C# Step by Step Codes Essay Example

C# Step by Step Codes Essay SREEKANTH C# STEP BY STEP Microsoft Visual Studio C#. NET Step By Step 1 SREEKANTH C# STEP BY STEP Introduction Microsoft Visual C# is a powerful but simple language aimed primarily at developers creating applications by using the Microsoft . NET Framework. It inherits many of the best features of C++ and Microsoft Visual Basic, but few of the inconsistencies and anachronisms, resulting in a cleaner and more logical language. The advent of C# 2. 0 has seen several important new features added to the language, including Generics, Iterators, and anonymous methods. The development environment provided by Microsoft Visual Studio 2005 makes these powerful features easy to use, and the many new wizards and enhancements included in Visual Studio 2005 can greatly improve your productivity as a developer. The aim of this book is to teach you the fundamentals of programming with C# by using Visual Studio 2005 and the . NET Framework. You will learn the features of the C# language, and then use them to build applications running on the Microsoft Windows operating system. By the time you complete this book, you will have a thorough understanding of C# and will have used it to build Windows Forms applications, access Microsoft SQL Server databases, develop ASP. NET Web applications, and build and consume a Web service. Part I Introducing Microsoft Visual C# and Microsoft Visual Studio 2005 Chapter 1 Welcome to C# After completing this chapter, you will be able to: †¢ †¢ †¢ †¢ Use the Visual Studio 2005 programming environment. Create a C# console application. Use namespaces. Create a C# Windows Forms application. Microsoft Visual C# is Microsofts powerful, component-oriented language. We will write a custom essay sample on C# Step by Step Codes specifically for you for only $16.38 $13.9/page Order now We will write a custom essay sample on C# Step by Step Codes specifically for you FOR ONLY $16.38 $13.9/page Hire Writer We will write a custom essay sample on C# Step by Step Codes specifically for you FOR ONLY $16.38 $13.9/page Hire Writer C# plays an important role in the architecture of the Microsoft . NET Framework, and some people have drawn comparisons to the role that C played in the development of UNIX. If you already know a language such as C, C++, or Java, youll find the syntax of C# reassuringly familiar because it uses the same curly brackets to delimit blocks of code. However, if you are used to programming in other languages, you should soon be able to pick up the syntax and feel of C#; you just need to learn to put the curly brackets and semi-colons in the right place. Hopefully this is just the book to help you! In Part I, youll learn the fundamentals of C#. Youll discover how to declare variables and how to use operators such as plus (+) and minus (-) to create values. Youll see how to write methods and pass arguments to methods. Youll also learn how to use selection statements such as if and iteration statements such as while. Finally, youll understand how C# uses exceptions to handle errors in a graceful, easy-to-use manner. These topics form the core of C#, and from this solid foundation, youll progress to more advanced features in Part II through Part VI. 2 SREEKANTH C# STEP BY STEP Beginning Programming with the Visual Studio 2005 Environment Visual Studio 2005 is a tool-rich programming environment containing all the functionality youll need to create large or small C# projects. You can even create projects that seamlessly combine modules from different languages. In the first exercise, youll start the Visual Studio 2005 programming environment and learn how to create a console application. Create a console application in Visual Studio 2005 1. In Microsoft Windows, click the Start button, point to All Programs, and then point to Microsoft Visual Studio 2005. 2. Click the Microsoft Visual Studio 2005 icon. Visual Studio 2005 starts. NOTE If this is the first time that you have run Visual Studio 2005, you might see a dialog box prompting you to choose your default development environment settings. Visual Studio 2005 can tailor itself according your preferred development language. The various dialog boxes and tools in the integrated development environment (IDE) will have their default selections set for the language you 3 SREEKANTH C# STEP BY STEP choose. Select Visual C# Development Settings from the list, and then click the Start Visual Studio button. After a short delay, the Visual Studio 2005 IDE appears. 3. On the File menu, point to New, and then click Project. The New Project dialog box opens. This dialog box allows you to create a new project using various templates, such as Windows Application, Class Library, and Console Application, that specify the type of application you want to create. NOTE The actual templates available depend on the version of Visual Studio 2005 you are using. It is also possible to define new project templates, but that is beyond the scope of this book. 4. In the Templates pane, click the Console Application icon. 5. In the Location field, type C:Documents and SettingsYourNameMy DocumentsMicrosoft PressVisual CSharp Step by StepChapter 1. Replace the text YourName in this path with your Windows user name. To save a bit of space throughout the rest of this book, we will simply refer to the path â€Å"C:Documents and SettingsYourNameMy Documents† as your â€Å"My Documents† folder. 4 SREEKANTH C# STEP BY STEP NOTE If the folder you specify does not exist, Visual Studio 2005 creates it for you. 6. In the Name field, type TextHello. . Ensure that the Create Directory for Solution check box is checked and then click OK. The new project opens. The menu bar at the top of the screen provides access to the features youll use in the programming environment. You can use the keyboard or the mouse to access the menus and commands exactly as you can in all Windows-based programs. The toolbar is located beneath the menu bar and provides button shortcuts to run the most frequently used commands. The Code and Text Editor window occupying the main part of the IDE displays the contents of source files. In a multi-file project, each source file has its own tab labeled with the name of the source file. You can click the tab once to bring the named source file to the foreground in the Code and Text Editor window. The Solution Explorer displays the names of the files associated with the project, among other items. You can also double-click a file name in the Solution Explorer to bring that source file to the foreground in the Code and Text Editor window. 5 SREEKANTH C# STEP BY STEP Before writing the code, examine the files listed in the Solution Explorer, which Visual Studio 2005 has created as part of your project: Solution TextHello This is the top-level solution file, of which there is one per application. If you use Windows Explorer to look at your My DocumentsVisual CSharp Step by StepChapter 1TextHello folder, youll see that the actual name of this file is TextHello. sln. Each solution file contains references to one or more project files. †¢ TextHello This is the C# projec t file. Each project file references one or more files containing the source code and other items for the project. All the source code in a single project must be written in the same programming language. In Windows Explorer, this file is actually called TextHello. csproj, and it is stored in your My DocumentsVisual CSharp Step by StepChapter 1TextHelloTextHello folder. †¢ Properties This is a folder in the TextHello project. If you expand it, you will see that it contains a file called AssemblyInfo. cs. AssemblyInfo. cs is a special file that you can use to add attributes to a program, such as the name of the author, the date the program was written, and so on. There are additional attributes that you can use to modify the way in which the program will run. These attributes are outside the scope of this book. †¢ References This is a folder that contains references to compiled code that your application can use. When code is compiled, it is converted into an assembly and given a unique name. Developers use assemblies to package up useful bits of code that they have written for distribution to other developers that might want to use them in their applications. Many of the features that you will be using when writing applications using this book will make use of assemblies provided by Microsoft with Visual Studio 2005. †¢ Program. cs This is a C# source file, and is the one displayed in the Code and Text Editor window when the project is first created. You will write your code in this file. It contains some code that Visual Studio 2005 provides automatically, which you will examine shortly. Writing Your First Program The Program. cs file defines a class called Program that contains a method called Main. All methods must be defined inside a class. The Main method is special—it designates the programs entry point. It must be a static method. (Methods are discussed in 6 SREEKANTH C# STEP BY STEP Chapter 3, â€Å"Writing Methods and Applying Scope. Static methods are discussed in Chapter 7, â€Å"Creating and Managing Classes and Objects. † The Main method is discussed in Chapter 11, â€Å"Understanding Parameter Arrays. †) IMPORTANT C# is a case-sensitive language. You must spell Main with a capital M. In the following exercises, youll write the code to display the message Hello World in the co nsole; youll build and run your Hello World console application; youll learn how namespaces are used to partition code elements. Write the code using IntelliSense technology 1. In the Code and Text Editor window displaying the Program. s file, place the cursor in the Main method after the opening brace, and type Console. As you type the letter C at the start of the word Console an IntelliSense list appears. This list contains all of the valid C# keywords and data types that are valid in this context. You can either continue typing, or scroll through the list and double-click the Console item with the mouse. Alternatively, after you have typed Con, the Intellisense list will automatically home in on the Console item and you can press the Tab, Enter, or Spacebar key to select it. Main should look like this: static void Main(string[] args) Console } NOTE Console is a built-in class that contains the methods for displaying messages on the screen and getting input from the keyboard. 2. T ype a period immediately after Console. Another Intellisense list appears displaying the methods, properties, and fields of the Console class. 3. Scroll down through the list until WriteLine is selected, and then press Enter. Alternatively, you can continue typing until WriteLine is selected and then press Enter. The IntelliSense list closes, and the WriteLine method is added to the source file. Main should now look like this: static void Main(string[] args) Console. WriteLine } 4. Type an open parenthesis. Another IntelliSense tip appears. This tip displays the parameters of the WriteLine method. In fact, WriteLine is an overloaded method, meaning that Console contains more than one method named Write Line. Each version of the WriteLine method can be used to output different 7 SREEKANTH C# STEP BY STEP types of data. (Overloaded methods are discussed in Chapter 3. ) Main should now look like this: static void Main(string[] args) { Console. WriteLine( } You can click the tips up and down arrows to scroll through the overloaded versions of WriteLine. . Type a close parenthesis, followed by a semicolon. Main should now look like this: static void Main(string[] args) { Console. WriteLine(); } 6. Type the string Hello World between the left and right parentheses. Main should now look like this: static void Main(string[] args) { Console. WriteLine(Hello World); } TIP Get into the habit of typing matched character pairs, such as ( and ) and { and }, before filling in their contents. Its easy to forget the closing character if you wait until after youve entered the contents. 8 SREEKANTH C# STEP BY STEP NOTE You will frequently see lines of code containing two forward slashes followed by ordinary text. These are comments. They are ignored by the compiler, but are very useful for developers because they help document what a program is actually doing. For example: Console. ReadLine(); // Wait for the user to press the Enter key All text from the two slashes to the end of the line will be skipped by the compiler. You can also add multi-line comments starting with /*. The compiler will skip everything until it finds a */ sequence, which could be many lines lower down. You are actively encouraged to document your code with as many comments as necessary. Build and run the console application 1. On the Build menu, click Build Solution. This action causes the C# code to be compiled, resulting in a program that you can run. The Output windows appears below the Code and Text Editor window. a. TIP If the Output window does not appear, click the View menu, and then click Output to display it. b. In the Output window, messages similar to the following show how the program is being compiled and display the details of any errors that have 9 SREEKANTH C# STEP BY STEP occurred. In this case there should be no errors or warnings, and the program should build successfully: c. Build started: Project: TextHello, Configuration: Debug Any CPU d. Csc. exe /config /nowarn:1701;1702 /errorreport: prompt /warn:4 e. Compile complete –- 0 errors, 0 warnings f. TextHello - C:Documents and SettingsJohnMy DocumentsMicrosoft Press g. ============ Build: 1 succeeded or up-to-date, 0 failed, 0 skipped ======== h. NOTE An asterisk after the file name in the tab above the Code and Text Editor window indicates that the file has been changed since it was last saved. There is no need to manually save the file before building because the Build Solution command automatically saves the file. 2. On the Debug menu, click Start Without Debugging. A Command window opens and the program runs. The message Hello World appears, and then the program waits for the user to press any key, as shown in the following graphic: 3. Ensure that the Command window displaying the program has the focus, and then press Enter. The Command window closes and you return to the Visual Studio 2005 programming environment. NOTE If you run the program using Start Debugging on the Debug menu, the pplication runs but the Command window closes immediately without waiting for you to press a key. 4. In the Solution Explorer, click the TextHello project (not the solution), and then click Show All Files button. Entries named bin and obj appear above the C# source filenames. These entries correspond directly to folders named bin and obj in the project folder (My DocumentsVisual CSharp St ep by StepChapter 1TextHelloTextHello). These folders are created when you build your application, and they contain the executable version of the program and some other files. 10 SREEKANTH C# STEP BY STEP 5. 5. In the Solution Explorer, click the + to the left of the bin entry. Another folder named Debug appears. 6. 6. In the Solution Explorer, click the + to the left of the Debug entry. Three entries named TextHello. exe, TextHello. pdb, and TextHello. vshost. exe appear. The file TextHello. exe is the compiled program, and it is this file that runs when you click Start Without Debugging in the Debug menu. The other two files contain information that is used by Visual Studio 2005 if you run your program in Debug mode (when you click Start Debugging in the Debug menu). Command Line Compilation You can also compile your source files into an executable file manually by using the csc command-line C# compiler. You must first complete the following steps to set up your environment: 1. On the Windows Start menu, point to All Programs, point to Microsoft Visual Studio 2005, point to Visual Studio Tools, and click Visual Studio 2005 Command Prompt. A Command window opens, and the envionment variables PATH, LIB, and INCLUDE are configured to include the locations of the various . NET Framework libraries and utilities. TIP You can also run the vcvarsall. at script, located in the C:Program FilesMicrosoft Visual Studio 8VC folder, if you want to configure the environment variables while running in an ordinary Command Prompt window. 2. In the Visual Studio 2005 Command Prompt window, type the following command to go to the My DocumentsMicrosoft PressVisual CSharp Step by StepChapter 1TextHelloTextHello project folder: 3. cd Documents and SettingsYourNameMy Doc umentsMicrosoft PressVisual CSharp Step by StepChapter 1TextHelloTextHello 4. Type the following command: csc /out:TextHello. exe Program. cs 11 SREEKANTH C# STEP BY STEP This command creates the executable file TextHello. exe from the C# source file. If you dont use the /out command-line option, the executable file takes its name from the source file and is called Program. exe. 5. Run the program by typing the following command: TextHello The program should run exactly as before, except that you will not see the Press any key to continue prompt. Using Namespaces The example you have seen so far is a very small program. However, small programs can soon grow into bigger programs. As a program grows, it creates two problems. First, more code is harder to understand and maintain than less code. Second, more code usually means more names; more named data, more named methods, and more named classes. As the number of names increases so does the likelihood of the project build failing because two or more names clash (especially when the program uses third-party libraries). In the past, programmers tried to solve the name-clashing problem by prefixing names with some sort of qualifier (or set of qualifiers). This solution is not a good one because its not scalable; names become longer and you spend less time writing software and more time typing (there is a difference) and reading and re-reading incomprehensibly long names. Namespaces help solve this problem by creating a named container for other identifiers, such as classes. Two classes with the same name will not be confused with each other if they live in different namespaces. You can create a class named Greeting inside the namespace named TextHello, like this: namespace TextHello { class Greeting { } } You can then refer to the Greeting class as TextHello. Greeting in your own programs. If someone else also creates a Greeting class in a different namespace and installs it on your computer, your programs will still work as expected because they are using the TextHello. Greeting class. If you want to refer the new Greeting class, you must specify that you want the class from the new namespace. It is good practice to define all your classes in namespaces, and the Visual Studio 2005 environment follows this recommendation by using the name of your project as the toplevel namespace. The . NET Framework Software Developer Kit (SDK) also adheres to this recommendation; every class in the . NET Framework lives inside a namespace. For 12 SREEKANTH C# STEP BY STEP example, the Console class lives inside the System namespace. This means that its fully qualified name is actually System. Console. Of course, if you had to write the fully qualified name of a class every time, it would be no better that just naming the class SystemConsole. Fortunately, you can solve this problem with a using directive. If you return to the TextHello program in Visual Studio 2005 and look at the file Program. cs in the Code and Text Editor window, you will notice the following statements: using System; using System. Collections. Generic; using System. Text; The using statement brings a namespace into scope, and you no longer have to explictly qualify objects with the namespace they belong to in the code that follows. The three namespaces shown contain classes that are used so often that Visual Studio 2005 automatically adds these using statements every time you create a new project. You can add further using directives to the top of a source file. The following exercise demonstrates the concept of namespaces further. Try longhand names 1. In the Code And Text Editor window, comment out the using directive at the top of Program. cs: //using System; 2. On the Build menu, click Build Solution. The build fails, and the Output pane displays the following error message twice (once for each use of the Console class): The name Console does not exist in the current context. 3. In the Output pane, double-click the error message. The identifier that caused the error is selected in the Program. cs source file. TIP The first error can affect the reliability of subsequent diagnostic messages. If your build has more than one diagnostic message, correct only the first one, ignore all the others, and then rebuild. This strategy works best if you keep your source files small and work iteratively, building frequently. 4. In the Code and Text Editor window, edit the Main method to use the fully qualified name System. Console. Main should look like this: static void Main(string[] args) { System. Console. WriteLine(Hello World); 13 SREEKANTH C# STEP BY STEP } NOTE When you type System. , notice how the names of all the items in the System namespace are displayed by IntelliSense. 5. On the Build menu, click Build Solution. The build succeeds this time. If it doesnt, make sure Main is exactly as it appears in the preceding code, and then try building again. 6. Run the application to make sure it still works by clicking Start Without Debugging on the Debug menu. In the Solution Explorer, click the + to the left of the References entry. This displays the assemblies referenced by the Solution Explorer. An assembly is a library containing code written by other developers (such as the . NET Framework). In some cases, the classes in a namespace are stored in an assembly that has the same name (such as System), although this does not have to be the case—some assemblies hold more than one namespace. Whenever you use a namespace, you also need to make sure that you have referenced the assembly that contains the classes for that namespace; otherwise your program will not build (or run). Creating a Windows Forms Application So far you have used Visual Studio 2005 to create and run a basic Console application. The Visual Studio 2005 programming environment also contains everything youll need to create graphical Windows applications. You can design the form-based user interface of a Windows application interactively by using the Visual Designer. Visual Studio 2005 then generates the program statements to implement the user interface youve designed. From this explanation, it follows that Visual Studio 2005 allows you to maintain two views of the application: the Design View and the Code View. The Code and Text Editor window (showing the program statements) doubles as the Design View window (allowing you to lay out your user interface), and you can switch between the two views whenever you want. In the following set of exercises, youll learn how to create a Windows program in Visual Studio 2005. This program will display a simple form containing a text box where you can enter your name and a button that, when clicked, displays a personalized greeting in a message box. You will use the Visual Designer to create your user interface by placing controls on a form; inspect the code generated by Visual Studio 2005; use the Visual Designer to change the control properties; use the Visual Designer to resize the form; write the code to respond to a button click; and run your first Windows program. Create a Windows project in Visual Studio 2005 1. On the File menu, point to New, and then click Project. The New Project dialog box opens. 2. In the Project Types pane, click Visual C#. 14 SREEKANTH C# STEP BY STEP 3. In the Templates pane, click the Windows Application icon. . Ensure that the Location field refers to your My DocumentsVisual CSharp Step by StepChapter 1 folder. 5. In the Name field, type WinFormHello. 6. In the Solutions field, ensure that Create new Solution is selected. This action creates a new solution for holding the Windows application. The alternative, Add to Solution, will add the project to the TextHello solution. 7. Click OK. Visual St udio 2005 closes your current application (prompting you to save it first of necessary) and creates and displays an empty Windows form in the Design View window. In the following exercise, youll use the Visual Designer to add three controls to the Windows form and examine some of the C# code automatically generated by Visual Studio 2005 to implement these controls. Create the user interface 1. Click the Toolbox tab that appears to the left of the form in the Design View. The Toolbox appears, partially obscuring the form and displaying the various components and controls that you can place on a Windows form. 2. In the Toolbox, click the + sign by Common Controls to display a list of controls that are used by most Windows Forms applications. 15 SREEKANTH C# STEP BY STEP 3. Click Label, and then click the visible part of the form. A Label control is added to the form, and the Toolbox disappears from view. TIP If you want the Toolbox to remain visible but not hide any part of the form, click the Auto Hide button to the right in Toolbox title bar (it looks like a pin). The Toolbox appears permanently on the left side of the Visual Studio 2005 window, and the Design View shrinks to accommodate it. (You might lose a lot of space if you have a low-resolution screen. ) Clicking the Auto Hide button once more causes the Toolbox to disappear again. 4. The Label control on the form is probably not exactly where you want it. You can click and drag the controls you have added to a form to reposition them. Using this technique, move the Label control so that it is positioned towards the upper-left corner of the form. (The exact placement is not critical for this application. ) 5. On the View menu, click Properties Window. The Properties window appears on the right side of the screen. The Properties window allows you to set the properties for items in a project. It is context sensitive, in that it displays the properties for the currently selected item. If you click anywhere on the form displayed in the Design View, you will see that the Properties windows displays the properties for the form itself. If you click the Label control, the window displays the properties for the label instead. 6. Click the Label control on the form. In the Properties window, locate the Text property, change it from label1 to Enter your name, and then press Enter. On the form, the labels text changes to Enter Your Name. TIP By default, the properties are displayed in categories. If you prefer to display the properties in alphabetical order, click the Alphabetical button that appears above the properties list. . Display the Toolbox again. Click TextBox, and then click the form. A TextBox control is added to the form. Move the TextBox control so that it is directly underneath the Label control. TIP When you drag a control on a form, alignment handles appear automatically when the control becomes aligned vertically or horizontally with other controls. This g ive you a quick visual cue for making sure that controls are lined up neatly. 8. While the TextBox control is selected, locate the Text property in the Properties window, type here, and then press Enter. On the form, the word here appears in the text box. 9. In the Properties window, find the (Name) property. Visual Studio 2005 gives controls and forms default names, which, although they are a good starting point, are not always very meaningful. Change the name of the TextBox control to userName. 16 SREEKANTH C# STEP BY STEP NOTE We will talk more about naming conventions for controls and variables in Chapter 2, â€Å"Working with Variables, Operators, and Expressions. † 10. Display the Toolbox again, click Button, and then click the form. Drag the Button control to the right of the TextBox control on the form so that it is aligned horizontally with the text box. 11. Using the Properties window, change the Text property of the Button control to OK. Change its (Name) property to ok. The caption on the button changes. 12. Click the Form1 form in the Design View window. Notice that resize handles (small squares) appear on the lower edge, the right-hand edge, and the righthand bottom corner of the form. 13. Move the mouse pointer over the resize handle. The pointer changes to a diagonal double-headed arrow. 14. Hold down the left mouse button, and drag the pointer to resize the form. Stop dragging and release the mouse button when the spacing around the controls is roughly equal. TIP You can resize many controls on a form by selecting the control and dragging one of the resize handles that appears in the corners of the control. Note that a form has only one resize handle, whereas most controls have four (one on each corner). On a form, any resize handles other than the one in the lower-right corner would be superfluous. Also note that some controls, such as Label controls, are automatically sized based on their contents and cannot be resized by dragging them. The form should now look similar to the one in the following graphic. 1. In the Solution Explorer, right-click the file Form1. s, and then click View Code. The Form1. cs source file appears in the Code and Text Editor window. There are now two tabs named Form1. cs above the Code and Text Editor/Design View window. You can click the one suffixed with [Design] to return to Design View window at any time. Form1. cs contains some of the code automatically generated by Visual Studio 2005. You should note the following elements: 17 SREEKANTH C# STEP BY STEP o using directives Visual Studio 2005 has written a number of using directives at the top of the source file (more than for the previous example). For example: using System. Windows. Forms; The additional namespaces contain the classes and controls used when building graphical applications—for example, the TextBox, Label, and Button classes. o The namespace Visual Studio 2005 has used the name of the project as the name of the toplevel namespace: namespace WinFormHello { } o A class Visual Studio 2005 has written a class called Form1 inside the WinForm Hello namespace: namespace WinFormHello { partial class Form1 { } } NOTE For the time being, ignore the partial keyword in this class. I will describe its purpose shortly. This class implements the form you created in the Design View. Classes are discussed in Chapter 7. ) There does not appear to be much else in this class—there is a little bit of code known as a constructor that calls a method called InitializeComponent, but nothing else. (A constructor is a special method with the same name as the class. It is executed when the form is created and can contain code to initialize the form. Constructors ar e also discussed in Chapter 7. ) However, Visual Studio 2005 is performing a sleight of hand and is hiding a few things from you, as I will now demonstrate. In a Windows Forms application, Visual Studio 2005 actually generates a potentially large amount of code. This code performs operations such as 18 SREEKANTH C# STEP BY STEP creating and displaying the form when the application starts, and creating and positioning the various controls on the form. However, this code can change as you add controls to a form and change their properties. You are not expected to change this code (indeed, any changes