Integrating ASP.NET Web Forms and ASP.NET MVC

With ASP.NET MVC being a mature platform, many Web Forms developers are wondering whether or not they should move to MVC or are thinking about integrating MVC into their existing Web Forms projects. Web Forms has caught up to MVC in many respects. For example, Web Forms V4+ supports routing, and the controls render less HTML than ever before. ViewState went on a diet and is considerably smaller. In the past some have turned to MVC to address these concerns, but no longer is this the case.

If you’re interested in more content about migrating or integrating Web Forms and MVC, see my WintellectNOW video, “Migrating from Web Forms to MVC”. It covers the many concerns developers face when making the decision about whether or not to migrate to a new technology (and whether or not you should at all). In the meantime, below are some practical tips and techniques required when integrating the two technologies.

MVC Integration: Setup, References, and Configuration

You can install the ASP.NET MVC 4 NuGet package that includes all the resources that you need to use MVC such as references, web.config changes, etc… Once you’ve installed the NuGet package there is little you need to do to use MVC except create folders named “Models”, “Views”, and “Controllers” (assuming you are keeping all these in the same project).

image_thumb3

The NuGet Package adds in several changes to the web.config file as well as references to the project that are worth examining. The web.config sample below shows these references:

Location: <configuration><appSettings>

Configure the ASP.NET Web Pages rendering engine settings in the <appSettings> element.

<appSettings>
  <add key=webpages:Version value=2.0.0.0 />
  <add key=webpages:Enabled value=false />
  <add key=PreserveLoginUrl value=true />
  <add key=ClientValidationEnabled value=true />
  <add key=UnobtrusiveJavaScriptEnabled value=true />
</appSettings>

Location: <configuration><system.web>

This code adds various names
paces to the project’s compilation as well as parser filter and base types, which are settings that determine how views render. The namespace references below are the automatic imports to namespaces for use in views only. You must continue use the using keyword in C# code. The general namespace inclusion is in the previous example.

<pages pageParserFilterType=System.Web.Mvc.ViewTypeParserFilter, System.Web.Mvc,
       Version=2.0.0.0, Culture=neutral, PublicKeyToken=31BF3856AD364E35
       pageBaseType=System.Web.Mvc.ViewPage, System.Web.Mvc,
       Version=2.0.0.0, Culture=neutral, PublicKeyToken=31BF3856AD364E35
       userControlBaseType=System.Web.Mvc.ViewUserControl, System.Web.Mvc,
       Version=2.0.0.0, Culture=neutral, PublicKeyToken=31BF3856AD364E35>
  <namespaces>
    <add namespace=System.Web.Optimization />
    <add namespace=System.Web.Helpers />
    <add namespace=System.Web.Mvc />
    <add namespace=System.Web.Mvc.Ajax />
    <add namespace=System.Web.Mvc.Html />
    <add namespace=System.Web.Optimization />
    <add namespace=System.Web.Routing />
    <add namespace=System.Web.WebPages />
    <add namespace=System.Web.WebPages.Html />
  </namespaces>
  <controls>
    <add assembly=Microsoft.AspNet.Web.Optimization.WebForms
     namespace=Microsoft.AspNet.Web.Optimization.WebForms
     tagPrefix=webopt />
  </controls>
</pages>

Location: <configuration><system.webServer><handlers>

These are the ASP.NET runtime HTTP handlers. They are what determines which .dlls service which type of requests at a low level. As demonstrated, these handlers are looking to interact with HTTP via verbs.

<handlers>
  <remove name=ExtensionlessUrlHandler-ISAPI-4.0_32bit />
  <remove name=ExtensionlessUrlHandler-ISAPI-4.0_64bit />
  <remove name=ExtensionlessUrlHandler-Integrated-4.0 />
  <add name=ExtensionlessUrlHandler-ISAPI-4.0_32bit path=*.
       verb=GET,HEAD,POST,DEBUG,PUT,DELETE,PATCH,OPTIONS modules=IsapiModule
       scriptProcessor=%windir%Microsoft.NETFrameworkv4.0.30319aspnet_isapi.dll
       preCondition=classicMode,runtimeVersionv4.0,bitness32 responseBufferLimit=0 />
  <add name=ExtensionlessUrlHandler-ISAPI-4.0_64bit path=*.
       verb=GET,HEAD,POST,DEBUG,PUT,DELETE,PATCH,OPTIONS modules=IsapiModule
       scriptProcessor=%windir%Microsoft.NETFramework64v4.0.30319aspnet_isapi.dll
       preCondition=classicMode,runtimeVersionv4.0,bitness64 responseBufferLimit=0 />
  <add name=ExtensionlessUrlHandler-Integrated-4.0 path=*.
       verb=GET,HEAD,POST,DEBUG,PUT,DELETE,PATCH,OPTIONS type=System.Web.Handlers.TransferRequestHandler
       preCondition=integratedMode,runtimeVersionv4.0 />
</handlers>

Location: <configuration><runtime><assemblyBinding>

Of course if you’re dealing with differing versions of .NET for any type project, you must change assembly bindings. Assembly bindings declare which versions of which libraries to reference in the project. VS will compile against the new redirected binding than the default when you use the settings below:

<dependentAssembly>
  <assemblyIdentity name=System.Web.Helpers publicKeyToken=31bf3856ad364e35 />
  <bindingRedirect oldVersion=1.0.0.0-2.0.0.0 newVersion=2.0.0.0 />
</dependentAssembly>
<dependentAssembly>
  <assemblyIdentity name=System.Web.Mvc publicKeyToken=31bf3856ad364e35 />
  <bindingRedirect oldVersion=1.0.0.0-4.0.0.0 newVersion=4.0.0.0 />
</dependentAssembly>
<dependentAssembly>
  <assemblyIdentity name=System.Web.WebPages publicKeyToken=31bf3856ad364e35 />
  <bindingRedirect oldVersion=1.0.0.0-2.0.0.0 newVersion=2.0.0.0 />
</dependentAssembly>

After configuring the project to incorporate MVC, you’ll need to setup routing.

Controllers and Routing

Routing is an essential component of MVC development, and MVC cannot work without it. In Web Forms V4 and later, routing is baked right in. What you’ll need to do to ensure the proper routes are set is to create a static RouteConfig class, preferably in a file (e.g., RouteConfig.cs) inside the App_Start special folder. After that, add in the code below to assign a generic route.

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

Of course, the RouteConfig class won’t instantiate itself. That means you must call its RegisterRoutes function (also static) from the Global.asax.cs file like so:

void Application_Start(object sender, EventArgs e)
{
    RouteConfig.RegisterRoutes(RouteTable.Routes);
}

The last thing to do is use MVC conventions to create the appropriate folders for Models, Views, and Controllers, if you haven’t already. Otherwise, structure your project as you would for use with the MVC pattern, perhaps moving models to their own class library or service layer.

Considerations when integrating Web Forms and MVC

DataSets/DataReaders & Models:

A lot of data is accessed by Web Forms via declarative tags like the <asp:SqlDataSource>, as well as volumes of DataSets and DataReaders in the code behind files. You’ll need to find a strategy for converting these to models, i.e., classes. Some Web Forms projects contain POCOs for models and those often port over quickly. By convention (assuming a single project), model files live in the <ProjectRoot>Models folder and model classes in the <Project>.Models namespace.

ASPX & Views:

ASP.NET MVC ships with two view engines: Web Forms (ASPX) and Razor. The ASPX view engine continues on using the classic <%# %> syntax for code delimiters, while Razor uses only the @ symbol (or @{}) as a way to denote the start of of code. Razor uses a new parsing engine first introduced in ASP.NET Web Pages that produces clean and concise HTML output. However, if you have a team strong in Web Forms they may want to continue using Web Forms syntax. The difference worth mentioning is that the ASPX view engine uses the traditional Web Forms rendering under the hood so technically it builds a control tree and renders it. You just can’t access the elements in MVC views like you can in a Web Forms page by referring to a control as an object in the code behind. This makes Razor much faster as there is no tree to render. In  views, code renders inline, or in placeholders, rather than from scripted code in a code behind. This is a drastic enough difference that you’ll probably need to completely rewrite many Web Forms as MVC views, as opposed to simply reusing pages in MVC. Of course, redoing all pages as views all at once is often not an option because of time and budget, but you can move them one by one.

Any would be controls in MVC become Html helpers. Html Helpers are the cornerstone of ASP.NET MVC views. Like controls, the Html Helpers render chunks of browser friendly output, but helpers emit the least amount of code as possible and in the least obtrusive way. Helpers also accept and render data from the model. This means if you have 3rd party controls, you might want to migrate these pages last or weigh the option of leaving them as Web Forms. This, of course, depends upon the cost-benefit of the developer’s time to build a control vs. buying a new version of one, if one is available. Most popular 3rd party vendors are up to date.

Code Behind Files & Controllers:

It is not uncommon to see a Web Forms code behind file with 5,000+ lines of code. That’s a lot of code for one single Page object. It also makes the page object a Swiss army knife of sorts as Page objects deal with building the UI and doing all sorts of other things. Many developers add CRUD operations directly in the code behind. This page of all trades ends up doing all the chores and this means more complex code and code that is tightly coupled.

MVC leans toward a concept called Separation of Concerns in which each part of the MVC pattern maps to a concern. M for models or data and CRUD operations. V for views or UI. C for controllers or operational code. All the layers are nicely separated. If your Web Forms code is getting a bit unruly or spaghetti-like then MVC could address and fix some of your maintenance issues by breaking out components into manageable units, or concerns.

Controllers of course make the calls to Web services to retrieve JSON or XML data or directly to the database, a repository, or any number of options. Controllers also do the work of determining how HTTP requests are handled. This responsibility falls to the code behind in Web Forms.

ASP.NET Core:

Since it’s all ASP.NET, you get to share core features such as sessions, caching, globalization, Forms authentication between Web Forms and MVC.

Summary

Fortunately assets like images, CSS, and custom JavaScript are all reusable between Web Forms and MVC projects. Just keep the ID and NAME attributes the same (which you want anyway for consistency). As you can see, both technologies are ASP.NET so they can live harmoniously and even compliment each other.

As you can see, with just a few modifications to a Web Forms project and you can start adding MVC components. You can run both Web Forms and MVC or work toward doing a complete migration.

JavaScript Strict Mode Explained

JavaScript is everywhere. It’s run in web sites, as utilities on many operating systems, and in any host, like IE, Firefox, or Chrome and it’s a first class citizen in Windows 8 Metro style app development. Since JavaScript has been around for a long time, it still has a lot of baggage from when it was immature. Because of this, Strict Mode has become a feature in ECMAScript 5, or ES5 (JavaScript).

What is Strict Mode and why use it?

Because Strict Mode is ECMAScript, it is a standard, and a best practice, and highly recommended that you use it. In the future, Strict Mode will be your only choice, which is certainly for the best. Strict Mode offers up these enhancements to the JavaScript language:

  • JavaScript throws errors if you try to use deprecated language elements
  • Variable declaration is mandatory
  • Disallows duplicate property and parameter names
  • The eval() method is safer to use, but still considered evil in some cases.
  • Deprecates the with statement
  • JavaScript throws errors if you try to assign a value to a read only property
  • Decreases the global namespace pollution

Most ES5 compliant JavaScript runtimes support Strict Mode, and you can get full details at this in-depth article on Strict Mode at MSDN.

Where can I use Strict Mode?

You can use strict mode in any JavaScript host or engine that supports ES5 standards, and specifically, Strict Mode. Check out this comprehensive ES5 Compat Table on Github to see if your browser supports strict. You will see a lot of green lights, so there is wide support across browsers. This means if you are a web developer you can start using Strict Mode today.

If you are a Windows 8 Metro style apps HTML/JS developer, Strict Mode is automatically added to the project templates in Visual Studio 11 as WinJS supports Strict Mode.

Enabling Strict Mode

Applying Strict Mode is very easy to do. Just add the “use strict” directive to your code (it’s a string literal so include the quotes). The physical location of the strict directive determines the scope of Strict Mode. Below is a table showing the relationship between Strict Mode and scope. This means you can turn Strict Mode on and off granularly in code.

Code location Scope
Beginning of any .js file Global
Beginning of the script inside a <script> element. <script> element
Preceding function block
First line in function block
Function

As you can see, Strict Mode is flexible but try to keep Strict Mode out of a global setting where possible when dealing with Web pages (HTML, ASP.NET, PHP, etc…). If other scripts include your script using Strict Mode, then Strict Mode could apply to the included scripts and that can create problems. However, you can get the same effect as global Strict mode by wrapping your code like so:

$(function () {
    “use strict”;
    function strictFoo() {
        alert(“I am in strict mode”);
    }
    function strictFoo2() {
        alert(“Me too!”);
    }
});

This creates a block around both functions and Strict Mode appears global to to the all code that exists in that block, essentially making strict container for that code. 

Summary

Strict Mode is great because it catches common programming ID10T errors. These are the kind of errors everyone makes, regardless of experience, and often because of experience. It’s very easy, especially when moving from a compiled language, to miss some of the finer nuances of JavaScript. Strict Mode helps smooth out those JS language kinks.

Create mobile site layouts with CSS Media Queries

Web sites and apps need to deal with the challenge of serving content to a multitude of browsers and devices. People access web sites and apps via tablets and mobile phones more than ever before, and smart phone usage numbers are growing exponentially. In some populations, mobile Web traffic is higher than traffic from desktops. Technology nowadays means devices and machines range in size from quite small to quite big, and as a result, you the developer must format the content appropriately for each device type. You can accomplish this task by using CSS Media Queries, as they are the best foundation of a responsive UI.

What is a CSS Media Query?

In the past, in order to serve browser or device specific content, we would write code that determines which style sheet to use based on feature detection (or UA detection on older Web sites). Now, instead of having to write code, we can use declarative CSS Media Queries to apply rules to an HTML page based on the requesting device’s characteristics. CSS Media Queries are a way to apply different styles when the requesting browser or device matches the conditions within the media query. With media queries you can target various screen sizes, orientations, and form factors including TV and print, and serve tailored content to them. For example, the media queries below apply a different layout to the tablet sized, landscape screen (768 x 1366 ), vs. the phone sized, portrait screen (320 x 480):

@media screen and (min-width: 768px) and (orientation: landscape)

{
    /* CSS layout for screens with minimum 800px width, landscape */

} @media screen and (max-width: 320px) and (orientation: portrait)

{
    /* CSS layout for screens with maximum 320px width, portrait */
}

While multiple media queries can exist side by side in a single .css file (like the example above), maintenance can be easier if you create one .css file for each type of device you want to support. Doing so allows you to swap style sheets based on the media query defined in the media attribute of the <link> tag.

<link rel=”stylesheet” type=”text/css” href=”smartphones.css” media=”only screen and (max-device-width: 320px)” /> <link rel=”stylesheet” type=”text/css” href=”tablets.css” media

="screen and (min-device-width: 800px)" />

Effectively, media queries rid you of the long lines of “if then” statements otherwise required as conditional logic to figure which style sheet to use for which occasion. You no longer need to resort to using JavaScript to swap style sheets by querying user agents, media types or common device form factors.

Design a page layout with CSS Media Queries

Layouts that fit traditional landscape screens work horribly on smart phones, and thus the need for a responsive layout. A responsive layout is fluid and adaptable, and needs flexible elements such as grids and images that can automatically resize based on the form factor of the requesting device. In addition to resizing elements, you must adapt the page to remove content or unnecessary navigation, because space is at such a premium on small devices.

CSS Media Queries are the foundation of responsive layouts that work across devices. Let’s start with an example of a simple web page with a two column layout in which there is a container <div> and two child <div> tags that render the columns. This layout is for desktop browsers, and later we’ll modify it to run on a phone.

#wrapper 

{ margin:0 auto; height:768px; } #sidebar { background-color:#2885c9; width:24%; height:600px; float:left; } #content { background-color:#229731; width:75%; height:600px; float:right

;
}

<!DOCTYPE html> <html xmlns=”http://www.w3.org/1999/xhtml”&gt; <head> <title>CSS Media Queries</title> <link href=”default.css” rel=”stylesheet” /> </head> <body> <div id=”wrapper”> <div id=”sidebar”><span>Side bar</span></div> <div id=”content”><span>Content goes here.</span></div> </div> </body> </html>

The code above looks like this in IE 10, a desktop browser. There is a column to the left (side bar) and one on the right (content).

 

image_thumb3_2

Of course, this layout just won’t work in a small, portrait, screen. Most side bars are for navigation, that when mobilized is painful to use in such a small form. Repositioning the elements so that the side bar is on top of the content is a much better layout for smart phones, because of the change in orientation. We can do this by creating a media query and modifying the CSS to fit smart phone dimensions. Below is a media query definition containing the same three selectors in the previous sample, but modified for a smart phone layout. What was the leftmost column (the side bar) is now positioned at row #1, and its adjacent content area is now positioned at row #2. As you might expect, the sizes of the elements are smaller than in the desktop version.

@media screen and (max-width: 320px) and (orientation: portrait) { #wrapper { width:320px; height:480px; margin: 0 0 0 5px; } #sidebar { width:320px; height:90px; float:left; margin: 0 0 5px 0; } #content { width:320px; height:380px; float:left

;
    }
}

 

image_thumb2_2SNAGHTML103a6a17_thumb1_2

The media query works great in IE10 desktop when resized to smart phone dimensions (left side, above image). However, in some phones or emulators, the above media query does not work (right side, above image). This is because we are missing a key component in mobilizing content – the <viewport> meta.

Mobilizing sites with the viewport meta

When mobile devices receive content formatted for the desktop or larger sized browsers, their default action is to zoom out to show all the content. The phone browser tries to show the page as a desktop browser does but condensed into its tiny, portrait, view. They do this for backward compatibility of the many non-mobilized sites that phones otherwise render incorrectly and break. We can change this behavior and tell phones to optimize their default zoom for mobile by using the viewport meta element. The viewport meta instructs mobile devices to resize the content to fit on their screen or to a certain scale based on the tag’s attribute values. Below is an all-purpose viewport that resizes content to fit the device:

<meta name=“viewport” content=“width=device-width”/>

If you aren’t sure what attributes to use, use the above as the default, as it renders the page to fit the device. Now because the phone will render the content correctly, and the output looks like the following:

SNAGHTML9843bc_thumb1_thumb

Notice the browser has applied the media query this time. This is because the phone’s browser took a cue from the viewport and rendered the page like a mobile browser rather than a desktop browser.

Summary

As you can see, CSS Media Queries are the best way to deliver perfectly fitted content to any device, with less maintenance hassles. Media queries aren’t just for the Web either – you can write Windows Store apps in HTML/CSS/JavaScript and use media queries for Windows 8 features like Snap-View. If you are working cross platform, don’t worry about support as CSS Media Queries have a wide adoption across desktop and mobile browsers.

Lastly, if you would like to go mobile but must support the older-than-dirt browsers like IE8 and below then check out Respond.js. Respond is a polyfill for CSS Media Queries (a mechanism for backwards compatibility), enabling their use in old or unpopular browsers.

Write Object-Oriented JavaScript with TypeScript

TypeScript, Microsoft’s new language, is proving to be a popular choice amongst ASP.NET and Windows developers. Of course, those coming from the Microsoft stack are used to working with Object Oriented languages, except with significantly differing syntaxes. TypeScript brings familiar OOP constructs to JavaScript. TypeScript is not a new language as it is a superset of JavaScript that generates plain JavaScript. There are four main principles to Object Oriented Programming: Encapsulation, Inheritance, Abstraction, and Polymorphism. TypeScript can implement all four of them with its smaller and cleaner syntax.

For a primer on TypeScript, read TypeScript, A New Language For .NET & JavaScript Developers.

Encapsulation

Encapsulation is a key part of Object Oriented Programming that is a way to structure code so that a certain block of code has specific access points for external code. The term for this is “visibility” or “accessibility”. Visibility defines what code from one method, property, or class can call code in another method, property, or class. In other words, if we were to interact with a real world object like a car, we do so by using only certain parts of the car that are there for that purpose. These components of the car communicate to parts inside the car that perform the actions on our behalf. In the case of a car, these external parts are the pedals, steering, and dashboard controls, while the internal ones are in the engine. This means we don’t need to know what goes on under the car’s hood to make the car go, stop, or turn, all we need to do is interact with the correct component, called an interface. (i.e., the pedals, steering, dashboard controls). To enforce encapsulation in many languages, we use methods and properties. Both are blocks of code, although they differ mostly in syntax rather than conceptually. Behind each method or property is logic that often hides private data and performs complex tasks. The calling code shouldn’t and doesn’t need to know about those things.

In TypeScript, we enforce encapsulation with methods and properties that only allow access to data that we control. The Withdraw method below does that by doing the calculation and updating the class level _balance field. The Balance property then returns the private _balance field to the calling code.

Withdraw(amount: number): boolean
{
    if (this._balance > amount)
    {
        this._balance -= amount
        return true;
    }
    return false;
}

private _balance: number;
get Balance(): number {
    return this._balance;
}

This encapsulates the account’s balance as business logic and validation code can run and access the private variables to formulate something to return to the client. In turn, the client never needs to know what goes on behind the scenes, just how to interact with the object. TypeScript’s syntax is similar to that of a statically typed language like C#, by using constructs like setters and getters.

Inheritance

It’s quite easy to create an object model and inheritance chain with TypeScript. Just start with the familiar class keyword to create classes. The extends keyword causes the child class to inherit from the denoted base class. For example, we can build out a very simplistic SavingsAccount and CheckingAccount classes that derive from a BankAccount class, like so:

module Bank {
    class BankAccount { }

    class SavingsAccount extends B
ankAccount { }

    class CheckingAccount extends BankAccount { }
}

The two above TypeScript samples generate the JavaScript below. It’s very clear in TypeScript sample above that inheritance is happening, but not as clear in straight up JavaScript sample below. Sure, you could write this yourself, but as you can see, TypeScript generates the code you’re supposed to write, but without all the typing involved. There are only three lines of code needed for Bank class, but thirty for JavaScript. That’s a difference of ten times as much.

var __extends = this.__extends || function (d, b) {
    for (var p in b) if (b.hasOwnProperty(p)) d[p] = b[p];
    function __() { this.constructor = d; }
    __.prototype = b.prototype;
    d.prototype = new __();
};
var Bank;
(function (Bank) {
    var BankAccount = (function () {
        function BankAccount() {
        }
        return BankAccount;
    })();

    var SavingsAccount = (function (_super) {
        __extends(SavingsAccount, _super);
        function SavingsAccount() {
            _super.apply(this, arguments);
        }
        return SavingsAccount;
    })(BankAccount);

    var CheckingAccount = (function (_super) {
        __extends(CheckingAccount, _super);
        function CheckingAccount() {
            _super.apply(this, arguments);
        }
        return CheckingAccount;
    })(BankAccount);
})(Bank || (Bank = {}));

TypeScript classes make it easy to map properties to JSON or XML data, common in web sites and apps. Looking at the above sample, you can see that it does adhere to the module pattern. TypeScript supports single inheritance.

Abstraction

There is no formal mechanism for creating an abstract class in TypeScript, although a request to implement abstraction in TypeScript has been issued. Not to worry, for now we can use interfaces as a way to abstract class members. For example, a bank might have an Fee interface
(their favorite one!) or an Interest interface that all account objects must implement. The Fee interface has members such as ChargeFee and the Interest interface contains one named CalculateInterest. When classes implement these interfaces, they must implement all of the members of the interface, as interfaces serve as digital contracts that classes can adhere to.

You can use the implements keyword to implement an interface in TypeScript, as shown here:

export module Bank
{
    export interface Fee { ChargeFee(amount: number); }

    export class BankAccount implements Fee {
        ChargeFee(amount: number) { }
    }
}

It’s syntactically like the extends keyword.

Polymorphism

TypeScript enables polymorphism via method overrides as you can see in the example below. The Withdraw and Deposit methods of the CheckingAccount and SavingsAccount classes derive from the parent BankAccount class. In the child classes, we can override these methods and add our own business logic customizations, such as waving a fee if the balance is more than a specified amount.

class SavingsAccount extends BankAccount
{
    ChargeFee(amount: number)
    {
        if (this.Balance > 1000) { amount = 0; }
        else { amount += 1.00; } 
         
        this.Balance =+ amount;
    }
}

In this case, we overrided the ChargeFee that was originally part of the Fee interface. Polymorphism is an essential characteristic of OO programming, as code would be quite redundant without it.

Summary

As you can see, TypeScript enables all four of the primary object oriented programming techniques with easy to use keywords and syntax. TypeScript is a bit of a syntactic sugar sprinkled on top of JavaScript, and it fits in many developer scenarios since OOP is such a popular and reigning paradigm. Using TypeScript doesn’t mean you’re off the hook of knowing JavaScript well – the better you know JavaScript is the better you’ll know TypeScript.

To see how you can apply the OOP principles of TypeScript in Windows Store apps, check out my article on MSDN Magazine about Using TypeScript in Modern (Windows Store) apps and my blog posts tagged as TypeScript.

Use ViewModels to manage data & organize code in ASP.NET MVC applications

The concept of the ViewModel isn’t just for ASP.NET MVC, as you’ll see references to ViewModels throughout the web in articles and blog posts about the MVC, MVP, and MVVM patterns. Those posts and articles can center around any number of technologies such as ASP.NET, Silverlight, WPF, or MVC… This post will investigate ViewModels as they apply to the world of ASP.NET MVC.

What is an ASP.NET MVC ViewModel?

In ASP.NET MVC, ViewModels allow you to shape multiple entities from one or more data models or sources into a single object, optimized for consumption and rendering by the view. The below image illustrates the concept of a ViewModel:

 

image_16

The purpose of a ViewModel is for the view to have a single object to render, alleviating the need for UI logic code in the view that would otherwise be necessary. This means the only responsibility, or concern, of the view is to render that single ViewModel object, aiding in a cleaner separation of concerns (SoC). Concerns are distinct aspects of the application that have a particular purpose (i.e., concern), and keeping these aspects apart means your application is more organized, and the code more focused. Putting data manipulation code in its own location away from the view and controller, enforces SoC.

Using ViewModels in MVC for finer granularity and better SoC leads to more easily maintainable and testable code. Remember, unit testing is about testing small units.

Along with better coding practices, there are many business reasons demonstrating why you might consider using ViewModels:

  • Incorporating dropdown lists of lookup data into a related entity
  • Master-detail records view
  • Pagination: combining actual data and paging information
  • Components like a shopping cart or user profile widget
  • Dashboards, with multiple sources of disparate data
  • Reports, often with aggregate data

The above scenarios are common to a wide variety of applications, and deal with more complex data than basic CRUD forms-over-data page (e.g., a simple 1:1 mapping to the db table). For example, providing a list of states, and ensuring that the state that matches the state of current customer, means that you need to either provide two sets of data or a single set of customer/state data combined, as shown in the image below.

 

image_6

Some scenarios such as a lookup table representing states in the USA, could easily work with either ViewModels or a ViewBag/ViewData object, so there is some potential overlap at times. It’s up to the application architects and developers to decide what works best with their exact use case.

Creating a ViewModel

Although a ViewModel consists of multiple entities, at its core a ViewModel is still just a class – and one that doesn’t even inherit from anything special, as many MVC classes do.

Physically, ViewModels can exist in different locations, listed below:

  • In a folder called ViewModels that resides in the root of the project. (small apps)
  • As a .dll referenced from the MVC project (any size app)
  • In a separate project(s) as a service layer, for large applications that generate view/content specific data. (enterprise apps)

Since a ViewModel is just a class, the easiest way to get started using one is to create a new folder named ViewModels and add a new code file to it.

To create the CustomerViewModel ViewModel, add the Customer and StatesDictionary types as properties to form one CustomerViewModel class. In the example below, the CustomerViewModel class contains the newly defined properties.

public class CustomerViewModel 

{

    public Customer Customer { get; set; }

    public StatesDictionary States { get; set; }

    public CustomerViewModel(Customer customer)

    {

        Customer = customer;

        States = new StatesDictionary();

    }

}

Generally, ViewModels contain the word “ViewModel” as part of its name; however, the conventions at work here are for consistency in code readability, since other classes in MVC state their intents in their names as well (e.g., names of controllers, action methods, etc…use conventions in their names).

The StatesDictionary class is a simple Dictionary object containing two type parameters of type string. The class also contains the definitions for all the members in the Dictionary (i.e., the state data). The only property in the StatesDictionary class is the StateSelectList, which is an object that Html Helpers use with to render an HTML <select> element that displays a listing of states. The type Dictionary<string, string> in the StateSelectList property maps to the state abbreviation then state name, respectively.

public class StatesDictionary

{

    public static SelectList StateSelectList

    {

        get { return new SelectList(StateDictionary, "Value", "Key"); }

    } 

    public static readonly IDictionary<string, string> 

        StateDictionary = new Dictionary<string, string> { 

      {"Choose...",""}

    , { "Alabama", "AL" }

    , { "Alaska", "AK" }

    , { "Arizona", "AZ" }

    , { "Arkansas", "AR" }

    , { "California", "CA" }

    // code continues to add states...

    }; 

}

Data that lives in small lists and infrequently changes, like the StatesDictionary class, exists in all types of applications. In real world applications, you’ll find a variety of methods for dealing with lookup data such as a list of states – often XML files and SQL tables. You can replace the code in the StateDictionary method to use entities from Entity Framework, read data from files, or any data access code that you require.

After creating the ViewModel, the next steps are to instantiate it in a controller and return it to the view.

Getting the ViewModel to the view

Starts with the controller…

Sending a ViewModel to the view for rendering will work the same as when dealing with a model. Since it’s just a class, the view doesn’t know, and doesn’t care, where the model or ViewModel came from. You can create the instance of the ViewModel class in the controller, or resolve it if using an IoC container. Remember that just as you would do with views, you should keep controllers clean of unnecessary code, meaning that only code that fetches the model or ViewModel belongs here, and little more.

public ActionResult Edit(int id)

{

    Customer customer = context.Customers.Single(x => x.Id == id);

    var customerViewModel = new CustomerViewModel(customer);

    return View(customerViewModel);

}

Then the view renders the ViewModel…

In order for the view to know what object to use, set the @model keyword to point to the ViewModel, just like you already would with a regular model.

@model FourthCoffee.Web.ViewModels.CustomerViewModel

Because the Customer object is a property of the ViewModel, you’ll see the model.Class.Property syntax to access the ViewModel data, similar to the following line of code.

<div class="editor-label">

    @Html.LabelFor(model => model.Customer.FirstName)

</div>

<div class="editor-field">

    @Html.EditorFor(model => model.Customer.FirstName)

    @Html.ValidationMessageFor(model => model.Customer.FirstName)

</div>

@* ...View code continues rendering properties... *@

Additionally, you can edit the Edit/Create views so that the DropDownList containing a list of the states will display, and display the correct state matching that of the customer.

<div class="editor-field">    

    @Html.DropDownList("state", new SelectList(StatesDictionary.StateSelectList, 

                       "Value", "Text", Model.Customer == null ? "" : Model.Customer.State))

    @Html.ValidationMessageFor(model => model.Customer.State)

</div>

As you might have noticed, using a ViewModel is just as easy as using the ViewBag or ViewData objects. ViewModels, however, provide those extra benefits like being easier to test and optimize.

Checking the results

After a user navigates to the /Customers/Edit/1 URL in the browser, the Razor view engine renders the CustomerViewModel similarly to the following screen shot.

image_4

The State DropDownList displays the states and the current state for that customer, as expected.

Digging Further into ViewModels

Because ViewModels render pre-manipulated data that no longer have those 1:1 mappings between model classes and database tables, you’ll need to do create mappings yourself. You can manually map small ViewModels, but this will quickly become burdensome when mapping larger classes, especially when working with parent-child-grandchild, multi-level, or complex data. This is where a tool such as AutoMapper comes into play. AutoMapper will let you fluently setup mappings between ViewModels and models more easily than doing so manually, or writing your own mapper.

Here are some tips for using ViewModels:

  • Put only data that you’ll render in the ViewModel.
  • The view should direct the properties of the ViewModel, this way it fits better for rendering and maintenance.
  • Use a mapper when ViewModels become complex.

Some tools that can help assist you in generating POCOs (Plain Old CLR Objects) for models and ViewModels are:

POCO Generator

EF POCO Templates

In addition to these tools, you can use MvcScaffolding to create actions and views based on ViewModels. MvcScaffolding, invention of ASP.NET team member Steve Sanderson, gives you more power in creating CRUD, repository, unit test and other templates quickly and painlessly. Check out Steve’s Multi-part series on MvcScaffolding here. MvcScaffolding works with ViewModels as well as models.

You should always prefer using a ViewModel rather than instantiating multiple models and putting that manipulation code in the controller.

Summary

ViewModels help you organize and manage data in MVC applications when you need to work with more complex data than the other objects allow. Using ViewModels gives you the flexibility to use data as you see fit. ViewModels area generally a more flexible way to access multiple data sources than models + ViewBag/ViewData objects.

Further reading: Comparing the MVC and MVVM patterns along with their respective ViewModels

Download the code!

A 30 year sorting algorithm saga: from 250k to 14GB in one minute

Microsoft Research busted through the world record for sorting an unprecedented amount of data in under one minute, with a new sorting technique called MinuteSort (with flat datacenter storage). The Microsoft Research team sorted the equivalent of two 100-byte data records for every human being on the planet.

That’s a rough equivalent of a short email message, for example, this series of 1’s represents 200 bytes:

1111111111111111111111111111111111111111111111111111111111111111111111111111111111
1111111111111111111111111111111111111111111111111111111111111111111111111111111111

This is 200 bytes of a plain text message you might send in an email.

How much wood could a woodchuck chuck if a woodchuck could chuck wood?
Good woodchucks chuck much.

Multiply that by the population of planet Earth, currently at around 7 BILLION, and the result is 1,400,000,000,000 bytes, or over 14GB in one minute.

That’s a lot of data to wade through, and sorting hasn’t always been so fast and sexy. Take a look at this scan of an ancient TI-99 programming magazine article from 1983 on five popular sorting algorithms, some still used today.

  • Bubble Sort
  • Shell Sort
  • Selection Sort
  • Heap Sort
  • Quick Sort

Here’s a sampling of the article, page 1 & 2 (Download the complete 5 pages)

 

Ti-1_2ti-1a_2

 

Turn to the last page or the article and you can see that in 1983 the Quick Sort, wins the honor of sorting roughly 250k in about 1 minute and the Bubble sort can run equivalent of the 200 byte sample sample above in about 6 minutes (ouch).

image_12

How times have changed.

Sorting basics from Carnegie Mellon http://www.cs.cmu.edu/~adityaa/211/Lecture12AG.pdf [pdf]

Download the complete article

Big congrats to the awesome team at Microsoft Research! 100 points and a Geritol if you are old enough to have used a TI-99 or have read this magazine.

Partial views in ASP.NET MVC

What is a partial view and when should I use it?

As developers become familiar with the ASP.NET MVC model, they’ll naturally want to create reusable components filled with content & code. In Web Forms, we could do this by creating a web user control or a web server control, but in MVC, we will use partial views. You’ll notice that conceptually, all of the scenarios below would work for either technology.

  • A stock ticker that’s displayed on each page in an application.
  • A calendar widget that’s displayed on multiple pages in application.
  • A login box.
  • A social networking component used on multiple pages, such as a Facebook Like button.

While ASP.NET MVC partial views may behave similarly in theory to web user controls, syntactically and functionally, the two behave differently. Web user controls found in web forms uses ViewState, PostBacks, and Events while MVC partial views do not use any of the preceding techniques for managing state. Just as ASP.NET web user controls do, partial views can tap into the models contained in your application as well as share data between other application components.

Rendering partial views

Partial views in ASP.NET MVC 3 allow the developer to create reusable content with the very precise and clean Razor syntax (or ASPX). The syntax that renders the partial view is implemented as an Html helper. The Html.Partial helper renders the partial view named “_FeaturedProduct” inline. The first argument of all overloaded methods in the call the @Html.Partial expect the view/partial’s file name, without the file extension. Adhering to convention, the @Html.Partial helper assumes the view resides in the ViewsShared folder. Additional overloads in the @Html.Partial method allow you to pass ViewData/ViewBag objects between views/partials (see below under Sharing data…).

The code below demonstrates the call to render the featured product partial view.

<div>
  @Html.Partial("_FeaturedProduct")
</div
>

Partial views can be rendered inside a Layout Page (or if using MVC 2/3 w/ASPX, the Master Page) as well as regular views.

There are some cases where you might like to step aside and write directly to the HTTP Response stream rather than having a partial view render the results (partials/views use MvcHtmlString/StringWriter). To do so, use the Html.RenderPartial helper.

<div>
  @Html.RenderPartial(“_FeaturedProduct”)
</div
>

Use Html.RenderPartial for streaming images or other elements that are media-centric or where faster download times are highly important.

Creating a partial view

Both partial views and regular views are .cshtml files, with the difference being the folder where the partial views reside: ViewsShared. Use the Add New View dialog by accessing the context menu from the ViewsShared node in Solution Explorer. The Add New View template dialog offers choices for creating your partial views, including the option for strongly typing views. Don’t forget to check off  “Create as a partial view” or you’ll end up with a lot of code to delete.

SNAGHTML44dfac8

Once you’ve created the view you can get started customizing it by simply editing the file. There’s no problem in deleting or modifying the view’s code, as there’s no designer tied to it. The code shown below (_FeaturedProduct.cshtml) is the same code the default view template creates, but modified to display the featured product differently:

<style type=“text/css”>
    .featuredProduct {border: solid 1px #000}
</style
>
<
div>
    <div>
        <h2>
            Our Featured product:<br />
            @ViewBag.FeaturedProduct.Name
        </h2>
    </div>    <div>
        <h3>
            Now discounted to $@String.Format(“{0:F}”, ((decimal)ViewBag.FeaturedProduct.Price)-100)
        </h3>
    </div>  
    <div>
        @Html.ActionLink(“Featured Product Details”, “Details”, new { id = ViewBag.FeaturedProduct.ProductId })
    </div> 
    <div>
        <img class=“featuredProduct” src=@Href(“~/Content/Images”)/@ViewBag.FeaturedProduct.ImageName” alt=Featured Product”/>
    </div
>
</
div
>

As with strongly typed views, strongly typed partial views also support dot notation syntax and access to the model, ViewBag, ViewData and other classes specifically designed for sharing data.

It should be clear when reading through the above code that the syntax of partial view looks the same as a regular view. The important take-away is not about the syntax but how the partial view is used. However, a syntactic benefit to developers is the consistency between both partial and full views, particularly when we need to share data between them.

Sharing Data between views and partial views

It’s a common occurrence to pass data between components of an application, and in this case those components are MVC partials, views & controllers. As previously noted, you should use the ViewBag or ViewData classes to share data across views and controllers. First, a few notes on ViewBag and ViewData:

  • ViewData was available in previous versions; ViewBag was released with MVC 3.
  • ViewData can contain any type of data in a name-value pair format. I.e., ViewData[“Message”] = “Welcome”;
  • ViewBag objects are just wrappers around ViewData objects, and allow developers to code to them using strongly typed syntax.
  • ViewBag objects can be extended by simply setting properties in a more fluent syntax. I.e.,  ViewBag.Customer = new Customer(1,”Smith”);

If code in a controller uses either the ViewBag or ViewData classes, those classes will be available throughout the view’s lifecycle, and that includes its partial views.

The preferable object is the ViewBag. Because of its more fluent and dynamic syntax, there’s more complex objects that can be shared quite easily between components. The sample below demonstrates setting up the ViewBag object in the controller so it will be available to all necessary components:

ProductModel productModel = new ProductModel();        
public ActionResult Index()
{
    ViewBag.FeaturedProduct = new FeaturedProduct(105, "The Most Awesome Bike Ever!", 1000.00M, "bike4.png");          
    return View(productModel.Products);           
}

The ViewBag is accessed inside the view or partial using the follows syntax:

@ViewBag.FeaturedProduct.Name

Summary

Partial views are a great way to reuse fragments of HTML and Razor syntax together, with the ability to easily share data.

Resources:

Introducing Razor

Introducing MVC Development w/the Razor View Engine

Razor View Syntax