.

In order to accomplish these goals, ASP.NET vNext contains breaking changes. The current frameworks (Web Forms 5, MVC 5, Web API 2, Web Pages 3, SignalR 2, and Entity Framework 6) will continue to ship in Visual Studio, and will be fully supported in .NET vNext.

This overview is designed to get you started with ASP.NET vNext. Because vNext is still an early preview, I won’t walk through creating an entire real-world application. Instead, I want to highlight some of the features and show enough code to get you started.

The overview assumes you are familiar with either MVC 5 or Web API 2. If not, here is some terminology that is used in ASP.NET MVC.

  • A controller handles HTTP requests and executes application logic.
  • Actions are methods on a controller that get invoked to handle HTTP requests. The return value from an action is used to construct the HTTP response.
  • Routing is the mechanism that selects which action to invoke for a particular HTTP request, usually based on the URL path and the HTTP verb.
  • A view is a component that renders HTML. Controllers can use views when the HTTP response contains HTML.
  • A model is an object that represents the domain data in your application. Typically an app either renders the model as HTML, or serializes the model into a data format such as JSON.
  • Razor syntax is a simple programming syntax for embedding server-based code in a web page.

I’ve defined some of these terms in a way that is specific to ASP.NET. For example, controllers have a particular purpose in ASP.NET MVC, but “model-view-controller” is a more general pattern, used by many frameworks.

Getting Started with ASP.NET vNext

Currently, there is no Visual Studio integration for ASP.NET vNext, so you will build and run applications from the command line.

Use kvm (the version manager) to get the latest version of the runtime. Follow the instructions on the project wiki.

A minimal vNext project contains two files:

  • project.json. This file lists the dependencies for the application.
  • A startup class.

For now, the best way to create a project.json file is to copy the example from HelloMvc sample.

The startup class is where you configure the HTTP request pipeline for your application. Here is a simple example.

using Microsoft.AspNet.Builder;

public class Startup
{
    public void Configure(IBuilder app)
    {
        app.UseWelcomePage();
    }
}

By default , the hosting environment expects the startup class to be named Startup. The startup class must contain a method named Configure with the signature shown here. Inside this method, use the IBuilder interface to configure the application.

The UseWelcomePage methods adds a middleware component that just displays a welcome page. The welcome page is useful for diagnostic purposes, to make sure your project is configured and running correctly.

To start the application, open a command prompt and type the following commands:

kpm restore
k web

The kpm restore command resolves the dependencies listed in the project.json file, and downloads the necessary NuGet packages. The k web command starts the HTTP listener.
Notice there is no explicit build step. The k web command compiles the code on the fly. After you install the NuGet packages, you can make changes to the code and run k web again, without running kpm restore.

Next, launch a browser and navigate to http://localhost:5001. You should see the welcome page.

The web command is defined in the project.json file:

  "commands": {
    "web": "Microsoft.AspNet.Hosting server=Microsoft.AspNet.Server.WebListener server.urls=http://localhost:5001"
  },

This command starts the hosting environment and listens on the specified localhost address. You can edit the project.json file to use a different port number.

Serving Static Files

The welcome page is not too interesting, so lets’s enable the app to serve static files. Add the following entry to the “dependencies” section of the project.json file:

"Microsoft.AspNet.StaticFiles": "0.1-alpha-build-0402"

Modify the Startup class as follows.

using Microsoft.AspNet.Builder;
using Microsoft.AspNet.StaticFiles;

public class Startup
{
    public void Configure(IBuilder app)
    {
        app.UseStaticFiles();
    }
}

Getting Started with MVC 6

In the rest of this overview, we’ll explore some of the features of MVC 6. To enable MVC, modify the Startup class as follows.

using Microsoft.AspNet.Routing;
using Microsoft.AspNet.Builder;
using Microsoft.Framework.DependencyInjection;

public class Startup
{
    public void Configure(IBuilder app)
    {
        app.UseServices(services =>
        {
            services.AddMvc();
        });

        app.UseMvc(routes =>
        {
            routes.MapRoute(
                name: "Default",
                template: "{controller}/{action}/{id?}",
                defaults: new { controller = "Home", action = "Index" });
        });

    }
}

This code enables MVC and defines a route. If you’ve used earlier versions of MVC, the MapRoute method should look familiar. For comparison, here are the same routes defined in MVC 5 and MVC 6:

// MVC 5 route
routes.MapRoute(
    name: "Default",
    url: "{controller}/{action}/{id}",
    defaults: new { controller = "Home", action = "Index",
        id = UrlParameter.Optional }
);

// MVC 6 route
routes.MapRoute(
    name: "Default",
    template: "{controller}/{action}/{id?}",
    defaults: new { controller = "Home", action = "Index" }
);

The ‘?’ character in the template means the {id} segment is optional.

Next, add a controller class. The following controller defines a single action named Index that returns a view.

using Microsoft.AspNet.Mvc;

public class HomeController : Controller
{
    public ActionResult Index()
    {
        return View();
    }
}

Except for the namespace, this code would compile in MVC 5.

Now add a view. Create a file named ./Views/Home/index.cshtml and paste in the following code.

@{
  var message = "Hello World";
}

<!DOCTYPE html>

<html lang="en">
<head>
  <meta charset="utf-8" />
  <title>Index Page</title>
</head>
<body>
  <h1>@message</h1>
  <p>Index page</p>
</body>
</html>

I included a @message variable just to show that this is a Razor file and not just static HTML.

Here is the file structure for the project:

.\HomeController.cs
.\project.json
.\Startup.cs
.\Views\Home\Index.cshtml

Run the app by using the k web command, and then navigate to http://localhost:5001. You should see the HTML that is rendered by the Index view.

View Models

You can pass a model to the view. Let’s add a model class:

public class MessageModel
{
    public string Message { get; set; }
}

Modify the action by passing an instance of MessageModel to the View method:

public class HomeController : Controller
{
    public ActionResult Index()
    {
        var model = new MessageModel { Message = "Hello ASP.NET" };
        return View(model);
    }
}

Update index.cshtml to refer to the model.

<!DOCTYPE html>

<html lang="en">
<head>
  <meta charset="utf-8" />
  <title>Hello World Page</title>
</head>
<body>
  <h1>@Model.Message</h1>
</body>
</html>

Now when you run the app, “Hello ASP.NET” is rendered inside the H1 tag.

Creating Web APIs and REST-Style Actions

If the route template does not include {action}, the framework uses the HTTP verb to select the action name. This style of routing is similar to convention-based routing in the current version of ASP.NET Web API, and is useful for REST-style APIs.

Here is an example of a route template without an {action} variable.

app.UseMvc(routes =&gt;
{
    routes.MapRoute("ApiRoute", "{controller}/{id?}");
});

Using this route template, the action name maps to the HTTP verb in the request. For example, a GET request will invoke a method named Get, a PUT request will invoke a method named Put, and so forth. The {controller} variable still maps to the controller name.

The following controller uses this style of routing.

using Microsoft.AspNet.Mvc;

public class ValuesController : Controller
{
    // GET /values
    public string Get()
    {
        return "Values";
    }

    // GET /values/1
    public string Get(int id)
    {
        return "Value " + id.ToString();
    }

    // POST /values
    public ActionResult Post()
    {
        return new HttpStatusCodeResult(201);
    }
}

The following table shows the web API that is defined by ValuesController.

Request Method URI Path Controller Action
GET /values Get
GET /values/1 Get(id)
POST /values Post

The two Get actions both return strings. In that case, the framework writes the string into the body of the HTTP response, and sets the Content-Type header to “text/plain”. For example, if you send a GET request to /values/1, the response will look similar to the following.

HTTP/1.1 200 OK
Content-Type: text/plain
Server: Microsoft-HTTPAPI/2.0
Date: Wed, 30 Apr 2014 00:16:38 GMT
Content-Length: 7

Value 1

The Post action returns an HttpStatusCodeResult. The framework translates this into an HTTP status code.

HTTP/1.1 201 Created
Content-Length: 0
Server: Microsoft-HTTPAPI/2.0
Date: Wed, 30 Apr 2014 00:18:58 GMT

If you are familiar with ASP.NET Web API, you may have noticed that ValuesController derives from Controller, not ApiController. That’s because vNext does not have a separate controller class for web APIs.

In the current ASP.NET framework, MVC 5 and Web API 2 use completely different classes and namespaces. That means a controller is either an MVC controller or a Web API controller. Web API controllers use separate routes, and they can’t use MVC filters or MVC model binders.

One goal of ASP.NET vNext is to merge MVC and Web API into a single framework, which shares a single pipeline and uses the same routing, action selection, filters, model binding, and so forth. The result will be a more consistent programming model, and code that is more re-usable.

Returning JSON

To serialize an object into JSON format, call Controller.Json. This method returns a JsonResult, which is an action result that serializes an object to JSON format. For example, let’s add a model class named Movie.

public class Movie
{
    public string Title { get; set; }
    public int Year { get; set; }
    public string Genre { get; set; }
}

Here is a controller that returns a list of movies in JSON format.

using Microsoft.AspNet.Mvc;

public class MoviesController : Controller
{
    public ActionResult Get()
    {
        var movie = new Movie
        {
            Title = "Maximum Payback", Year = 1990, Genre = "Action"
        };
        return Json(movie);
    }
}

The response from the Get action will look similar to the following.

HTTP/1.1 200 OK
Content-Type: application/json
Server: Microsoft-HTTPAPI/2.0
Date: Fri, 02 May 2014 20:39:25 GMT
Content-Length: 120

[{"Title":"Maximum Payback","Year":1990,"Genre":"Action"},{"Title":"Fatal Vengeance 2","Year":2012,"Genre":"Action"}]

Note: The preview release does not support content negotiation yet.

Areas

Areas are a way to group controllers, models, and views. In previous versions of MVC, you register areas by calling AreaRegistration.RegisterAllAreas. Area controllers are placed in a special Areas folder.

In MVC 6, you create a route template with an {area} parameter, and then decorate area controllers with the [Area] attribute. The following code defines an area route.

app.UseMvc(routes =&gt;
{
    routes.MapRoute(
        name: "AreasRoute",
        template: "{area}/{controller}/{action}");

    routes.MapRoute(
        name: "Default",
        template: "{controller}/{action}/{id?}",
        defaults: new { controller = "Home", action = "Index" });
});

Given these routes, you could define two Home controllers, as follows:

namespace MyApp.Controllers
{
    public class HomeController : Controller
    {
        // Home/Index
        public ActionResult Index()
        {
            return View();
        }
    }
}
namespace MyApp.Areas.Controllers
{
    [Area("Books")]
    public class HomeController : Controller
    {
        // Books/Home/Index
        public ActionResult Index()
        {
            return View();
        }
    }
}

The second controller is assigned to the Books area.

URI Controller
/Home/Index MyApp.Controllers.HomeController
/Books/Home/Index MyApp.Areas.Controllers.HomeController

Views for an area go into a folder named “Areas/{area name}/Views/{controller}”. So in this example, the view for the Books/Home/Index action would go in a file named “Areas\Books\Views\Home\index.cshtml”.

Previously, the Web API framework did not support areas. Because MVC 6 merges the two frameworks, you can now organize web API-style controllers into areas.

View Components and Child Views

View components are similar to child actions in previous versions of MVC. They allow a view to invoke an action and render the result within the view. The following code shows a simple view component that writes a text string.

[ViewComponent(Name = "MyViewComponent")]
public class SimpleViewComponent : ViewComponent
{
    public IViewComponentResult Invoke(int num)
    {
        var message = String.Format("The secret code is: {0}", num);
        return Result.Content(message);
    }
}

To include this view component in a view, call Html.Component.

<html lang="en">
<head>
  <meta charset="utf-8" />
  <title>Index Page</title>
</head>
<body>
  <p>@Component.Invoke("MyViewComponent", 42)</p>
</body>
</html>

When the view is rendered, the p tag will contain the string “The secret code is 42”. Notice that you can pass parameters to the view component’s Invoke method.

POCO Controllers

In MVC 6, controllers do not need to derive from Microsoft.AspNet.Mvc.Controller. You can write a controller as a simple class or “POCO” (plain old CLR object).
Here is an example.

public class HomeController
{
    // Helpers can be dependency injected into the controller
    public HomeController(IActionResultHelper resultHelper)
    {
        Result = resultHelper;
    }

    private IActionResultHelper Result { get; set; }

    public ActionResult Index()
    {
        return Result.Json(new { message = "Poco controllers!" });
    }
}

IActionResultHelper is a helper for creating action results. Notice that the IActionResultHelper instance is injected into the controller via the constructor. The framework provides a default IActionResultHelper implementation, and automatically injects it. You could also provide your own implementation of IActionResultHelper.

Previously, I showed a controller calls Controller.Json to return JSON data. That method is really just syntactic sugar for calling IActionResultHelper.Json.

The Controller class also gives you convenient access to the HTTP request context, the current principal (IPrincipal), a view bag, and other useful properties. So the Controller class is certainly useful, but it’s not required. For a light-weight controller, you might prefer a POCO controller.

Planning Role Management in ASP.Net

When planning role management, follow these best practices:
1> Use Windows authentication for intranet applications when users have Active Directory domain accounts. This provides single sign-on for users and centralizes account management. If you use Windows authentication, ASP.Net uses roles to represent group memberships.
2> If you must create accounts for users separate from their Active Directory domain accounts, work with systems administrators to include the application’s role management in their account management process. For example, when a user leaves the organization, systems administrators will need to remove both the user’s Active Directory domain account and the application account.
3> Never assign privileges to an individual user. Instead, add users to roles, and assign privileges to those roles. If an employee leaves the organization, you only need to remove the user from the role rather than modifying how privileges are assigned.
4> Create separate roles for different management tasks. For example, instead of creating roles for just users and administrators of a blog application, create separate roles for readers, writers, editors, content approvers, and website managers. Even though it might require you to add users to multiple roles, having more granular roles simplifies delegating tasks if more flexibility is required in the future.
5> Always derive new security classes from existing .NET classes. Microsoft has carefully reviewed and tested the security components of the .NET framework. This does not mean the .NET framework does not contain security weaknesses; all code does. However, the .NET framework’s extensive review and testing helps to make them more secure than classes written by individual developers.

ASP.Net web services (ASMX) vs WCF web services

The following are the few things which distinguish ASMX services to WCF webservices:
–WCF web services provide many bindings
–WCF web services are written to implement contracts defined by interfaces.
–For ASMX web services, you add attributes to the methods. For WCF web services, you add attributes to the interfaces.
–ASMX web services must be hosted in IIS, but WCF web services can ei

.Net common questions

Here are some common questions on .Net which can be asked in interviews:

Describe the difference between a Thread and a Process?
An application consists of one or more processes. A process, in the simplest terms, is an executing program. One or more
threads run in the context of the process. A thread is the basic unit to which the operating system allocates processor
time. A thread can execute any part of the process code, incluging parts currently being executed by another thread.

What is a Windows Service and how does its lifecycle differ from a “standard” EXE?
Windows service allows you to create long-running executable applications that run in their own windows sessions. These
services can be managed to start at the boot time or can be controlled manually. The windows service do not have any UI to show
to the user.
Windows service lifetime:
For the service to run, it need to be installed. With the installation, it will load the service into the Service control manager
. Once the service is installed, one can start from the Service Control Manager or from code “start”. The service will run until someone
stops it or the system is shutdown. The service can in any one of these status running, paused or stopped. One can write code to
handle in these statuses.

Standard ‘Exe’ need to be started manually everytime you log in. Standard ‘Exe’ can have UI for the user.

What is the difference between an EXE and a DLL?
EXE is an extension used for executable files while DLL is the extension for a dynamic link library.
An EXE file can be run independently while a DLL is used by other applications
An EXE file defines an entry point while a DLL does not
A DLL file can be reused by other applications while an exe cannot.
A dll would share the same process and memory space of the calling application while an exe creates its separate process and memory space.

What is strong-typing versus weak-typing?
Strong typing means that once assigned a value of a particular kind, objects objey strict rules about how they can interact with other objects of vaious types.
Weak typing means that such rules are more relaxed.
Python is considered strongly typed while PHP is considered weak-typing.
c# is strong types and javascript is weak typed.

still to come…

CSS for Disabled anchor tag on asp.net

In the asp.net when the link was disabled it used to apply the disabled properties for the anchor tags. With the 4.0 .Net framework, the colors won’t apply automatically. They introduced a new property for all controls DisabledCssClass which is a string property to set/get the disabled css class. This property is applied to all the controls.
This property can be used to change the name that is rendered for the DisabledCssClass property of individual Web controls. By default, this property returns “aspNetDisabled“.
When SupportsDisabledAttribute is overridden in a derived class to return false, the value of the DisabledCssClass property is rendered as the value of the class attribute of the HTML element for the control. In that case, if there is a value in the CssClass property, both CSS classes will be applied to the rendered HTML element. The class attribute will consist of the value of the DisabledCssClass property followed by the value of the CssClass property, separated by a space.
This property is static, which means that you can set it only for the WebControl class. Whatever value you set it to is used for all controls in a Web application. You cannot specify different values for individual controls.
If you want to set a new class for all the controls all over the application, you can set a new class in the application_start event in global.asax

void Application_Start(object sender, EventArgs e)
{
webcontrol.DisabledCssClass = somecssclass;
}

If you want to set the DisabledCssClass for an anchor tag, you can do that in the stylesheet like

a.aspNetDisabled
{
color:000FFF#;
}

This set of property is applied to anchor tag without affecting any other controls.