C# could theoretically be compiled to machine code, but in real life, it's always used in combination with the .NET framework. Therefore, applications written in C#, requires the .NET framework to be installed on the computer running the application. While the .NET framework makes it possible to use a wide range of languages, C# is sometimes referred to as THE .NET language, perhaps because it was designed together with the framework.
C# is an Object Oriented language and does not offer global variables or functions. Everything is wrapped in classes, even simple types like int and string, which inherits from the System.Object class.
In the following chapters, you will be guided through the most important topics about C#.
C# is a modern, general-purpose object oriented programming language developed by Microsoft and approved by Ecma and ISO.
C# was developed by Anders Hejlsberg and his team during the development of .Net Framework.
C# is designed for Common Language Infrastructure (CLI), which consists of the executable code and runtime environment that allows use of various high-level languages to be used on different computer platforms and architectures.
The following reasons make C# a widely used professional language:
- Modern, general purpose programming language
- Object oriented.
- Component oriented.
- Easy to learn.
- Structured language.
- It produces efficient programs.
- It can be compiled on a variety of computer platforms.
- Part of .Net Framework.
Strong Programming Features of C#
Although C# constructs closely follows traditional high level languages C and C++ and being an object oriented programming language, it has strong resemblance with Java, it has numerous strong programming features that make it endearing to multitude of programmers worldwide.
Following is the list of few important features:
- Boolean Conditions
- Automatic Garbage Collection
- Standard Library
- Assembly Versioning
- Properties and Events
- Delegates and Events Management
- Easy to use Generics
- Indexers
- Conditional Compilation
- Simple Multithreading
- LINQ and Lambda Expressions
- Integration with WindowsIn this chapter, we will discuss the tools required for creating C# programming. We have already mentioned that C# is part of .Net framework and is used for writing .Net applications. Therefor before discussing the available tools for running a C# program, let us understand how C# relates to the .Net framework.
The .Net Framework
The .Net framework is a revolutionary platform that helps you to write the following types of applications:- Windows applications
- Web applications
- Web services
The .Net framework applications are multi-platform applications. The framework has been designed in such a way that it can be used from any of the following languages: C#, C++, Visual Basic, Jscript, COBOL etc. All these languages can access the framework as well as communicate with each other.The .Net framework consists of an enormous library of codes used by the client languages like C#. Following are some of the components of the .Net framework:- Common Language Runtime (CLR)
- The .Net Framework Class Library
- Common Language Specification
- Common Type System
- Metadata and Assemblies
- Windows Forms
- ASP.Net and ASP.Net AJAX
- ADO.Net
- Windows Workflow Foundation (WF)
- Windows Presentation Foundation
- Windows Communication Foundation (WCF)
- LINQ
For the jobs each of these components perform, please see ASP.Net - Introduction and for details of each component, please consult Microsoft's documentation.Integrated Development Environment (IDE) For C#
Microsoft provides the following development tools for C# programming:- Visual Studio 2010 (VS)
- Visual C# 2010 Express (VCE)
- Visual Web Developer
The last two are freely available from Microsoft official website. Using these tools you can write all kinds of C# programs from simple command-line applications to more complex applications. You can also write C# source code files using a basic text editor, like Notepad, and compile the code into assemblies using the command-line compiler, which is again a part of the .NET Framework.Visual C# Express and Visual Web Developer Express edition are trimmed down versions of Visual Studio and has the same look and feel. They retain most features of Visual Studio. In this tutorial, we have used Visual C # 2010 Express.You can download it from Microsoft Visual Studio. It gets automatically installed in your machine. Please note that you need an active internet connection for installing the express edition.Writing C# Programs on Linux or Mac OS
Although the.NET Framework runs on the Windows operating system, there are some alternative versions that work on other operating systems. Mono is an open-source version of the .NET Framework, which includes a C# compiler and runs on several operating systems, including various flavors of Linux and Mac OS. Kindly check Go Mono.The stated purpose of Mono is not only to be able to run Microsoft .NET applications cross-platform, but also to bring better development tools to Linux developers. Mono can be run on many operating systems including Android, BSD, iOS, Linux, OS X, Windows, Solaris and UNIX.Before we study basic building blocks of the C# programming language, let us look at a bare minimum C# program structure so that we can take it as a reference in upcoming chapters.C# Hello World Example
A C# program basically consists of the following parts:- Namespace declaration
- A class
- Class methods
- Class attributes
- A Main method
- Statements & Expressions
- Comments
Let us look at a simple code that would print the words "Hello World":using System; namespace HelloWorldApplication { class HelloWorld { static void Main(string[] args) { /* my first program in C# */ Console.WriteLine("Hello World"); Console.ReadKey(); } } }
When the above code is compiled and executed, it produces following result:Hello World
Let us look at various parts of the above program:- The first line of the program using System; - the using keyword is used to include the Systemnamespace in the program. A program generally has multiple using statements.
- The next line has the namespace declaration. A namespace is a collection of classes. TheHelloWorldApplication namespace contains the class HelloWorld.
- The next line has a class declaration, the class HelloWorld, contains the data and method definitions that your program uses. Classes generally would contain more than one method. Methods define the behavior of the class. However, the HelloWorld class has only one methodMain.
- The next line defines the Main method, which is the entry point for all C# programs. The Mainmethod states what the class will do when executed
- The next line /*...*/ will be ignored by the compiler and it has been put to add additionalcomments in the program.
- The Main method specifies its behavior with the statement Console.WriteLine("Hello World");WriteLine is a method of the Console class defined in the System namespace. This statement causes the message "Hello, World!" to be displayed on the screen.
- The last line Console.ReadKey(); is for the VS.NET Users. This makes the program wait for a key press and it prevents the screen from running and closing quickly when the program is launched from Visual Studio .NET.
Its worth to note the following points:- C# is case sensitive.
- All statements and expression must end with a semicolon (;).
- The program execution starts at the Main method.
- Unlike Java, file name could be different from the class name.
Compile & Execute a C# Program:
If you are using Visual Studio.Net for compiling and executing C# programs, take the following steps:- Start Visual Studio.
- On the menu bar, choose File, New, Project.
- Choose Visual C# from templates, and then choose Windows.
- Choose Console Application.
- Specify a name for your project, and then choose the OK button.
- The new project appears in Solution Explorer.
- Write code in the Code Editor.
- Click the Run button or the F5 key to run the project. A Command Prompt window appears that contains the line Hello World.
You can compile a C# program by using the command line instead of the Visual Studio IDE:- Open a text editor and add the above mentioned code.
- Save the file as helloworld.cs
- Open the command prompt tool and go to the directory where you saved the file.
- Type csc helloworld.cs and press enter to compile your code.
- If there are no errors in your code the command prompt will take you to the next line and would generate helloworld.exe executable file.
- Next, type helloworld to execute your program.
- You will be able to see "Hello World" printed on the screen.C# is an object oriented programming language. In Object Oriented Programming methodology a program consists of various objects that interact with each other by means of actions. The actions that an object may take are called methods. Objects of the same kind are said to have the same type or, more often, are said to be in the same class.For example, let us consider a Rectangle object. It has attributes like length and width. Depending upon the design, it may need ways for accepting the values of these attributes, calculating area and display details.Let us look at an implementation of a Rectangle class and discuss C# basic syntax, on the basis of our observations in it:
using System; namespace RectangleApplication { class Rectangle { // member variables double length; double width; public void Acceptdetails() { length = 4.5; width = 3.5; } public double GetArea() { return length * width; } public void Display() { Console.WriteLine("Length: {0}", length); Console.WriteLine("Width: {0}", width); Console.WriteLine("Area: {0}", GetArea()); } } class ExecuteRectangle { static void Main(string[] args) { Rectangle r = new Rectangle(); r.Acceptdetails(); r.Display(); Console.ReadLine(); } } }
When the above code is compiled and executed, it produces following result:Length: 4.5 Width: 3.5 Area: 15.75
The using Keyword
The first statement in any C# program isusing System;
The using keyword is used for including the namespaces in the program. A program can include multiple using statements.The class Keyword
The class keyword is used for declaring a class.Comments in C#
Comments are used for explaining code. Compilers ignore the comment entries. The multiline comments in C# programs start with /* and terminates with the characters */ as shown below:/* This program demonstrates The basic syntax of C# programming Language */Single line comments are indicated by the '//' symbol. For example,}//end class Rectangle
Member Variables
Variables are attributes or data members of a class, used for storing data. In the preceding program, the Rectangle class has two member variables named length and width.Member Functions
Functions are set of statements that perform a specific task. The member functions of a class are declared within the class. Our sample class Rectangle contains three member functions:AcceptDetails, GetArea and Display.Instantiating a Class
In the preceding program, the class ExecuteRectangle is used as a class which contains the Main()method and instantiates the Rectangle class.Identifiers
An identifier is a name used to identify a class, variable, function, or any other user-defined item. The basic rules for naming classes in C# are as follows:- A name must begin with a letter that could be followed by a sequence of letters, digits (0 - 9) or underscore. The first character in an identifier cannot be a digit.
- It must not contain any embedded space or symbol like ? - +! @ # % ^ & * ( ) [ ] { } . ; : " ' / and \. However an underscore ( _ ) can be used.
- It should not be a C# keyword.
C# Keywords
Keywords are reserved words predefined to the C# compiler. These keywords cannot be used as identifiers, however, if you want to use these keywords as identifiers, you may prefix the keyword with the @ character.In C# some identifiers have special meaning in context of code, such as get and set, these are called contextual keywords.The following table lists the reserved keywords and contextual keywords in C#:Reserved Keywords 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 in (generic
modifier)int interface internal is lock long namespace new null object operator out out
(generic
modifier)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 Contextual Keywords add alias ascending descending dynamic from get global group into join let orderby partial
(type)partial
(method)remove select set
In C#, variables are categorized into the following types:- Value types
- Reference types
- Pointer types
Value Types
Value type variables can be assigned a value directly. They are derived from the classSystem.ValueType.The value types directly contain data. Some examples are int, char, float, which stores numbers, alphabets and floating point numbers respectively. When you declare an int type, the system allocates memory to store the value.The following table lists the available value types in C# 2010:Type Represents Range Default
Valuebool Boolean value True or False False byte 8-bit unsigned integer 0 to 255 0 char 16-bit Unicode character U +0000 to U +ffff '\0' decimal 128-bit precise decimal values with 28-29 significant digits (-7.9 x 1028 to 7.9 x 1028) / 100 to 28 0.0M double 64-bit double-precision floating point type (+/-)5.0 x 10-324 to (+/-)1.7 x 10308 0.0D float 32-bit single-precision floating point type -3.4 x 1038 to + 3.4 x 1038 0.0F int 32-bit signed integer type -2,147,483,648 to 2,147,483,647 0 long 64-bit signed integer type -923,372,036,854,775,808 to 9,223,372,036,854,775,807 0L sbyte 8-bit signed integer type -128 to 127 0 short 16-bit signed integer type -32,768 to 32,767 0 uint 32-bit unsigned integer type 0 to 4,294,967,295 0 ulong 64-bit unsigned integer type 0 to 18,446,744,073,709,551,615 0 ushort 16-bit unsigned integer type 0 to 65,535 0 To get the exact size of a type or a variable on a particular platform, you can use the sizeof method. The expression sizeof(type) yields the storage size of the object or type in bytes. Following is an example to get the size of int type on any machine:namespace DataTypeApplication { class Program { static void Main(string[] args) { Console.WriteLine("Size of int: {0}", sizeof(int)); Console.ReadLine(); } } }
When the above code is compiled and executed, it produces following result:Size of int: 4
Reference Types
The reference types do not contain the actual data stored in a variable, but they contain a reference to the variables.In other words, they refer to a memory location. Using more than one variable, the reference types can refer to a memory location. If the data in the memory location is changed by one of the variables, the other variable automatically reflects this change in value. Example of built in reference types are:object, dynamic and string.OBJECT TYPE
The Object Type is the ultimate base class for all data types in C# Common Type System(CTS). Object is an alias for System.Object class. So object types can be assigned values of any other types, value types, reference types, predefined or user-defined types. However, before assigning values, it needs type conversion.When a value type is converted to object type, it is called boxing and on the other hand, when an object type is converted to a value type it is called unboxing.object obj; obj = 100; // this is boxing
DYNAMIC TYPE
You can store any type of value in the dynamic data type variable. Type checking for these types of variables takes place at runtime.Syntax for declaring a dynamic type is:dynamic <variable_name> = value;
For example,dynamic d = 20;
Dynamic types are similar to object types except that, type checking for object type variables takes place at compile time, whereas that for the dynamic type variables take place at run time.STRING TYPE
The String Type allows you to assign any string values to a variable. The string type is an alias for the System.String class. It is derived from object type. The value for a string type can be assigned using string literals in two forms: quoted and @quoted.For example,String str = "Tutorials Point";
A @quoted string literal looks like:@"Tutorials Point";
The user defined reference types are: class, interface, or delegate. We will discuss these types in later chapter.Pointer Types
Pointer type variables store the memory address of another type. Pointers in C# have the same capabilities as in C or C++.Syntax for declaring a pointer type is:type* identifier;
For example,char* cptr; int* iptr;
We will discuss pointer types in the chapter 'Unsafe Codes'.Type conversion is basically type casting, or converting one type of data to another type. In C#, type casting has two forms:- Implicit type conversion - these conversions are performed by C# in a type-safe manner. Examples are conversions from smaller to larger integral types, and conversions from derived classes to base classes.
- Explicit type conversion - these conversions are done explicitly by users using the pre-defined functions. Explicit conversions require a cast operator.
The following example shows an explicit type conversion:namespace TypeConversionApplication { class ExplicitConversion { static void Main(string[] args) { double d = 5673.74; int i; // cast double to int. i = (int)d; Console.WriteLine(i); Console.ReadKey(); } } }
When the above code is compiled and executed, it produces following result:5673
C# Type Conversion Methods
C# provides the following built-in type conversion methods:S.N Methods & Description 1 ToBoolean
Converts a type to a Boolean value, where possible.2 ToByte
Converts a type to a byte.3 ToChar
Converts a type to a single Unicode character, where possible.4 ToDateTime
Converts a type (integer or string type) to date-time structures.5 ToDecimal
Converts a floating point or integer type to a decimal type.6 ToDouble
Converts a type to a double type.7 ToInt16
Converts a type to a 16-bit integer.8 ToInt32
Converts a type to a 32-bit integer.9 ToInt64
Converts a type to a 64-bit integer.10 ToSbyte
Converts a type to a signed byte type.11 ToSingle
Converts a type to a small floating point number.12 ToString
Converts a type to a string.13 ToType
Converts a type to a specified type.14 ToUInt16
Converts a type to an unsigned int type.15 ToUInt32
Converts a type to an unsigned long type.16 ToUInt64
Converts a type to an unsigned big integer.The following example converts various value types to string type:namespace TypeConversionApplication { class StringConversion { static void Main(string[] args) { int i = 75; float f = 53.005f; double d = 2345.7652; bool b = true; Console.WriteLine(i.ToString()); Console.WriteLine(f.ToString()); Console.WriteLine(d.ToString()); Console.WriteLine(b.ToString()); Console.ReadKey(); } } }
When the above code is compiled and executed, it produces following result:75 53.005 2345.7652 True
A variable is nothing but a name given to a storage area that our programs can manipulate. Each variable in C# has a specific type, which determines the size and layout of the variable's memory; the range of values that can be stored within that memory; and the set of operations that can be applied to the variable.We have already discussed various data types. The basic value types provided in C# can be categorized as:Type Example Integral types sbyte, byte, short, ushort, int, uint, long, ulong and char Floating point types float and double Decimal types decimal Boolean types true or false values, as assigned Nullable types Nullable data types C# also allows defining other value types of variable like enum and reference types of variables likeclass, which we will cover in subsequent chapters. For this chapter, let us study only basic variable types.Variable Declaration in C#
Syntax for variable declaration in C# is:<data_type> <variable_list>;
Here, data_type must be a valid C# data type including char, int, float, double, or any user defined data type etc., and variable_list may consist of one or more identifier names separated by commas.Some valid variable declarations along with their definition are shown here:int i, j, k; char c, ch; float f, salary; double d;
You can initialize a variable at the time of declaration as:int i = 100;
Variable Initialization in C#
Variables are initialized (assigned a value) with an equal sign followed by a constant expression. The general form of initialization is:variable_name = value;
Variables can be initialized (assigned an initial value) in their declaration. The initializer consists of an equal sign followed by a constant expression as:<data_type> <variable_name> = value;
Some examples are:int d = 3, f = 5; /* initializing d and f. */ byte z = 22; /* initializes z. */ double pi = 3.14159; /* declares an approximation of pi. */ char x = 'x'; /* the variable x has the value 'x'. */
It is a good programming practice to initialize variables properly otherwise, sometime program would produce unexpected result.Try following example which makes use of various types of variables:namespace VariableDeclaration { class Program { static void Main(string[] args) { short a; int b ; double c; /* actual initialization */ a = 10; b = 20; c = a + b; Console.WriteLine("a = {0}, b = {1}, c = {2}", a, b, c); Console.ReadLine(); } } }
When the above code is compiled and executed, it produces following result:a = 10, b = 20, c = 30
Accepting Values from User
The Console class in the System namespace provides a function ReadLine() for accepting input from the user and store it into a variable.For example,int num; num = Convert.ToInt32(Console.ReadLIne());
The function Convert.ToInt32() converts the data entered by the user to int data type, becauseConsole.ReadLine() accepts the data in string format.Lvalues and Rvalues in C#:
There are two kinds of expressions in C#:- lvalue : An expression that is an lvalue may appear as either the left-hand or right-hand side of an assignment.
- rvalue : An expression that is an rvalue may appear on the right- but not left-hand side of an assignment.
Variables are lvalues and so may appear on the left-hand side of an assignment. Numeric literals are rvalues and so may not be assigned and can not appear on the left-hand side. Following is a valid statement:int g = 20;
But following is not a valid statement and would generate compile-time error:10 = 20;
- For details please visit: http://www.tutorialspoint.com/csharp/csharp_variables.htm
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