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                                                        The Creation of C#

            # is Microsoft’s premier language for .NET development. It leverages time-tested
            features with cutting-edge innovations and provides a highly usable, efficient way
            to write programs for the modern enterprise computing environment. It is, by any
    measure, one of the most important languages of the 21st century.
        The purpose of this chapter is to place C# into its historical context, including the forces
    that drove its creation, its design philosophy, and how it was influenced by other computer
    languages. This chapter also explains how C# relates to the .NET Framework. As you will
    see, C# and the .NET Framework work together to create a highly refined programming

C#’s Family Tree
    Computer languages do not exist in a void. Rather, they relate to one another, with each new
    language influenced in one form or another by the ones that came before. In a process akin to
    cross-pollination, features from one language are adapted by another, a new innovation is
    integrated into an existing context, or an older construct is removed. In this way, languages
    evolve and the art of programming advances. C# is no exception.
        C# inherits a rich programming legacy. It is directly descended from two of the world’s
    most successful computer languages: C and C++. It is closely related to another: Java.
    Understanding the nature of these relationships is crucial to understanding C#. Thus, we
    begin our examination of C# by placing it in the historical context of these three languages.

    C: The Beginning of the Modern Age of Programming
    The creation of C marks the beginning of the modern age of programming. C was invented
    by Dennis Ritchie in the 1970s on a DEC PDP-11 that used the UNIX operating system.
    While some earlier languages, most notably Pascal, had achieved significant success, C
    established the paradigm that still charts the course of programming today.
        C grew out of the structured programming revolution of the 1960s. Prior to structured
    programming, large programs were difficult to write because the program logic tended to
    degenerate into what is known as “spaghetti code,” a tangled mass of jumps, calls, and
    returns that is difficult to follow. Structured languages addressed this problem by adding
    well-defined control statements, subroutines with local variables, and other improvements.
    Through the use of structured techniques programs became better organized, more reliable,
    and easier to manage.
4   Part I:     The C# Language

         Although there were other structured languages at the time, C was the first to successfully
    combine power, elegance, and expressiveness. Its terse, yet easy-to-use syntax coupled with
    its philosophy that the programmer (not the language) was in charge quickly won many
    converts. It can be a bit hard to understand from today’s perspective, but C was a breath of
    fresh air that programmers had long awaited. As a result, C became the most widely used
    structured programming language of the 1980s.
         However, even the venerable C language had its limits. One of the most troublesome
    was its inability to handle large programs. The C language hits a barrier once a project
    reaches a certain size, and after that point, C programs are difficult to understand and
    maintain. Precisely where this limit is reached depends upon the program, the programmer,
    and the tools at hand, but there is always a threshold beyond which a C program becomes

    The Creation of OOP and C++
    By the late 1970s, the size of many projects was near or at the limits of what structured
    programming methodologies and the C language could handle. To solve this problem, a
    new way to program began to emerge. This method is called object-oriented programming
    (OOP). Using OOP, a programmer could handle much larger programs. The trouble was
    that C, the most popular language at the time, did not support object-oriented programming.
    The desire for an object-oriented version of C ultimately led to the creation of C++.
        C++ was invented by Bjarne Stroustrup beginning in 1979 at Bell Laboratories in Murray
    Hill, New Jersey. He initially called the new language “C with Classes.” However, in 1983 the
    name was changed to C++. C++ contains the entire C language. Thus, C is the foundation
    upon which C++ is built. Most of the additions that Stroustrup made to C were designed to
    support object-oriented programming. In essence, C++ is the object-oriented version of C. By
    building upon the foundation of C, Stroustrup provided a smooth migration path to OOP.
    Instead of having to learn an entirely new language, a C programmer needed to learn only
    a few new features before reaping the benefits of the object-oriented methodology.
        C++ simmered in the background during much of the 1980s, undergoing extensive
    development. By the beginning of the 1990s, C++ was ready for mainstream use, and its
    popularity exploded. By the end of the decade, it had become the most widely used
    programming language. Today, C++ is still the preeminent language for the development of
    high-performance system code.
        It is critical to understand that the invention of C++ was not an attempt to create an
    entirely new programming language. Instead, it was an enhancement to an already highly
    successful language. This approach to language development—beginning with an existing
    language and moving it forward—established a trend that continues today.

    The Internet and Java Emerge
    The next major advance in programming languages is Java. Work on Java, which was
    originally called Oak, began in 1991 at Sun Microsystems. The main driving force behind
    Java’s design was James Gosling. Patrick Naughton, Chris Warth, Ed Frank, and Mike
    Sheridan also played a role.
        Java is a structured, object-oriented language with a syntax and philosophy derived from
    C++. The innovative aspects of Java were driven not so much by advances in the art of
    programming (although some certainly were), but rather by changes in the computing
    environment. Prior to the mainstreaming of the Internet, most programs were written,
                                                          Chapter 1:       The Creation of C#           5

compiled, and targeted for a specific CPU and a specific operating system. While it has always
been true that programmers like to reuse their code, the ability to port a program easily from
one environment to another took a backseat to more pressing problems. However, with the

                                                                                                            PART I
                                                                                                            PART I
                                                                                                            PART I
rise of the Internet, in which many different types of CPUs and operating systems are
connected, the old problem of portability reemerged with a vengeance. To solve the problem
of portability, a new language was needed, and this new language was Java.
     Although the single most important aspect of Java (and the reason for its rapid acceptance)
is its ability to create cross-platform, portable code, it is interesting to note that the original
impetus for Java was not the Internet, but rather the need for a platform-independent
language that could be used to create software for embedded controllers. In 1993, it became
clear that the issues of cross-platform portability found when creating code for embedded
controllers are also encountered when attempting to create code for the Internet. Remember:
the Internet is a vast, distributed computing universe in which many different types of
computers live. The same techniques that solved the portability problem on a small scale
could be applied to the Internet on a large scale.
     Java achieved portability by translating a program’s source code into an intermediate
language called bytecode. This bytecode was then executed by the Java Virtual Machine
(JVM). Therefore, a Java program could run in any environment for which a JVM was
available. Also, since the JVM is relatively easy to implement, it was readily available for
a large number of environments.
     Java’s use of bytecode differed radically from both C and C++, which were nearly
always compiled to executable machine code. Machine code is tied to a specific CPU and
operating system. Thus, if you wanted to run a C/C++ program on a different system, it
needed to be recompiled to machine code specifically for that environment. Therefore, to
create a C/C++ program that would run in a variety of environments, several different
executable versions of the program would be needed. Not only was this impractical, it was
expensive. Java’s use of an intermediate language was an elegant, cost-effective solution.
It is also a solution that C# would adapt for its own purposes.
     As mentioned, Java is descended from C and C++. Its syntax is based on C, and its object
model is evolved from C++. Although Java code is neither upwardly nor downwardly
compatible with C or C++, its syntax is sufficiently similar that the large pool of existing
C/C++ programmers could move to Java with very little effort. Furthermore, because Java
built upon and improved an existing paradigm, Gosling, et al., were free to focus their
attention on the new and innovative features. Just as Stroustrup did not need to “reinvent
the wheel” when creating C++, Gosling did not need to create an entirely new language
when developing Java. Moreover, with the creation of Java, C and C++ became an accepted
substrata upon which to base a new computer language.

The Creation of C#
While Java has successfully addressed many of the issues surrounding portability in the
Internet environment, there are still features that it lacks. One is cross-language interoperability,
also called mixed-language programming. This is the ability for the code produced by one
language to work easily with the code produced by another. Cross-language interoperability
is needed for the creation of large, distributed software systems. It is also desirable for
programming software components because the most valuable component is one that can
be used by the widest variety of computer languages, in the greatest number of operating
6   Part I:     The C# Language

        Another feature lacking in Java is full integration with the Windows platform. Although
    Java programs can be executed in a Windows environment (assuming that the Java Virtual
    Machine has been installed), Java and Windows are not closely coupled. Since Windows is
    the most widely used operating system in the world, lack of direct support for Windows is a
    drawback to Java.
        To answer these and other needs, Microsoft developed C#. C# was created at Microsoft
    late in the 1990s and was part of Microsoft’s overall .NET strategy. It was first released in its
    alpha version in the middle of 2000. C#’s chief architect was Anders Hejlsberg. Hejlsberg is
    one of the world’s leading language experts, with several notable accomplishments to his
    credit. For example, in the 1980s he was the original author of the highly successful and
    influential Turbo Pascal, whose streamlined implementation set the standard for all future
        C# is directly related to C, C++, and Java. This is not by accident. These are three of
    the most widely used—and most widely liked—programming languages in the world.
    Furthermore, at the time of C#’s creation, nearly all professional programmers knew C, C++,
    and/or Java. By building C# upon a solid, well-understood foundation, C# offered an easy
    migration path from these languages. Since it was neither necessary nor desirable for Hejlsberg
    to “reinvent the wheel,” he was free to focus on specific improvements and innovations.
        The family tree for C# is shown in Figure 1-1. The grandfather of C# is C. From C, C#
    derives its syntax, many of its keywords, and its operators. C# builds upon and improves
    the object model defined by C++. If you know C or C++, then you will feel at home with C#.
        C# and Java have a bit more complicated relationship. As explained, Java is also
    descended from C and C++. It too shares the C/C++ syntax and object model. Like Java, C#
    is designed to produce portable code. However, C# is not descended from Java. Instead, C#
    and Java are more like cousins, sharing a common ancestry, but differing in many important
    ways. The good news, though, is that if you know Java, then many C# concepts will be
    familiar. Conversely, if in the future you need to learn Java, then many of the things you
    learn about C# will carry over.
        C# contains many innovative features that we will examine at length throughout the
    course of this book, but some of its most important relate to its built-in support for software
    components. In fact, C# has been characterized as being a component-oriented language
    because it contains integral support for the writing of software components. For example,

    FIGURE 1-1
    The C# family tree
                                                             Chapter 1:      The Creation of C#          7

    C# includes features that directly support the constituents of components, such as
    properties, methods, and events. However, C#’s ability to work in a secure, mixed-language
    environment is perhaps its most important component-oriented feature.

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                                                                                                             PART I
    The Evolution of C#
    Since its original 1.0 release, C# has been evolving at a rapid pace. Not long after C# 1.0,
    Microsoft released version 1.1. It contained many minor tweaks but added no major
    features. However, the situation was much different with the release of C# 2.0.
         C# 2.0 was a watershed event in the lifecycle of C# because it added many new features,
    such as generics, partial types, and anonymous methods, that fundamentally expanded
    the scope, power, and range of the language. Version 2.0 firmly put C# at the forefront of
    computer language development. It also demonstrated Microsoft’s long-term commitment
    to the language.
         The next major release of C# was 3.0, and this is the version of C# described by this book.
    Because of the many new features added by C# 2.0, one might have expected the development
    of C# to slow a bit, just to let programmers catch up, but this was not the case. With the release
    of C# 3.0, Microsoft once again put C# on the cutting edge of language design, this time
    adding a set of innovative features that redefined the programming landscape. Here is
    a list of what 3.0 has added to the language:

         • Anonymous types
         • Auto-implemented properties
         • Extension methods
         • Implicitly typed variables
         • Lambda expressions
         • Language-integrated query (LINQ)
         • Object and collection initializers
         • Partial methods

        Although all of these features are important and have significant impact on the language,
    the two that are the most exciting are language-integrated query (LINQ) and lambda
    expressions. LINQ enables you to write database-style queries using C# programming
    elements. However, the LINQ syntax is not limited to only databases. It can also be used
    with arrays and collections. Thus, LINQ offers a new way to approach several common
    programming tasks. Lambda expressions are often used in LINQ expressions, but can also be
    used elsewhere. They implement a functional-style syntax that uses the lambda operator =>.
    Together, LINQ and lambda expressions add an entirely new dimension to C# programming.
    Throughout the course of this book, you will see how these features are revolutionizing the
    way that C# code is written.

How C# Relates to the .NET Framework
    Although C# is a computer language that can be studied on its own, it has a special
    relationship to its runtime environment, the .NET Framework. The reason for this is
    twofold. First, C# was initially designed by Microsoft to create code for the .NET
8   Part I:     The C# Language

    Framework. Second, the libraries used by C# are the ones defined by the .NET Framework.
    Thus, even though it is theoretically possible to separate C# the language from the .NET
    environment, in practice the two are closely linked. Because of this, it is important to have a
    general understanding of the .NET Framework and why it is important to C#.

    What Is the .NET Framework?
    The .NET Framework defines an environment that supports the development and execution
    of highly distributed, component-based applications. It enables differing computer languages
    to work together and provides for security, program portability, and a common programming
    model for the Windows platform. As it relates to C#, the .NET Framework defines two very
    important entities. The first is the Common Language Runtime (CLR). This is the system that
    manages the execution of your program. Along with other benefits, the Common Language
    Runtime is the part of the .NET Framework that enables programs to be portable, supports
    mixed-language programming, and provides for secure execution.
        The second entity is the .NET class library. This library gives your program access to the
    runtime environment. For example, if you want to perform I/O, such as displaying something
    on the screen, you will use the .NET class library to do it. If you are new to programming,
    then the term class may be new. Although it is explained in detail later in this book, for now
    a brief definition will suffice: a class is an object-oriented construct that helps organize
    programs. As long as your program restricts itself to the features defined by the .NET class
    library, your programs can run anywhere that the .NET runtime system is supported. Since
    C# automatically uses the .NET Framework class library, C# programs are automatically
    portable to all .NET environments.

How the Common Language Runtime Works
    The Common Language Runtime manages the execution of .NET code. Here is how it
    works: When you compile a C# program, the output of the compiler is not executable code.
    Instead, it is a file that contains a special type of pseudocode called Microsoft Intermediate
    Language (MSIL). MSIL defines a set of portable instructions that are independent of any
    specific CPU. In essence, MSIL defines a portable assembly language. One other point:
    although MSIL is similar in concept to Java’s bytecode, the two are not the same.
        It is the job of the CLR to translate the intermediate code into executable code when a
    program is run. Thus, any program compiled to MSIL can be run in any environment for
    which the CLR is implemented. This is part of how the .NET Framework achieves portability.
        Microsoft Intermediate Language is turned into executable code using a JIT compiler.
    “JIT” stands for “Just-In-Time.” The process works like this: When a .NET program is
    executed, the CLR activates the JIT compiler. The JIT compiler converts MSIL into native
    code on demand as each part of your program is needed. Thus, your C# program actually
    executes as native code even though it is initially compiled into MSIL. This means that your
    program runs nearly as fast as it would if it had been compiled to native code in the first
    place, but it gains the portability benefits of MSIL.
        In addition to MSIL, one other thing is output when you compile a C# program:
    metadata. Metadata describes the data used by your program and enables your code to
    interact easily with other code. The metadata is contained in the same file as the MSIL.
                                                          Chapter 1:      The Creation of C#         9

Managed vs. Unmanaged Code
   In general, when you write a C# program, you are creating what is called managed code.

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   Managed code is executed under the control of the Common Language Runtime as just
   described. Because it is running under the control of the CLR, managed code is subject to
   certain constraints—and derives several benefits. The constraints are easily described and
   met: the compiler must produce an MSIL file targeted for the CLR (which C# does) and use
   the .NET class library (which C# does). The benefits of managed code are many, including
   modern memory management, the ability to mix languages, better security, support for
   version control, and a clean way for software components to interact.
       The opposite of managed code is unmanaged code. Unmanaged code does not execute
   under the Common Language Runtime. Thus, all Windows programs prior to the creation of
   the .NET Framework use unmanaged code. It is possible for managed code and unmanaged
   code to work together, so the fact that C# generates managed code does not restrict its ability
   to operate in conjunction with preexisting programs.

   The Common Language Specification
   Although all managed code gains the benefits provided by the CLR, if your code will be
   used by other programs written in different languages, then for maximum usability, it should
   adhere to the Common Language Specification (CLS). The CLS describes a set of features
   that different .NET-compatible languages have in common. CLS compliance is especially
   important when creating software components that will be used by other languages. The
   CLS includes a subset of the Common Type System (CTS). The CTS defines the rules
   concerning data types. Of course, C# supports both the CLS and the CTS.

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