Wiley Beginning Visual C# 2005
Contents
1. Assembly When this code is executed either in its own right if it is an executable or when it is used from other code it must first be compiled into native code using a JIT compiler as shown in Figure 1 3 Assembly l JIT Connon gt l Figure 1 3 C application code Figure 1 2 The native code is executed in the context of the managed CLR along with any other running applications or processes as shown in Figure 1 4 System Runtime NET CLR aa ee ee 41 Native Code Native Code oe 2 L 7 L 7 Figure 1 4 Chapter 1 Linking There is one additional point to note concerning the preceding process The C code that compiles into MSIL in step 2 needn t be contained in a single file It is possible to split application code across multiple source code files which are then compiled together into a single assembly This process is known as link ing and is extremely useful The reason for this is that it is far easier to work with several smaller files than one enormous one You can separate out logically related code into an individual file so that it can be worked on independently and then practically forgotten about when completed This also makes it much easier to locate specific pieces of code when you need them and enables teams of developers to divide up the programming burden into manageable chunks where indivi2. C as well as C Visual Basic JScript and even older languages such as COBOL For this to work NET specific versions of these languages have also appeared and more are being released all the time Not only do all of these have access to the NET Framework but they can also communicate with each other It is perfectly possible for C developers to make use of code written by Visual Basic programmers and vice versa All of this provides a hitherto unthinkable level of versatility and is part of what makes using the NET Framework such an attractive prospect What s in the NET Framework The NET Framework consists primarily of a gigantic library of code that you use from your client lan guages such as C using object oriented programming OOP techniques This library is categorized into different modules you use portions of it depending on the results you want to achieve For exam ple one module contains the building blocks for Windows applications another for network program ming and another for Web development Some modules are divided into more specific submodules such as a module for building Web services within the module for Web development The intention here is for different operating systems to support some or all of these modules depending on their characteristics A PDA for example would include support for all the core NET functionality but is unlikely to require some of the more esoteric modules Part of t
3. and JIT When you compile code that uses the NET Framework library you don t immediately create operating system specific native code Instead you compile your code into Microsoft Intermediate Language MSIL code This code isn t specific to any operating system and isn t specific to C Other NET languages for example Visual Basic NET also compile to this language as a first stage This compilation step is carried out by VS when you use it to develop C applications Obviously to execute an application more work is necessary This is the job of a Just in Time JIT com piler which compiles MSIL into native code that is specific to the OS and machine architecture being targeted Only at this point can the OS execute the application The just in time part of the name here reflects the fact that MSIL code is only compiled as and when it is needed In the past it was often necessary to compile your code into several applications each of which targeted a specific operating system and CPU architecture Often this was a form of optimization to get code to run faster on an AMD chipset for example but at times it was critical for applications to work in both Win9x and WinNT 2000 environments for example This is now unnecessary because JIT compilers as their name suggests use MSIL code which is independent of the machine operating system and CPU Several JIT compilers exist each targeting a different architecture and the
4. line compiler that is part of the NET Framework However why do this when you have the full power of VS to help you Chapter 1 The following is a quick list of some of the features of VS that make it an appealing choice for NET development m m VS automates the steps required to compile source code but at the same time gives you com plete control over any options used should you wish to override them The VS text editor is tailored to the languages VS supports including C so that it can intelli gently detect errors and suggest code where appropriate as you are typing VS includes designers for Windows Forms and Web Forms applications allowing simple drag and drop design of UI elements Many of the types of project possible in C may be created with boilerplate code already in place Instead of starting from scratch you will often find that various code files are started off for you reducing the amount of time spent getting started on a project This is especially true of the new Starter Kit project type which allows you to develop from a fully functional applica tion base Some starter kits are included with the VS installation and you can find plenty more online to play with VS includes several wizards that automate common tasks many of which can add appropriate code to existing files without you having to worry about or even in some cases remember the correct syntax VS contains many powerfu
5. you won t necessarily want to include everything required to run an application in one place You might write some code that performs tasks required by multiple applications In situations like this it is often useful to place this reusable code in a place accessible to all applications In the NET Framework this is the Global Assembly Cache GAC Placing code in this cache is simple you just place the assembly containing the code in the directory containing this cache Managed Code The role of the CLR doesn t end once you have compiled your code to MSIL and a JIT compiler has compiled this to native code Code written using the NET Framework is managed when it is executed this stage is usually referred to as being at runtime This means that the CLR looks after your applica tions by managing memory handling security allowing cross language debugging and so on By con trast applications that do not run under the control of the CLR are said to be unmanaged and certain languages such as C can be used to write such applications that for example access low level func tions of the operating system However in C you can write only code that runs in a managed environ ment You will make use of the managed features of the CLR and allow NET itself to handle any interaction with the operating system Garbage Collection One of the most important features of managed code is the concept of garbage collection This is the NET method
6. Introducing C Welcome to the first chapter of the first section of this book Over the course of this section you look at the basic knowledge required to get up and running with C In this first chapter you get an overview of C and the NET Framework and you consider what these technologies are the motivation for using them and how they relate to each other You start with a general discussion of the NET Framework This is still a new technology and con tains many concepts that are tricky to come to grips with at first mainly because the Framework introduces a new way of doing things to application development This means that the discussion will by necessity cover many new concepts in a short space of time However a quick look at the basics is essential to understand how to program in C so this is a necessary evil Later in the book you will revisit many of the topics covered here in more detail After this general discussion you move on to a simple description of C itself including its origins and similarities to C Finally you look at the primary tool used throughout this book Visual Studio 2005 VS In this chapter you learn OQ What C and the NET Framework are Q How the NET Framework works and what makes it special Q What you can do with C Q What Visual Studio 2005 is and how it fits in with this book What Is the NET Framework The NET Framework is a new and revolutionary platform created by Microsoft fo
7. appropriate one will be used to create the native code required The beauty of all this is that it requires a lot less work on your part in fact you can just forget about system dependent details and concentrate on the more interesting functionality of your code Assemblies When you compile an application the MSIL code created is stored in an assembly Assemblies include both executable application files that you can run directly from Windows without the need for any other programs these have a exe file extension and libraries for use by other applications which have a d11 extension As well as containing MSIL assemblies also contain meta information that is information about the information contained in the assembly also known as metadata and optional resources additional data used by the MSIL such as sound files and pictures The meta information allows assemblies to be fully Chapter 1 self descriptive You need no other information to use an assembly meaning that you avoid situations such as failing to add required data to the system registry and so on which was often a problem when developing with other platforms This means that deploying applications is often as simple as copying the files into a directory on a remote computer Since no additional information is required on the target systems you can just run an executable file from this directory and assuming the NET CLR is installed away you go Of course
8. duals can check out pieces of code to work on without risking damage to otherwise satisfactory sections or sections that other peo ple are working on What Is C C as mentioned earlier is one of the languages that can be used to create applications that will run in the NET CLR It is an evolution of the C and C languages and has been created by Microsoft specifi cally to work with the NET platform Because it is a recent development the C language has been designed with hindsight taking into account many of the best features from other languages while clearing up their problems Developing applications using C is simpler than using C because the language syntax is simpler However C is a powerful language and there is little you might want to do in C that you can t do in C Having said that those features of C that parallel the more advanced features of C such as directly accessing and manipulating system memory can only be carried out using code marked as unsafe This advanced programmatic technique is potentially dangerous hence its name because it is possible to overwrite system critical blocks of memory with potentially catastrophic results For this rea son and others this book will not cover this topic At times C code is slightly more verbose than C This is a consequence of C being a type safe lan guage unlike C In layperson s terms this means that once some data has been assigned to a
9. effectively namely a development environment such as Visual Studio 2005 In the next chapter you get some C code running using VS which will give you enough knowledge to sit back and concentrate on the C language itself rather than worrying too much about how VS works 11
10. g graphics performing complex mathematical tasks and so on C in This Book The first section of this book deals with the syntax and usage of the C language without too much empha sis on the NET Framework This is necessary because you won t be able to use the NET Framework at all without a firm grounding in C programming You start off even simpler in fact and leave the more involved topic of object oriented programming OOP until you ve covered the basics These will be taught from first principles assuming no programming knowledge at all Once you have done this you will be ready to move on to developing the types of application listed in the last section Section two of this book will look at Windows Forms programming Section three will look at Web application and Web service programming Section four will examine data access for database file system and XML data and Section five covers some other NET topics of interest such as more about assemblies and graphics programming Visual Studio 2005 In this book you use Visual Studio 2005 VS for all of your C development from simple command line applications to the more complex project types considered VS isn t essential for developing C applica tions but it makes things much easier for you You can if you wish to manipulate C source code files in a basic text editor such as the ubiquitous Notepad application and compile code into assemblies using the command
11. he NET Framework library defines some basic types A type is a representation of data and specifying some of the most fundamental of these such as a 32 bit signed integer facilitates interoper ability between languages using the NET Framework This is called the Common Type System CTS As well as supplying this library the Framework also includes the NET Common Language Runtime CLR which is responsible for maintaining the execution of all applications developed using the NET library Introducing C How Do Write Applications Using the NET Framework Writing an application using the NET Framework means writing code using any of the languages that support the Framework using the NET code library In this book you use VS for your development VS is a powerful integrated development environment that supports C as well as managed and unmanaged C Visual Basic and some others The advantage of this environment is the ease with which NET features can be integrated into your code The code that you will create will be entirely C but will use the NET Framework throughout and you make use of the additional tools in VS where necessary In order for C code to execute it must be converted into a language that the target operating system understands known as native code This conversion is called compiling code an act that is performed by a compiler Under the NET Framework however this is a two stage process MSIL
12. l tools for visualizing and navigating through elements of your projects whether they are C source code files or other resources such as bitmap images or sound files As well as simply writing applications in VS it is possible to create deployment projects mak ing it easy to supply code to clients and for them to install it without much trouble VS enables you to use advanced debugging techniques when developing projects such as the ability to step through code one instruction at a time while keeping an eye on the state of your application There is much more than this but hopefully you have the idea Visual Studio 2005 Express Products In addition to Visual Studio 2005 Microsoft also supplies several simpler development tools known as Visual Studio 2005 Express Products These are currently at the time of this writing in beta versions but are freely available at http lab msdn microsoft com express Two of these products Visual C 2005 Express and Visual Web Developer 2005 Express together allow you to create almost any C application you d care to mention They both function as cut down versions of VS and retain the same look and feel While they offer many of the same features as VS there are some notable feature absences although not so many that they would prevent you from using them to work through this book VS Solutions When you use VS to develop applications you do so by creating solutions A solution in VS term
13. of making sure that the memory used by an application is freed up completely when the appli cation is no longer in use Prior to NET this has mostly been the responsibility of programmers and a few simple errors in code could result in large blocks of memory mysteriously disappearing as a result of being allocated to the wrong place in memory This usually meant a progressive slowdown of your computer followed by a system crash NET garbage collection works by inspecting the memory of your computer every so often and removing anything from it that is no longer needed There is no set timeframe for this it might happen thousands of times a second once every few seconds or whenever but you can rest assured that it will happen There are some implications for programmers here Since this work is done for you at an unpredictable time applications have to be designed with this in mind Code that requires a lot of memory to run should tidy itself up rather than waiting for garbage collection to happen but this isn t anything like as tricky as it sounds Fitting It Together Before moving on I ll summarize the steps required to create a NET application as discussed previously 1 Application code is written using a NET compatible language such as C as shown in Figure 1 1 3 Introducing C C code Figure 1 1 This code is compiled into MSIL which is stored in an assembly as shown in Figure 1 2 il Compliation gt
14. r developing applications Chapter 1 The most interesting thing about this statement is how vague I ve been but there are good reasons for this For a start note that I didn t say developing applications on the Windows operating system Although the Microsoft release of the NET Framework runs on the Windows operating system it is fast becoming possible to find alternative versions that will work on others One example of this is Mono an open source version of the NET Framework including a C compiler that will run on several operating systems including various flavors of Linux and Mac OS More such projects are in the pipeline and may be available by the time you read this In addition you can use the Microsoft NET Compact Framework essentially a subset of the full NET Framework on personal digital assistant PDA class devices and even some smartphones One of the key motivational forces behind the INET Framework is its intended use as a means of integrating disparate operating systems In addition the definition of the NET Framework given above includes no restriction on the type of applications that are possible This is because there is no restriction the NET Framework allows the creation of Windows applications Web applications Web services and pretty much anything else you can think of The NET Framework has been designed so that it can be used from any language This includes the sub ject of this book
15. s is more than just an application Solutions contain projects which might be Windows Forms projects 10 Introducing C Web Form projects and so on However solutions can contain multiple projects so that you can group together related code in one place even if it will eventually compile to multiple assemblies in various places on your hard disk This is very useful because it allows you to work on shared code which might be placed in the GAC at the same time as applications that use this code Debugging code is a lot easier when only one develop ment environment is used because you can step through instructions in multiple code modules Summary In this chapter you looked at the NET Framework in general terms and discovered how it makes it easy for you to create powerful and versatile applications You saw what is necessary to turn code in languages such as C into working applications and what benefits you gain from using managed code running in the NET Common Language Runtime You also saw what C actually is and how it relates to the NET Framework and you were introduced to the tool that you ll use for C development Visual Studio NET In this chapter you learned Q What the NET Framework is why it was created and what makes it such an attractive environ ment to program in Qh What C is and what makes it an idea tool to program in the NET Framework Q What you need to develop NET applications
16. s no restrictions on the types of applications that are possible as discussed ear lier C uses the Framework and so also has no restrictions on possible applications However here are a few of the more common application types Windows Applications These are applications such as Microsoft Office which have a familiar Windows look and feel about them This is made simple by using the Windows Forms module of the NET Framework which is a library of controls such as buttons toolbars menus and so on that you can use to build a Windows user interface UI Ql Web Applications These are Web pages such as might be viewed through any Web browser The NET Framework includes a powerful system of generating Web content dynamically allowing personalization security and much more This system is called ASP NET Active Server Pages NET and you can use C to create ASP NET applications using Web Forms C1 Web Services These are a new and exciting way of creating versatile distributed applications Using Web services you can exchange virtually any data over the Internet using the same simple syntax regardless of the language used to create a Web service or the system that it resides on Any of these types may also require some form of database access which can be achieved using the ADO NET Active Data Objects NET section of the NET Framework Many other resources can be drawn on such as tools for creating networking components outputtin
17. type it cannot subsequently transform itself into another unrelated type Consequently there are strict rules that must be adhered to when converting between types which means that you will often need to write more code to carry out the same task in C than you might write in C but you get the benefits that code is more robust and debugging is simpler NET can always track what type a piece of data is at any time In C you therefore may not be able to do things such as take the region of memory 4 bytes into this data and 10 bytes long and interpret it as X but that s not necessarily a bad thing C is just one of the languages available for NET development but in my opinion it is certainly the best It has the advantage of being the only language designed from the ground up for the NET Framework and may be the principal language used in versions of NET that are ported to other operating systems To keep languages such as the NET version of Visual Basic as similar as possible to their predecessors yet compliant with the CLR certain features of the NET code library are not fully supported By con trast C is able to make use of every feature that the NET Framework code library has to offer The lat est version of NET includes several improvements to the C language partly in response to requests from developers making it even more powerful Introducing C What Kind of Applications Can I Write with C The NET Framework ha
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