Welcome!

Microsoft Cloud Authors: Liz McMillan, Elizabeth White, Mihai Corbuleac, Pat Romanski, David Bermingham

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.

@ThingsExpo Stories
The essence of data analysis involves setting up data pipelines that consist of several operations that are chained together – starting from data collection, data quality checks, data integration, data analysis and data visualization (including the setting up of interaction paths in that visualization). In our opinion, the challenges stem from the technology diversity at each stage of the data pipeline as well as the lack of process around the analysis.
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...
Designing IoT applications is complex, but deploying them in a scalable fashion is even more complex. A scalable, API first IaaS cloud is a good start, but in order to understand the various components specific to deploying IoT applications, one needs to understand the architecture of these applications and figure out how to scale these components independently. In his session at @ThingsExpo, Nara Rajagopalan is CEO of Accelerite, will discuss the fundamental architecture of IoT applications, ...
SYS-CON Events announced today that Tintri Inc., a leading producer of VM-aware storage (VAS) for virtualization and cloud environments, will exhibit at the 18th International CloudExpo®, which will take place on June 7-9, 2016, at the Javits Center in New York City, New York, 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.
With major technology companies and startups seriously embracing IoT strategies, now is the perfect time to attend @ThingsExpo 2016 in New York and Silicon Valley. Learn what is going on, contribute to the discussions, and ensure that your enterprise is as "IoT-Ready" as it can be! Internet of @ThingsExpo, taking place Nov 3-5, 2015, at the Santa Clara Convention Center in Santa Clara, CA, is co-located with 17th Cloud Expo and will feature technical sessions from a rock star conference faculty ...
Companies can harness IoT and predictive analytics to sustain business continuity; predict and manage site performance during emergencies; minimize expensive reactive maintenance; and forecast equipment and maintenance budgets and expenditures. Providing cost-effective, uninterrupted service is challenging, particularly for organizations with geographically dispersed operations.
As cloud and storage projections continue to rise, the number of organizations moving to the cloud is escalating and it is clear cloud storage is here to stay. However, is it secure? Data is the lifeblood for government entities, countries, cloud service providers and enterprises alike and losing or exposing that data can have disastrous results. There are new concepts for data storage on the horizon that will deliver secure solutions for storing and moving sensitive data around the world. ...
18th Cloud Expo, taking place June 7-9, 2016, at the Javits Center in New York City, NY, 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 enterprises are using some...
SYS-CON Events announced today that MangoApps 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. MangoApps provides modern company intranets and team collaboration software, allowing workers to stay connected and productive from anywhere in the world and from any device. For more information, please visit https://www.mangoapps.com/.
SoftLayer operates a global cloud infrastructure platform built for Internet scale. With a global footprint of data centers and network points of presence, SoftLayer provides infrastructure as a service to leading-edge customers ranging from Web startups to global enterprises. SoftLayer's modular architecture, full-featured API, and sophisticated automation provide unparalleled performance and control. Its flexible unified platform seamlessly spans physical and virtual devices linked via a world...
In his keynote at 18th Cloud Expo, Andrew Keys, Co-Founder of ConsenSys Enterprise, will provide an overview of the evolution of the Internet and the Database and the future of their combination – the Blockchain. Andrew Keys is Co-Founder of ConsenSys Enterprise. He comes to ConsenSys Enterprise with capital markets, technology and entrepreneurial experience. Previously, he worked for UBS investment bank in equities analysis. Later, he was responsible for the creation and distribution of life ...
In his session at 18th Cloud Expo, Bruce Swann, Senior Product Marketing Manager at Adobe, will discuss how the Adobe Marketing Cloud can help marketers embrace opportunities for personalized, relevant and real-time customer engagement across offline (direct mail, point of sale, call center) and digital (email, website, SMS, mobile apps, social networks, connected objects). Bruce Swann has more than 15 years of experience working with digital marketing disciplines like web analytics, social med...
SYS-CON Events announced today that BMC Software has been named "Siver 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. BMC is a global leader in innovative software solutions that help businesses transform into digital enterprises for the ultimate competitive advantage. BMC Digital Enterprise Management is a set of innovative IT solutions designed to make digital business fast, seamless, and optimized from mainframe to mo...
Join us at Cloud Expo | @ThingsExpo 2016 – June 7-9 at the Javits Center in New York City and November 1-3 at the Santa Clara Convention Center in Santa Clara, CA – and deliver your unique message in a way that is striking and unforgettable by taking advantage of SYS-CON's unmatched high-impact, result-driven event / media packages.
SYS-CON Events announced today that EastBanc Technologies 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. EastBanc Technologies has been working at the frontier of technology since 1999. Today, the firm provides full-lifecycle software development delivering flexible technology solutions that seamlessly integrate with existing systems – whether on premise or cloud. EastBanc Technologies partners with p...
SYS-CON Events announced today that ContentMX, the marketing technology and services company with a singular mission to increase engagement and drive more conversations for enterprise, channel and SMB technology marketers, has been named “Sponsor & Exhibitor Lounge Sponsor” of SYS-CON's 18th Cloud Expo, which will take place on June 7-9, 2016, at the Javits Center in New York City, New York. “CloudExpo is a great opportunity to start a conversation with new prospects, but what happens after the...
The 19th International Cloud Expo has announced that its Call for Papers is open. Cloud Expo, to be held November 1-3, 2016, at the Santa Clara Convention Center in Santa Clara, CA, brings together Cloud Computing, Big Data, Internet of Things, DevOps, Containers, Microservices and WebRTC to one location. With cloud computing driving a higher percentage of enterprise IT budgets every year, it becomes increasingly important to plant your flag in this fast-expanding business opportunity. Submit y...
Internet of @ThingsExpo, taking place November 1-3, 2016, at the Santa Clara Convention Center in Santa Clara, CA, is co-located with the 19th International Cloud Expo and will feature technical sessions from a rock star conference faculty and the leading industry players in the world and ThingsExpo New York Call for Papers is now open.
The IoTs will challenge the status quo of how IT and development organizations operate. Or will it? Certainly the fog layer of IoT requires special insights about data ontology, security and transactional integrity. But the developmental challenges are the same: People, Process and Platform. In his session at @ThingsExpo, Craig Sproule, CEO of Metavine, will demonstrate how to move beyond today's coding paradigm and share the must-have mindsets for removing complexity from the development proc...
The IoT is changing the way enterprises conduct business. In his session at @ThingsExpo, Eric Hoffman, Vice President at EastBanc Technologies, discuss how businesses can gain an edge over competitors by empowering consumers to take control through IoT. We'll cite examples such as a Washington, D.C.-based sports club that leveraged IoT and the cloud to develop a comprehensive booking system. He'll also highlight how IoT can revitalize and restore outdated business models, making them profitable...