Welcome!

IoT User Interface Authors: Elizabeth White, Ed Featherston, William Schmarzo, Roger Strukhoff, James Pathman

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.

@CloudExpo Stories
The vision of a connected smart home is becoming reality with the application of integrated wireless technologies in devices and appliances. The use of standardized and TCP/IP networked wireless technologies in line-powered and battery operated sensors and controls has led to the adoption of radios in the 2.4GHz band, including Wi-Fi, BT/BLE and 802.15.4 applied ZigBee and Thread. This is driving the need for robust wireless coexistence for multiple radios to ensure throughput performance and th...
Internet of @ThingsExpo, taking place November 1-3, 2016, at the Santa Clara Convention Center in Santa Clara, CA, is co-located with 19th Cloud Expo and will feature technical sessions from a rock star conference faculty and the leading industry players in the world. The Internet of Things (IoT) is the most profound change in personal and enterprise IT since the creation of the Worldwide Web more than 20 years ago. All major researchers estimate there will be tens of billions devices - comp...
The many IoT deployments around the world are busy integrating smart devices and sensors into their enterprise IT infrastructures. Yet all of this technology – and there are an amazing number of choices – is of no use without the software to gather, communicate, and analyze the new data flows. Without software, there is no IT. In this power panel at @ThingsExpo, moderated by Conference Chair Roger Strukhoff, panelists will look at the protocols that communicate data and the emerging data analy...
Most of us already know that adopting new cloud applications can boost a business’s productivity by enabling organizations to be more agile and ready to change course in our fast-moving and connected digital world. But the rapid adoption of cloud apps and services also brings with it profound security threats, including visibility and control challenges that aren’t present in traditional on-premises environments. At the same time, the cloud – because of its interconnected, flexible and adaptable...
According to Forrester Research, every business will become either a digital predator or digital prey by 2020. To avoid demise, organizations must rapidly create new sources of value in their end-to-end customer experiences. True digital predators also must break down information and process silos and extend digital transformation initiatives to empower employees with the digital resources needed to win, serve, and retain customers.
“We're a global managed hosting provider. Our core customer set is a U.S.-based customer that is looking to go global,” explained Adam Rogers, Managing Director at ANEXIA, in this SYS-CON.tv interview at 18th Cloud Expo, held June 7-9, 2016, at the Javits Center in New York City, NY.
Why do your mobile transformations need to happen today? Mobile is the strategy that enterprise transformation centers on to drive customer engagement. In his general session at @ThingsExpo, Roger Woods, Director, Mobile Product & Strategy – Adobe Marketing Cloud, covered key IoT and mobile trends that are forcing mobile transformation, key components of a solid mobile strategy and explored how brands are effectively driving mobile change throughout the enterprise.
The Jevons Paradox suggests that when technological advances increase efficiency of a resource, it results in an overall increase in consumption. Writing on the increased use of coal as a result of technological improvements, 19th-century economist William Stanley Jevons found that these improvements led to the development of new ways to utilize coal. In his session at 19th Cloud Expo, Mark Thiele, Chief Strategy Officer for Apcera, will compare the Jevons Paradox to modern-day enterprise IT, e...
In this strange new world where more and more power is drawn from business technology, companies are effectively straddling two paths on the road to innovation and transformation into digital enterprises. The first path is the heritage trail – with “legacy” technology forming the background. Here, extant technologies are transformed by core IT teams to provide more API-driven approaches. Legacy systems can restrict companies that are transitioning into digital enterprises. To truly become a lea...
DevOps at Cloud Expo, taking place Nov 1-3, 2016, at the Santa Clara Convention Center in Santa Clara, CA, is co-located with 19th Cloud Expo and will feature technical sessions from a rock star conference faculty and the leading industry players in the world. The widespread success of cloud computing is driving the DevOps revolution in enterprise IT. Now as never before, development teams must communicate and collaborate in a dynamic, 24/7/365 environment. There is no time to wait for long dev...
Cloud computing is being adopted in one form or another by 94% of enterprises today. Tens of billions of new devices are being connected to The Internet of Things. And Big Data is driving this bus. An exponential increase is expected in the amount of information being processed, managed, analyzed, and acted upon by enterprise IT. This amazing is not part of some distant future - it is happening today. One report shows a 650% increase in enterprise data by 2020. Other estimates are even higher....
What are the new priorities for the connected business? First: businesses need to think differently about the types of connections they will need to make – these span well beyond the traditional app to app into more modern forms of integration including SaaS integrations, mobile integrations, APIs, device integration and Big Data integration. It’s important these are unified together vs. doing them all piecemeal. Second, these types of connections need to be simple to design, adapt and configure...
Let’s face it, embracing new storage technologies, capabilities and upgrading to new hardware often adds complexity and increases costs. In his session at 18th Cloud Expo, Seth Oxenhorn, Vice President of Business Development & Alliances at FalconStor, discussed how a truly heterogeneous software-defined storage approach can add value to legacy platforms and heterogeneous environments. The result reduces complexity, significantly lowers cost, and provides IT organizations with improved efficienc...
SYS-CON Events announced today that CDS Global Cloud, an Infrastructure as a Service provider, will exhibit at the 19th International Cloud Expo, which will take place on November 1–3, 2016, at the Santa Clara Convention Center in Santa Clara, CA. CDS Global Cloud is an IaaS (Infrastructure as a Service) provider specializing in solutions for e-commerce, internet gaming, online education and other internet applications. With a growing number of data centers and network points around the world, ...
In his general session at 18th Cloud Expo, Lee Atchison, Principal Cloud Architect and Advocate at New Relic, discussed cloud as a ‘better data center’ and how it adds new capacity (faster) and improves application availability (redundancy). The cloud is a ‘Dynamic Tool for Dynamic Apps’ and resource allocation is an integral part of your application architecture, so use only the resources you need and allocate /de-allocate resources on the fly.
19th Cloud Expo, taking place November 1-3, 2016, at the Santa Clara Convention Center in Santa Clara, CA, will feature technical sessions from a rock star conference faculty and the leading industry players in the world. Cloud computing is now being embraced by a majority of enterprises of all sizes. Yesterday's debate about public vs. private has transformed into the reality of hybrid cloud: a recent survey shows that 74% of enterprises have a hybrid cloud strategy. Meanwhile, 94% of enterpri...
Information technology is an industry that has always experienced change, and the dramatic change sweeping across the industry today could not be truthfully described as the first time we've seen such widespread change impacting customer investments. However, the rate of the change, and the potential outcomes from today's digital transformation has the distinct potential to separate the industry into two camps: Organizations that see the change coming, embrace it, and successful leverage it; and...
Major trends and emerging technologies – from virtual reality and IoT, to Big Data and algorithms – are helping organizations innovate in the digital era. However, to create real business value, IT must think beyond the ‘what’ of digital transformation to the ‘how’ to harness emerging trends, innovation and disruption. Architecture is the key that underpins and ties all these efforts together. In the digital age, it’s important to invest in architecture, extend the enterprise footprint to the cl...
There are several IoTs: the Industrial Internet, Consumer Wearables, Wearables and Healthcare, Supply Chains, and the movement toward Smart Grids, Cities, Regions, and Nations. There are competing communications standards every step of the way, a bewildering array of sensors and devices, and an entire world of competing data analytics platforms. To some this appears to be chaos. In this power panel at @ThingsExpo, moderated by Conference Chair Roger Strukhoff, Bradley Holt, Developer Advocate a...
SYS-CON Events announced today that LeaseWeb USA, a cloud Infrastructure-as-a-Service (IaaS) provider, will exhibit at the 19th International Cloud Expo, which will take place on November 1–3, 2016, at the Santa Clara Convention Center in Santa Clara, CA. LeaseWeb is one of the world's largest hosting brands. The company helps customers define, develop and deploy IT infrastructure tailored to their exact business needs, by combining various kinds cloud solutions.