Click here to close now.



Welcome!

Microservices Expo Authors: Anders Wallgren, Pat Romanski, Jason Bloomberg, Liz McMillan, Elizabeth White

Related Topics: Microsoft Cloud

Microsoft Cloud: Article

Dealing With The C# 2.0 Genericity

Leverage generics for flexible code, the forthcoming .NET 2.0 Framework will introduce new important features

The forthcoming .NET 2.0 Framework will introduce new important features. One of those features is genericity. Genericity is not really a new concept. It has been included in some previous languages as ADA, C++, Eiffel, and in the mathematical model of abstract data types (ADT). However, the C# 2.0 notation for genericity (see the first entry in the References section), the integration of genericity in the .NET type system, the efficient implementation of genericity in the CLR-JIT process, and the new generic features included in the reflection mechanism will strengthen .NET programmers' output.

Genericity in .NET rests on the same basic reasons for which .NET promotes strongly typed languages:

  • Readability: Explicit declarations tell readers about the intended meaning of the code
  • Reliability: Thanks to explicit type declarations, a compiler can easily detect inconsistencies and erroneous operations
  • Efficiency: By knowing the types early, a compiler will be able to generate a more efficient code
The first section of this article starts by presenting arrays, the humble and anonymous generic construction embedded in C# and many programming languages. The second section explains how a limited form of generic types can be currently implemented in C#, based on the object type. In the third section the main characteristics and benefits of genericity in C# 2.0 are illustrated, including the notion of constrained genericity. An additional section explains how we can interact between generics and non-generics. Finally, we present an interesting example about simulation of multiple inheritance with genericity.

Arrays: The Implicit Generic Construction Embedded in .NET
Perhaps because arrays are predefined in C# and embedded in the CLR, when using them programmers don't realize that they are dealing with a truly an efficient generic construction.

When you write a declaration like int[] a you are instantiating a generic container, known as an array of items of type int. Any type T can be used to define an array through the notation T[]. A set of common properties and functionalities implicitly applies to arrays no matter what type T is:

  • All array objects are created with the notation new T[k] where k must be a positive expression that defines the numbers of items in the array.
  • An int property Length applies to every array (no matter the type T) to return the number of items of the array. Items are numbered from 0 to Length-1.
  • All items of an array of type T[] have the same type T. Items of a value type T are initialized as such value type (zero for numeric types, false for bool type, and so on) and items of a reference type T are initialized to null.
    1.  For an array T[] a, a[i] acts as a variable of type T denoting the item at position i. When using in the right side, a[i] returns an item of type T, and when using in a left side, a[i]=x; x must be of type T.
Unfortunately, before C# 2.0, programmers could not define a custom parameterized type based on a type T.

Genericity Based on the "Wild card type" Object
Today C# programmers who want to define a stack type of int objects must write the code in Listing 1a. If they wish to define a stack of objects of a type Person they could write the code in Listing 1b (for simplicity, this is only a rough implementation of a stack). Note that both classes Stackofint and StackofPerson have similar codes. They differ only in the type they are based on (int or Person). We can avoid that replication by defining a sole Stack type based on the root type object (see Listing 2).

Here object acts like a wild card type. Since every type in .NET inherits from the base object type, and thanks to the boxing and unboxing features of .NET, programmers can seamless push either a reference object or a value object into a stack. Note that the parameter of Push is of type object, then some calls like s.Push(3) or s.Push(new Person(...)) are correct, because any type conforms to object.

The approach above has the benefit of no code replication, but it has the following flaws:

  • It is not possible to enforce the kind of data to be placed in the stack. As the following code snippet shows, we could create a stack and push an assortment of objects on it.

    Stack s = new Stack(10);
    s.Push(new Date(10,10,2000);
    s.Push(new Person(...));
    s.Push(100);

  • Boxing and unboxing operations that apply when pushing and retrieving objects of value types can be particularly onerous.
  • Because the compiler only knows that objects in the stack have the general type object, when we retrieve the objects from the stack we must cast them to the real type they have:

    int k = (int) s.Pop();
    Person p = (Person) s.Pop();

However casting has a run-time cost, and even worse, it is an error-prone approach because it is possible to write a wrong cast.

It would be significant if we could have the safety and efficiency of specific type definitions (as shown in Listing 1), and, at the same time, we could avoid code replication. Both benefits could be achieved with the forthcoming genericity of C# 2.0.

Genericity in C# 2.0
In C# 2.0 the aforementioned definition of Stack could be best obtained by using the generic notation shown in Listing 3.

Here Stack<T> denotes a generic type and T denotes a type parameter of this generic type. Instantiating this type parameter with an actual type will result in a type of specific stack:

Stack<Person> persons = new Stack<Person>(10);.

Now persons has the type Stack<Per-son>. This has the following benefits:

  • All operations defined in Stack<T> are applied to Stack<Person> without programming duplication
  • Compiler can accept the following code without doing casting:

    Person harry = new Person(...);
    persons.Push(harry);
    Person p = persons.Pop();

  • In an attempt to push on persons, an object of a type not conforming to Person will result in a compilation error:

    persons.Push(23); //Error because 23 is not of type Person

    It is possible to push on the stack persons an object of a subtype of Person. If the class Employee inherits from Person, then the following code is correct:

    persons.Push(new Employee(...));

A type parameter can be used as an instantiation parameter of another generic type. Note that in the Stack<T> definition, the parameter T is used to instantiate the internal array T[] items. It means that when we write Stack<Person>, its instance variable items will be of type Person[].

Furthermore, generic instantiation can be done recursively. For example, a three-dimensional list can be defined as follows:

List<List<List<string>>> stringCube =
new List<List<List<string>>>(5);

Multiple Type Parameters
A generic type can have any number of type parameters. For example, in the generic dictionary type

class Dictionary<TKey, TValue> {...}

TKey must be instantiated with the type that we want to use as the type of the key (the object to search in the dictionary), and TValue must be instantiated as the type of the object associated with the key. Some examples are:

Dictionary<string, string> englishSpanish = new Dictionary<string, string>();
Dictionary<string, long> phoneList = new Dictionary<string, long>();
Dictionary<string, Person> contactList = new Dictionary<string, Person>();

More Stories By Miguel Katrib

Miguel Katrib is a PhD and a professor in the Computer Science Department at the University of Havana. He is also the head of the WEBOO group dedicated to Web and object-oriented technologies. Miguel is also a scientific advisor in .NET for the software enterprise CARE Technologies, Denia, Spain.

More Stories By Mario del Valle

Mario del Valle is working toward his MS at the Computer Science Department at the University of Havana, and is a software developer at the WEBOO group dedicated to Web and object-oriented technologies.

Comments (1) View Comments

Share your thoughts on this story.

Add your comment
You must be signed in to add a comment. Sign-in | Register

In accordance with our Comment Policy, we encourage comments that are on topic, relevant and to-the-point. We will remove comments that include profanity, personal attacks, racial slurs, threats of violence, or other inappropriate material that violates our Terms and Conditions, and will block users who make repeated violations. We ask all readers to expect diversity of opinion and to treat one another with dignity and respect.


Most Recent Comments
.NET News Desk 12/06/05 06:45:57 PM EST

The forthcoming .NET 2.0 Framework will introduce new important features. One of those features is genericity. Genericity is not really a new concept. It has been included in some previous languages as ADA, C++, Eiffel, and in the mathematical model of abstract data types (ADT). However, the C# 2.0 notation for genericity (see the first entry in the References section), the integration of genericity in the .NET type system, the efficient implementation of genericity in the CLR-JIT process, and the new generic features included in the reflection mechanism will strengthen .NET programmers' output.

@MicroservicesExpo Stories
As software organizations continue to invest in achieving Continuous Delivery (CD) of their applications, we see increased interest in microservices architectures, which–on the face of it–seem like a natural fit for enabling CD. In microservices (or its predecessor, “SOA”), the business functionality is decomposed into a set of independent, self-contained services that communicate with each other via an API. Each of the services has their own application release cycle, and are developed and depl...
With microservices, SOA and distributed architectures becoming more popular, it is becoming increasingly harder to keep track of where time is spent in a distributed application when trying to diagnose performance problems. Distributed tracing systems attempt to address this problem by following application requests across service boundaries, persisting metadata along the way that provide context for fine-grained performance monitoring.
The battle over bimodal IT is heating up. Now that there’s a reasonably broad consensus that Gartner’s advice about bimodal IT is deeply flawed – consensus everywhere except perhaps at Gartner – various ideas are springing up to fill the void. The bimodal problem, of course, is well understood. ‘Traditional’ or ‘slow’ IT uses hidebound, laborious processes that would only get in the way of ‘fast’ or ‘agile’ digital efforts. The result: incoherent IT strategies and shadow IT struggles that lead ...
More and more companies are looking to microservices as an architectural pattern for breaking apart applications into more manageable pieces so that agile teams can deliver new features quicker and more effectively. What this pattern has done more than anything to date is spark organizational transformations, setting the foundation for future application development. In practice, however, there are a number of considerations to make that go beyond simply “build, ship, and run,” which changes ho...
SYS-CON Events announced today that Commvault, a global leader in enterprise data protection and information management, has been named “Bronze Sponsor” of SYS-CON's 18th International Cloud Expo, which will take place on June 7–9, 2016, at the Javits Center in New York City, NY, and the 19th International Cloud Expo, which will take place on November 1–3, 2016, at the Santa Clara Convention Center in Santa Clara, CA. Commvault is a leading provider of data protection and information management...
SYS-CON Events announced today that AppNeta, the leader in performance insight for business-critical web applications, will exhibit and present at SYS-CON's @DevOpsSummit at Cloud Expo New York, which will take place on June 7-9, 2016, at the Javits Center in New York City, NY. AppNeta is the only application performance monitoring (APM) company to provide solutions for all applications – applications you develop internally, business-critical SaaS applications you use and the networks that deli...
SYS-CON Events announced today that Alert Logic, Inc., the leading provider of Security-as-a-Service solutions for the cloud, will exhibit at SYS-CON's 18th International Cloud Expo®, which will take place on June 7-9, 2016, at the Javits Center in New York City, NY. Alert Logic, Inc., provides Security-as-a-Service for on-premises, cloud, and hybrid infrastructures, delivering deep security insight and continuous protection for customers at a lower cost than traditional security solutions. Ful...
If we look at slow, traditional IT and jump to the conclusion that just because we found its issues intractable before, that necessarily means we will again, then it’s time for a rethink. As a matter of fact, the world of IT has changed over the last ten years or so. We’ve been experiencing unprecedented innovation across the board – innovation in technology as well as in how people organize and accomplish tasks. Let’s take a look at three differences between today’s modern, digital context...
SYS-CON Events announced today that VAI, a leading ERP software provider, will exhibit at SYS-CON's 18th International Cloud Expo®, which will take place on June 7-9, 2016, at the Javits Center in New York City, NY. VAI (Vormittag Associates, Inc.) is a leading independent mid-market ERP software developer renowned for its flexible solutions and ability to automate critical business functions for the distribution, manufacturing, specialty retail and service sectors. An IBM Premier Business Part...
SYS-CON Events announced today that Catchpoint Systems, Inc., a provider of innovative web and infrastructure monitoring solutions, has been named “Silver Sponsor” of SYS-CON's DevOps Summit at 18th Cloud Expo New York, which will take place June 7-9, 2016, at the Javits Center in New York City, NY. Catchpoint is a leading Digital Performance Analytics company that provides unparalleled insight into customer-critical services to help consistently deliver an amazing customer experience. Designed...
The (re?)emergence of Microservices was especially prominent in this week’s news. What are they good for? do they make sense for your application? should you take the plunge? and what do Microservices mean for your DevOps and Continuous Delivery efforts? Continue reading for more on Microservices, containers, DevOps culture, and more top news from the past week. As always, stay tuned to all the news coming from@ElectricCloud on DevOps and Continuous Delivery throughout the week and retweet/favo...
In most cases, it is convenient to have some human interaction with a web (micro-)service, no matter how small it is. A traditional approach would be to create an HTTP interface, where user requests will be dispatched and HTML/CSS pages must be served. This approach is indeed very traditional for a web site, but not really convenient for a web service, which is not intended to be good looking, 24x7 up and running and UX-optimized. Instead, talking to a web service in a chat-bot mode would be muc...
In the Bimodal model we find two areas of IT - the traditional kind where the main concern is keeping the lights on and the IT focusing on agility and speed, where everything needs to be faster. Today companies are investing in new technologies and processes to emulate their most agile competitors. Gone are the days of waterfall development and releases only every few months. Today's IT and the business it powers demands performance akin to a supercar - everything needs to be faster, every sc...
At the heart of the Cloud Native model is a microservices application architecture, and applying this to a telco SDN scenario offers enormous opportunity for product innovation and competitive advantage. For example in the ETSI NFV Ecosystem white paper they describe one of the product markets that SDN might address to be the Home sector. Vendors like Alcatel market SDN-based solutions for the home market, offering Home Gateways – A virtual residential gateway (vRGW) where service provider...
SYS-CON Events announced today that Interoute, owner-operator of one of Europe's largest networks and a global cloud services platform, has been named “Bronze Sponsor” of SYS-CON's 18th Cloud Expo, which will take place on June 7-9, 2015 at the Javits Center in New York, New York. Interoute is the owner-operator of one of Europe's largest networks and a global cloud services platform which encompasses 12 data centers, 14 virtual data centers and 31 colocation centers, with connections to 195 ad...
Web performance issues and advances have been gaining a stronger presence in the headlines as people are becoming more aware of its impact on virtually every business, and 2015 was no exception. We saw a myriad of major outages this year hit some of the biggest corporations, as well as some technology integrations and other news that we IT Ops aficionados find very exciting. This past year has offered several opportunities for growth and evolution in the performance realm — even the worst failu...
Are you someone who knows that the number one rule in DevOps is “Don’t Panic”? Especially when it comes to making Continuous Delivery changes inside your organization? Are you someone that theorizes that if anyone implements real automation changes, the solution will instantly become antiquated and be replaced by something even more bizarre and inexplicable?
Welcome to the first top DevOps news roundup of 2016! At the end of last year, we saw some great predictions for 2016. While we’re excited to kick off the new year, this week’s top posts reminded us to take a second to slow down and really understand the current state of affairs. For example, do you actually know what microservices are – or aren’t? What about DevOps? Does the emphasis still fall mostly on the development side? This week’s top news definitely got the wheels turning and just migh...
Test automation is arguably the most important innovation to the process of QA testing in software development. The ability to automate regression testing and other repetitive test cases can significantly reduce the overall production time for even the most complex solutions. As software continues to be developed for new platforms – including mobile devices and the diverse array of endpoints that will be created during the rise of the Internet of Things - automation integration will have a huge ...
Providing a full-duplex communication channel over a single TCP connection, WebSocket is the most efficient protocol for real-time responses over the web. If you’re utilizing WebSocket technology, performance testing will boil down to simulating the bi-directional nature of your application. Introduced with HTML5, the WebSocket protocol allows for more interaction between a browser and website, facilitating real-time applications and live content. WebSocket technology creates a persistent conne...