In This Chapter

In this chapter we will take a look at the basic programming terminology and we will write our first C# program. We will familiarize ourselves with programming – what it means and its connection to computers and programming languages.

Briefly, we will review the different stages of software development.

We will introduce the C# language, the .NET platform and the different Microsoft technologies used in software development. We will examine what tools we need to program in C#. We will use the C# language to write our first computer program, compile and run it from the command line as well as from Microsoft Visual Studio integrated development environment. We will review the MSDN Library – the documentation of the .NET Framework. It will help us with our exploration of the features of the platform and the language.

What Does It Mean "To Program"?

Nowadays computers have become irreplaceable. We use them to solve complex problems at the workplace, look for driving directions, have fun and communicate. They have countless applications in the business world, the entertainment industry, telecommunications and finance. It’s not an over­statement to say that computers build the neural system of our contemporary society and it is difficult to imagine its existence without them.

Despite the fact that computers are so wide-spread, few people know how they really work. In reality, it is not the computers, but the programs (the software), which run on them, that matter. It is the software that makes computers valuable to the end-user, allowing for many different types of services that change our lives.

How Do Computers Process Information?

In order to understand what it means to program, we can roughly compare a computer and its operating system to a large factory with all its workshops, warehouses and transportation. This rough comparison makes it easier to imagine the level of complexity present in a contemporary computer. There are many processes running on a computer, and they represent the workshops and production lines in a factory. The hard drive, along with the files on it, and the operating memory (RAM) represent the warehouses, and the different protocols are the transportation systems, which provide the input and output of information.

The different types of products made in a factory come from different workshops. They use raw materials from the warehouses and store the completed goods back in them. The raw materials are transported to the warehouses by the suppliers and the completed product is transported from the warehouses to the outlets. To accomplish this, different types of transportation are used. Raw materials enter the factory, go through different stages of processing and leave the factory transformed into products. Each factory converts the raw materials into a product ready for consumption.

The computer is a machine for information processing. Unlike the factory in our comparison, for the computer, the raw material and the product are the same thing – information. In most cases, the input information is taken from any of the warehouses (files or RAM), to where it has been previously transported. Afterwards, it is processed by one or more processes and it comes out modified as a new product. Web based applications serve as a prime example. They use HTTP to transfer raw materials and products, and information processing usually has to do with extracting content from a database and preparing it for visualization in the form of HTML.

Managing the Computer

The whole process of manufacturing products in a factory has many levels of management. The separate machines and assembly lines have operators, the workshops have managers and the factory as a whole is run by general executives. Every one of them controls processes on a different level. The machine operators serve on the lowest level – they control the machines with buttons and levers. The next level is reserved for the workshop managers. And on the highest level, the general executives manage the different aspects of the manufacturing processes in the factory. They do that by issuing orders.

It is the same with computers and software – they have many levels of management and control. The lowest level is managed by the processor and its registries (this is accomplished by using machine programs at a low level) – we can compare it to controlling the machines in the workshops. The different responsibilities of the operating system (Windows 7 for example), like the file system, peripheral devices, users and communication protocols, are controlled at a higher level – we can compare it to the management of the different workshops and departments in the factory. At the highest level, we can find the application software. It runs a whole ensemble of processes, which require a huge amount of processor operations. This is the level of the general executives, who run the whole factory in order to maximize the utilization of the resources and to produce quality results.

The Essence of Programming

The essence of programming is to control the work of the computer on all levels. This is done with the help of "orders" and "commands" from the programmer, also known as programming instructions. To "program" means to organize the work of the computer through sequences of instructions. These commands (instructions) are given in written form and are implicitly followed by the computer (respectively by the operating system, the CPU and the peripheral devices).

To “program” means writing sequences of instructions in order to organize the work of the computer to perform something. These sequences of instructions are called “computer programs” or “scripts”.

A sequence of steps to achieve, complete some work or obtain some result is called an algorithm. This is how programming is related to algorithms. Programming involves describing what you want the computer to do by a sequence of steps, by algorithms.

Programmers are the people who create these instructions, which control computers. These instructions are called programs. Numerous programs exist, and they are created using different kinds of programming languages. Each language is oriented towards controlling the computer on a different level. There are languages oriented towards the machine level (the lowest) – Assembler for example. Others are most useful at the system level (interacting with the operating system), like C. There are also high level languages used to create application programs. Such languages include C#, Java, C++, PHP, Visual Basic, Python, Ruby, Perl, JavaScript and others.

In this book we will take a look at the C# programming language – a modern high level language. When a programmer uses C#, he gives commands in high level, like from the position of a general executive in a factory. The instructions given in the form of programs written in C# can access and control almost all computer resources directly or via the operating system. Before we learn how to write simple C# programs, let’s take a good look at the different stages of software development, because programming, despite being the most important stage, is not the only one.

Stages in Software Development

Writing software can be a very complex and time-consuming task, involving a whole team of software engineers and other specialists. As a result, many methods and practices, which make the life of programmers easier, have emerged. All they have in common is that the development of each software product goes through several different stages:

-              Gathering the requirements for the product and creating a task;

-              Planning and preparing the architecture and design;

-              Implementation (includes the writing of program code);

-              Product trials (testing);

-              Deployment and exploitation;

-              Support.

Implementation, testing, deployment and support are mostly accomplished using programming.

Gathering the Requirements

In the beginning, only the idea for a certain product exists. It includes a list of requirements, which define actions by the user and the computer. In the general case, these actions make already existing activities easier – calculating salaries, calculating ballistic trajectories or searching for the shortest route on Google maps are some examples. In many cases the software implements a previously nonexistent functionality such as automation of a certain activity.

The requirements for the product are usually defined in the form of documentation, written in English or any other language. There is no programming done at this stage. The requirements are defined by experts, who are familiar with the problems in a certain field. They can also write them up in such a way that they are easy to understand by the programmers. In the general case, these experts are not programming specialists, and they are called business analysts.

Planning and Preparing the Architecture and Design

After all the requirements have been gathered comes the planning stage. At this stage, a technical plan for the implementation of the project is created, describing the platforms, technologies and the initial architecture (design) of the program. This step includes a fair amount of creative work, which is done by software engineers with a lot of experience. They are sometimes called software architects. According to the requirements, the following parts are chosen:

-              The type of the application – for example console application, desktop application (GUI, Graphical User Interface application), client-server application, Web application, Rich Internet Application (RIA), mobile application, peer-to-peer application or other;

-              The architecture of the software – for example single layer, double layer, triple layer, multi-layer or SOA architecture;

-              The programming language most suitable for the implementation – for example C#, Java, PHP, Python, Ruby, JavaScript or C++, or a combination of different languages;

-              The technologies that will be used: platform (Microsoft .NET, Java EE, LAMP or another), database server (Oracle, SQL Server, MySQL, NoSQL database or another), technologies for the user interface (Flash, JavaServer Faces, Eclipse RCP, ASP.NET, Windows Forms, Silverlight, WPF or another), technologies for data access (for example Hibernate, JPA or ADO.NET Entity Framework), reporting technologies (SQL Server Reporting Services, Jasper Reports or another) and many other combinations of technologies that will be used for the implementation of the various parts of the software system.

-              The development frameworks that will simplify the development, e.g. ASP.NET MVC (for .NET), Knockout.js (for JavaScript), Rails (for Ruby), Django (for Python) and many others.

-              The number and skills of the people who will be part of the development team (big and serious projects are done by large and experienced teams of developers);

-              The development plan – separating the functionality in stages, resources and deadlines for each stage.

-              Others (size of the team, locality of the team, methods of communication etc.).

Although there are many rules facilitating the correct analysis and planning, a fair amount of intuition and insight is required at this stage. This step predetermines the further advancement of the development process. There is no programming done at this stage, only preparation.

Implementation

The stage, most closely connected with programming, is the implementation stage. At this phase, the program (application) is implemented (written) according to the given task, design and architecture. Programmers participate by writing the program (source) code. The other stages can either be short or completely skipped when creating a small project, but the implementation always presents; otherwise the process is not software development. This book is dedicated mainly to describing the skills used during implementation – creating a programmer’s mindset and building the knowledge to use all the resources provided by the C# language and the .NET platform, in order to create software applications.

Product Testing

Product testing is a very important stage of software development. Its purpose is to make sure that all the requirements are strictly followed and covered. This process can be implemented manually, but the preferred way to do it is by automated tests. These tests are small programs, which automate the trials as much as possible. There are parts of the functionality that are very hard to automate, which is why product trials include automated as well as manual procedures to ensure the quality of the code.

The testing (trials) process is implemented by quality assurance engineers (QAs). They work closely with the programmers to find and correct errors (bugs) in the software. At this stage, it is a priority to find defects in the code and almost no new code is written.

Many defects and errors are usually found during the testing stage and the program is sent back to the implantation stage. These two stages are very closely tied and it is common for a software product to switch between them many times before it covers all the requirements and is ready for the deployment and usage stages.

Deployment and Operation

Deployment is the process which puts a given software product into exploitation. If the product is complex and serves many people, this process can be the slowest and most expensive one. For smaller programs this is a relatively quick and painless process. In the most common case, a special program, called installer, is developed. It ensures the quick and easy installation of the product. If the product is to be deployed at a large corporation with tens of thousands of copies, additional supporting software is developed just for the deployment. After the deployment is successfully completed, the product is ready for operation. The next step is to train employees to use it.

An example would be the deployment of a new version of Microsoft Windows in the state administration. This includes installation and configuration of the software as well as training employees how to use it.

The deployment is usually done by the team who has worked on the software or by trained deployment specialists. They can be system administrators, database administrators (DBA), system engineers, specialized consultants and others. At this stage, almost no new code is written but the existing code is tweaked and configured until it covers all the specific requirements for a successful deployment.

Technical Support

During the exploitation process, it is inevitable that problems will appear. They may be caused by many factors – errors in the software, incorrect usage or faulty configuration, but most problems occur when the users change their requirements. As a result of these problems, the software loses its abilities to solve the business task it was created for. This requires additional involvement by the developers and the support experts. The support process usually continues throughout the whole life-cycle of the software product, regardless of how good it is.

The support is carried out by the development team and by specially trained support experts. Depending on the changes made, many different people may be involved in the process – business analysts, architects, programmers, QA engineers, administrators and others.

For example, if we take a look at a software program that calculates salaries, it will need to be updated every time the tax legislation, which concerns the serviced accounting process, is changed. The support team’s intervention will be needed if, for example, the hardware of the end user is changed because the software will have to be installed and configured again.

Documentation

The documentation stage is not a separate stage but accompanies all the other stages. Documentation is an important part of software development and aims to pass knowledge between the different participants in the development and support of a software product. Information is passed along between different stages as well as within a single stage. The development documentation is usually created by the developers (architects, program­mers, QA engineers and others) and represents a combination of documents.

Software Development Is More than Just Coding

As we saw, software development is much more than just coding (writing code), and it includes a number of other processes such as: requirements analysis, design, planning, testing and support, which require a wide variety of specialists called software engineers. Programming is just a small, but very essential part of software development.

In this book we will focus solely on programming, because it is the only process, of the above, without which, we cannot develop software.

Our First C# Program

Before we continue with an in depth description of the C# language and the .NET platform, let’s take a look at a simple example, illustrating how a program written in C# looks like:

class HelloCSharp {   static void Main(string[] args)   {       System.Console.WriteLine("Hello C#!");   } }

The only thing this program does is to print the message "Hello, C#!" on the default output. It is still early to execute it, which is why we will only take a look at its structure. Later we will describe in full how to compile and run a given program from the command prompt as well as from a development environment.

How Does Our First C# Program Work?

Our first program consists of three logical parts:

-              Definition of a class HelloCSharp;

-              Definition of a method Main();

-              Contents of the method Main().

Defining a Class

On the first line of our program we define a class called HelloCSharp. The simplest definition of a class consists of the keyword class, followed by its name. In our case the name of the class is HelloCSharp. The content of the class is located in a block of program lines, surrounded by curly brackets: {}.

Defining the Main() Method

On the third line we define a method with the name Main(), which is the starting point for our program. Every program written in C# starts from a Main() method with the following title (signature):

static void Main(string[] args)

The method must be declared as shown above, it must be static and void, it must have a name Main and as a list of parameters it must have only one parameter of type array of string. In our example the parameter is called args but that is not mandatory. This parameter is not used in most cases so it can be omitted (it is optional). In that case the entry point of the program can be simplified and will look like this:

static void Main()

If any of the aforementioned requirements is not met, the program will compile but it will not start because the starting point is not defined correctly.

Contents of the Main() Method

The content of every method is found after its signature, surrounded by opening and closing curly brackets. On the next line of our sample program we use the system object System.Console and its method WriteLine() to print a message on the default output (the console), in this case "Hello, C#!".

In the Main() method we can write a random sequence of expressions and they will be executed in the order we assigned to them.

More information about expressions can be found in chapter "Operators and Expressions", working with the console is described in chapter "Console Input and Output", classes and methods can be found in chapter "Defining Classes".

C# Distinguishes between Uppercase and Lowercase!

The C# language distinguishes between uppercase and lowercase letters so we should use the correct casing when we write C# code. In the example above we used some keywords like class, static, void and the names of some of the system classes and objects, such as System.Console.

Be careful when writing! The same thing, written in upper-case, lower-case or a mix of both, means different things in C#. Writing Class is different from class and System.Console is different from SYSTEM.CONSOLE.

This rule applies to all elements of your program: keywords, names of variables, class names etc.

The Program Code Must Be Correctly Formatted

Formatting is adding characters such as spaces, tabs and new lines, which are insignificant to the compiler and they give the code a logical structure and make it easier to read. Let’s for example take a look at our first program (the short version of the Main() method):

class HelloCSharp {       static void Main()       {             System.Console.WriteLine("Hello C#!");       } }

The program contains seven lines of code and some of them are indented more than others. All of that can be written without tabs as well, like so:

class HelloCSharp { static void Main() { System.Console.WriteLine("Hello C#!"); } }

Or on the same line:

class HelloCSharp{static void Main(){System.Console.WriteLine( "Hello C#!");}}

Or even like this:

class     HelloCSharp {     static void                             Main()     {                             System         . Console.WriteLine("Hello C#!")       ;}          }

The examples above will compile and run exactly like the formatted code but they are more difficult to read and understand, and therefore difficult to modify and maintain.

Never let your programs contain unformatted code! That severely reduces program readability and leads to difficulties for later modifications of the code.

Main Formatting Rules

If we want our code to be correctly formatted, we must follow several important rules regarding indentation:

-      Methods are indented inside the definition of the class (move to the right by one or more [Tab] characters);

-      Method contents are indented inside the definition of the method;

-      The opening curly bracket { must be on its own line and placed exactly under the method or class it refers to;

-      The closing curly bracket } must be on its own line, placed exactly vertically under the respective opening bracket (with the same indentation);

-      All class names must start with a capital letter;

-      Variable names must begin with a lower-case letter;

-      Method names must start with a capital letter;

Code indentation follows a very simple rule: when some piece of code is logically inside another piece of code, it is indented (moved) on the right with a single [Tab]. For example if a method is defined inside a class, it is indented (moved to the right). In the same way if a method body is inside a method, it is indented. To simplify this, we can assume that when we have the character “{“, all the code after it until its closing “}” should be indented on the right.

File Names Correspond to Class Names

Every C# program consists of one or several class definitions. It is accepted that each class is defined in a separate file with a name corresponding to the class name and a .cs extension. When these requirements are not met, the program will still work but navigating the code will be difficult. In our example, the class is named HelloCSharp, and as a result we must save its source code in a file called HelloCSharp.cs.

The C# Language and the .NET Platform

The first version of C# was developed by Microsoft between 1999 and 2002 and was officially released to the public in 2002 as a part of the .NET platform. The .NET platform aims to make software development for Windows easier by providing a new quality approach to programming, based on the concepts of the "virtual machine" and "managed code". At that time the Java language and platform reaped an enormous success in all fields of software development; C# and .NET were Microsoft’s natural response to the Java technology.

The C# Language

C# is a modern, general-purpose, object-oriented, high-level prog­ramming language. Its syntax is similar to that of C and C++ but many features of those languages are not supported in C# in order to simplify the language, which makes programming easier.

The C# programs consist of one or several files with a .cs extension, which contain definitions of classes and other types. These files are compiled by the C# compiler (csc) to executable code and as a result assemblies are created, which are files with the same name but with a different extension (.exe or .dll). For example, if we compile HelloCSharp.cs, we will get a file with the name HelloCSharp.exe (some additional files will be created as well, but we will not discuss them at the moment).

We can run the compiled code like any other program on our computer (by double clicking it). If we try to execute the compiled C# code (for example HelloCSharp.exe) on a computer that does not have the .NET Framework, we will receive an error message.

Keywords

C# uses the following keywords to build its programming constructs (the list is taken from MSDN in March 2013 and may not be complete):

abstract	as	base	bool	break	byte
case	catch	char	checked	class	const
continue	decimal	default	delegate	do	double
else	enum	event	explicit	extern	false
finally	fixed	float	for	foreach	goto
if	implicit	in	int	interface	internal
is	lock	long	namespace	new	null
object	operator	out	override	params	private
protected	public	readonly	ref	return	sbyte
sealed	short	sizeof	stackalloc	static	string
struct	switch	this	throw	true	try
typeof	uint	ulong	unchecked	unsafe	ushort
using	virtual	void	volatile	while

Since the creation of the first version of the C# language, not all keywords are in use. Some of them were added in later versions. The main program elements in C# (which are defined and used with the help of keywords) are classes, methods, operators, expressions, conditional statements, loops, data types, exceptions and few others. In the next few chapters of this book, we will review in details all these programming constructs along with the use of the most of the keywords from the table above.

Automatic Memory Management

One of the biggest advantages of the .NET Framework is the built-in automatic memory management. It protects the programmers from the complex task of manually allocating memory for objects and then waiting for a suitable moment to release it. This significantly increases the developer productivity and the quality of the programs written in C#.

In the .NET Framework, there is a special component of the CLR that looks after memory management. It is called a "garbage collector" (automated memory cleaning system). The garbage collector has the following main tasks: to check when the allocated memory for variables is no longer in use, to release it and make it available for allocation of new objects.

It is important to note that it is not exactly clear at what moment the memory gets cleaned of unused objects (local variables for example). According to the C# language specifications, it happens at some moment after a given variable gets out of scope but it is not specified, whether this happens instantly, after some time or when the available memory becomes insufficient for the normal program operation.

Independence from the Environment and the Programming Language

One of the advantages of .NET is that programmers using different .NET languages can easily exchange their code. For example a C# programmer can use the code written by another programmer in VB.NET, Managed C++ or F#. This is possible because the programs written in different .NET languages share a common system of data types, execution infrastructure and a unified format of the compiled code (assemblies).

A big advantage of the .NET technology is the ability to run code, which is written and compiled only once, on different operating systems and hardware devices. We can compile a C# program in a Windows environment and then execute it under Windows, Windows Mobile, Windows RT or Linux. Officially Microsoft only supports the .NET Framework on Windows, Windows Mobile and Windows Phone, but there are third party vendors that offer .NET implementation on other operating systems.

Mono (.NET for Linux)

One example of .NET implementation for non-Windows environment is the open-source project Mono (www.mono-project.com). It implements the .NET Framework and most of its accompanying libraries for Linux, FreeBSD, iPhone and Android. Mono is unofficial .NET implementation and some features may work not exactly as expected. It does implement well the core .NET standards (such as C# compiler and CLR) but does not support fully the latest .NET technologies and framework like WPF and ASP.NET MVC.

Microsoft Intermediate Language (MSIL)

The idea for independence from the environment has been set in the earliest stages of creation of the .NET platform and is implemented with the help of a little trick. The output code is not compiled to instructions for a specific microprocessor and does not use the features of a specific operating system; it is compiled to the so called Microsoft Intermediate Language (MSIL). This MSIL is not directly executed by the microprocessor but from a virtual environment called Common Language Runtime (CLR).

Common Language Runtime (CLR) – the Heart of .NET

In the very center of the .NET platform beats its heart – the Common Language Runtime (CLR) – the environment that controls the execution of the managed code (MSIL code). It ensures the execution of .NET programs on different hardware platforms and operating systems.

CLR is an abstract computing machine (virtual machine). Similarly to physical computers, it supports a set of instructions, registries, memory access and input-output operations. CLR ensures a controlled execution of the .NET programs using the full capabilities of the processor and the operating system. CLR also carries out the managed access to the memory and the other resources of the computer, while adhering to the access rules set when the program is executed.

The .NET Platform

The .NET platform contains the C# language, CLR and many auxiliary instruments and libraries ready for use. There are a few versions of .NET according to the targeted user group:

-      .NET Framework is the most common version of the .NET environment because of its general purpose. It is used in the development of console applications, Windows applications with a graphical user interface, web applications and many more.

-      .NET Compact Framework (CF) is a "light" version of the standard .NET Framework and is used in the development of applications for mobile phones and other PDA devices using Windows Mobile Edition.

-      Silverlight is also a "light" version of the .NET Framework, intended to be executed on web browsers in order to implement multimedia and Rich Internet Applications.

-      .NET for Windows Store apps is a subset of .NET Framework designed for development and execution of .NET applications in Windows 8 and Windows RT environment (the so called Windows Store Apps).

.NET Framework

The standard version of the .NET platform is intended for development and use of console applications, desktop applications, Web applications, Web services, Rich Internet Applications, mobile applications for tablets and smart phones and many more. Almost all .NET developers use the standard version.

.NET Technologies

Although the .NET platform is big and comprehensive, it does not provide all the tools required to solve every problem in software development. There are many independent software developers, who expand and add to the standard functionality offered by the .NET Framework. For example, companies like the Bulgarian software corporation Telerik develop subsidiary sets of components. These components are used to create graphical user interfaces, Web content management systems, to prepare reports and they make application development easier.

The .NET Framework extensions are software components, which can be reused when developing .NET programs. Reusing code significantly facilitates and simplifies software development, because it provides solutions for common problems, offers implementations of complex algorithms and technology standards. The contemporary programmer uses libraries and components every day, and saves a lot of effort by doing so.

Let’s look at the following example – software that visualizes data in the form of charts and diagrams. We can use a library, written in .NET, which draws the charts. All that we need to do is input the correct data and the library will draw the charts for us. It is very convenient and efficient. Also it leads to reduction in the production costs because the programmers will not need to spend time working on additional functionality (in our case drawing the charts, which involves complex mathematical calculations and controlling the graphics card). The application itself will be of higher quality because the extension it uses is developed and supported by specialists with more experience in that specific field.

Software technologies are sets of classes, modules, libraries, programming models, tools, patterns and best practices addressing some specific problem in software development. There are general software technologies, such as Web technologies, mobile technologies, technologies for computer graphics and technologies related to some platform such as .NET or Java.

There are many .NET technologies serving for different areas of .NET development. Typical examples are the Web technologies (like ASP.NET and ASP.NET MVC), allowing fast and easy creation of dynamic Web applications and .NET mobile technologies (like WinJS), which make possible the creation of rich user interface multimedia applications working on the Internet.

.NET Framework by default includes as part of itself many technologies and class libraries with standard functionality, which developers can use. For example, there are ready-to-use classes in the system library working with mathematical functions, calculating logarithms and trigonometric functions (System.Math class). Another example is the library dealing with networks (System.Net), it has a built-in functionality to send e-mails (using the System.Net.Mail.MailMessage class) and to download files from the Internet (using System.Net.WebClient).

A .NET technology is the collection of .NET classes, libraries, tools, standards and other programming means and established development models, which determine the technological framework for creating a certain type of application. A .NET library is a collection of .NET classes, which offer certain ready-to-use functionality. For example, ADO.NET is a technology offering standardized approach to accessing relational databases (like Microsoft SQL Server and MySQL). The classes in the package (namespace) System.Data.SqlClient are an example of .NET library, which provide functionality to connect an SQL Server through the ADO.NET technology.

Some of the technologies developed by software developers outside of Microsoft become wide-spread and as a result establish themselves as technology standards. Some of them are noticed by Microsoft and later are added to the next iteration of the .NET Framework. That way, the .NET platform is constantly evolving and expanding with new libraries and technologies. For instance, the object-relational mapping technologies initially were developed as independent projects and products (like the open code project NHibernate and Telerik’s OpenAccess ORM). After they gained enormous popularity, their inclusion in the .NET Framework became a necessity. And this is how the LINQ-to-SQL and ADO.NET Entity Framework technologies were born, respectively in .NET 3.5 and .NET 4.0.

Application Programming Interface (API)

Each .NET library or technology is utilized by creating objects and calling their methods. The set of public classes and methods in the programming libraries is called Application Programming Interface or just API. As an example we can look at the .NET API itself; it is a set of .NET class libraries, expanding the capabilities of the language and adding high-level functionality. All .NET technologies offer a public API. The technologies are often referred to simply as API, which adds certain functionality. For example: API for working with files, API for working with charts, API for working with printers, API for reading and creating Word and Excel documents, API for creating PDF documents, Web development API, etc.

.NET Documentation

Very often it is necessary to document an API, because it contains many namespaces and classes. Classes contain methods and parameters. Their purpose is not always obvious and needs to be explained. There are also inner dependencies between the separate classes, which need to be explained in order to be used correctly. These explanations and technical instructions on how to use a given technology, library or API, are called documentation. The documentation consists of a collection of documents with technical content.

The .NET Framework also has a documentation officially developed and supported by Microsoft. It is publicly available on the Internet and is also distributed with the .NET platform as a collection of documents and tools for browsing and searching.

The MSDN Library is Microsoft’s official documentation for all their products for developers and software technologies. The .NET Framework’s technical documentation is part of the MSDN Library and can be found here: http://msdn.microsoft.com/en-us/library/vstudio/gg145045.aspx. The above screenshot shows how it might look like (for .NET version 4.5).

What We Need to Program in C#?

After we made ourselves familiar with the .NET platform, .NET libraries and .NET technologies, we can move on to writing, compiling and executing C# programs.

In order to program in C#, we need two basic things – an installed .NET Framework and a text editor. We need the text editor to write and edit the C# code and the .NET Framework to compile and execute it.

.NET Framework

By default, the .NET Framework is installed along with Windows, but in old Windows versions it could be missing. To install the .NET Framework, we must download it from Microsoft’s website (http://download.microsoft.com). It is best if we download and install the latest version.

Do not forget that we need to install the .NET Framework before we begin! Otherwise, we will not be able to compile and execute the program. If we run Windows 8 or Windows 7, the .NET Framework will be already installed as part of Windows.

Text Editor

The text editor is used to write the source code of the program and to save it in a file. After that, the code is compiled and executed. There are many text editing programs. We can use Windows’ built-in Notepad (it is very basic and inconvenient) or a better free text editor like Notepad++ (notepad-plus.sourceforge.net) or PSPad (www.pspad.com).

Compilation and Execution of C# Programs

The time has come to compile and execute the simple example program written in C# we already discussed. To accomplish that, we need to do the following:

-              Create a file named HelloCSharp.cs;

-              Write the sample program in the file;

-              Compile HelloCSharp.cs to an executable file HelloCSharp.exe using the console-based C# compiler (csc.exe);

-              Execute the HelloCSharp.exe file.

Now, let’s do it on the computer!

The instructions above vary depending on the operating system. Since programming on Linux is not the focus of this book, we will take a thorough look at what we need to write and execute the sample program on Windows. For those of you, who want to program in C# in a Linux environment, we already explained the Mono project, and you can download it and experiment.

Here is the code of our first C# program:

HelloCSharp.cs

class HelloCSharp {       static void Main()       {             System.Console.WriteLine("Hello C#!");       } }

Creating C# Programs in the Windows Console

First we start the Windows command console, also known as Command Prompt. In Windows 7 this is done from the Windows Explorer start menu: Start -> Programs -> Accessories -> Command Prompt.

It is advised that we run the console as administrator (right click on the Command Prompt icon and choose “Run as administrator”). Otherwise some operations we want to use may be restricted.

In Windows 8 the “Run as administrator” command is directly available when you right click the command prompt icon from the Win8 Start Screen:

After opening the console, let’s create a directory, in which we will experiment. We use the md command to create a directory and cd command to navigate to it (enter inside it):

The directory will be named IntroCSharp and will be located in C:\. We change the current directory to C:\IntroCSharp and create a new file HelloCSharp.cs, by using the built-in Windows text editor – Notepad.

To create the text file “HelloCSharp.cs”, we execute the following command on the console:

notepad HelloCSharp.cs

This will start Notepad with the following dialog window, confirming the creation of a new file:

Notepad will warn us that no such file exists and will ask us if we want to create it. We click [Yes]. The next step is to rewrite or simply Copy / Paste the program’s source code.

We save it by pressing [Ctrl+S] and close the Notepad editor with [Alt+F4]. Now we have the initial code of our sample C# program, written in the file C:\IntroCSharp\HelloCSharp.cs.

Compiling C# Programs in Windows

The only thing left to do is to compile and execute it. Compiling is done by the csc.exe compiler.

We got our first error – Windows cannot find an executable file or command with the name "csc". This is a very common problem and it is normal to appear if it is our first time using C#. Several reasons might have caused it:

-              The .NET Framework is not installed;

-              The .NET Framework is installed correctly, but its directory Microsoft.NET\Framework\v4.0.xxx is not added to the system path for executable files and Windows cannot find csc.exe.

The first problem is easily solved by installing the .NET Framework (in our case – version 4.5). The other problem can be solved by changing the system path (we will do this later) or by using the full path to csc.exe, as it is shown on the figure below. In our case, the full file path to the C# compiler is C:\Windows\Microsoft.NET\Framework\v4.0.30319\csc.exe (note that this path could vary depending on the .NET framework version installed). Strange or not, .NET 4.5 coming with Visual Studio 2012 and C# 5 installs in a directory named “v4.0.30319” – this is not a mistake.

Compiling and Running C# Programs in Windows

Now let’s invoke the csc compiler through its full path and pass to it the file we want to compile as a parameter (HelloCSharp.exe):

After the execution csc is completed without any errors, and we get the following file as a result: C:\IntroCSharp\HelloCSharp.exe. To run it, we simply need to write its name. The result of the execution of our program is the message "Hello, C#!" printed on the console. It is not great but it is a good start:

Changing the System Paths in Windows

If we know to use the command line C# compiler (csc.exe) without entering the full path to it, we could add its folder to the Windows system path.

1.   We open Control Panel and select "System". As a result this well-known window appears (the screenshot is taken from Windows 7):

                   In Windows 8 it might look a bit different, but is almost the same:

2.   We select "Advanced system settings". The dialog window "System Properties" appears:

3.   We click the button "Environment Variables" and a window with all the environment variables shows up:

4.   We choose "Path" from the list of System variables, as shown on the figure, and press the "Edit" button. A small window appears, in which we enter the path to the directory where the .NET Framework is installed:

Of course, first we need to find where our .NET Framework is installed. By default it is located somewhere inside the Windows system directory C:\Windows\Microsoft.NET, for example:

C:\Windows\Microsoft.NET\Framework64\v4.0.30319

Adding the additional path to the already existing ones in the Path variable of the environment is done by adjoining the path name to the others and using a semicolon (;) as a spacer.

We must be careful because if we delete any of the existing system paths, some of Windows’ functions or part of the installed software might fail to operate properly!

5.   When we are done with setting the path, we can try running csc.exe, without entering its full path. To do so, we open a new cmd.exe (Command Prompt) window (it is important to restart the Command Prompt) and type in the "csc" command. We should see the C# compiler version and a message that no input file has been specified: