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C# : C Sharp
1) Introduction to .NET2) An Introduction To The .NET Framework3) C# System Requirements4) Application Types in C#5) To Begin With C# Programming6) C# Types7) Predefined Reference Types8) Data types in C#9) Classes and Object Model in .NET10) Property in C# class11) Method Overloading in C#12) C# Tutorial Namespaces13) Interfaces in C#14) Delegates in C#15) Events in C#16) Reflection in C#
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Introduction to .NET
Introduction:
Before we start explaining what .Net is? Lets discuss about Internet on business organization.
There are three phases of Internet.
y First phase starts early in 1990s, which brought big revolution. Organizations created and
launched their websites. The core idea behind this is to know hit rate means how many peoples
are interested in their product and services. So that they can update their products accordingly.
y The 2nd is in which we are right now. Organization is generating revenues from on-line trading.
y We are moving into 3rd phase and here idea is to communicate peoples, partner and share
resources which are geographically far to run business successfully.
Here .net comes into picture, which is designed by Microsoft people, which provide to build
net based application which connect peoples and data at remote locations through any devices
(i.e. laptop, mobiles, and pda)
What is .net basically?
NET is the Microsoft Web services strategy to connect information, people, systems, anddevices through software. Integrated across the Microsoft platform, .NET technology
provides the ability to quickly build, deploy, manage, and use connected, security-enhancedsolutions with Web services. .NET-connected solutions enable businesses to integrate their
systems more rapidly and in a more agile manner and help them realize the promise ofinformation anytime, anywhere, on any device.
The Microsoft platform includes everything a business needs to develop and deploy a Webservice-connected IT architecture: servers to host Web services, development tools to create
them, applications to use them, and a worldwide network of more than 35k Microsoft
Certified Partner organizations to provide any help we need.
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An Introduction To The .NET Framework
.NET Framework
.NET is Microsofts new strategy for the development and deployment of software.
Depending on your interests and development background, we may already have a number of
preconceived notions regarding
y NET fundamentally changes the way applications execute under the Windows OperatingSystem.
y with .NET Microsoft is, in effect, abandoning its traditional Way of applicationdevelopment, one which favors compiled components, and is embracing Interpreted
technology (similar, in many ways, to the Java Paradigm).y NET brings about significant changes to both C++ and Visual Basic, and introduces a new
language called C# .
y NET is built from the ground up with the Internet in mind, embracing open Internetstandards such as XML and HTTP.
The .NET Framework can be distilled into the following three entities:
The Time-wasters will surround you all the sides and will tear away at your minutes and
hours, holding the back from producing a critical results which are vital to the success in thecareer.
y The Common Language Runtime (CLR)CLR is execution environment for all programs in the .NET Framework. The CLR is
similar to a Java Virtual Machine (VM) in that it interprets byte code and executes it on the
fly, while simultaneously providing services such as garbage collection and exception
handling. Unlike a Java VM, which is limited to the Java language, the CLR is accessible
from any compiler that produces Microsoft Intermediate Language (IL) code, which is
similar to Java byte code. Code that executes inside the CLR is referred to as managed
code. Code that executes outside its boundaries is called unmanaged code.
USER INTERFACE ANDWINDOWS FORM
BASE CLASS LIBRARIES
COMMON LANGUAGE RUNTIME
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. Net framework
y The Base class librariesIt provides hundreds of prewritten services that user uses. These classes are the building blocks for
.NET applications. Every language had its own unique supporting libraries, accessible only from
that particular language. This library includes UI,Data, Web, Diagonostic, and Ado.
y User interface and Win formsThis includes ASP.net pages or windows forms to interact with the application.
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System Requirements
System Requirements
In order to install the .NET Framework on your machine, Microsoft recommends the
following system configuration:
y Processor: Minimum Pentium II-450Mhz (Pentium III-650Mhz recommended).y Operating System: Windows 2000 (Server or Professional), Windows XP, or Windows NT
4.0 Server.
y Memory: 96 MB (128 MB recommended) for Windows 2000 Professional, 192MB (256MB recommended) for Windows 2000 server.
y Hard drive: 500MB free on the drive where the OS is installed (usually C:\) and 2.5 Gigsfree on the installation drive (where VS.NET will be installed)..
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An introduction to C# (pronounced "C sharp")C# (pronounced "C sharp") is a simple, modern, object-oriented, and type-safe
programming language. It will immediately be familiar to C and C++ programmers. C#
combines the high productivity of Rapid Application Development (RAD) languages.
Visual C# .NET is Microsoft's C# development tool. It includes an interactive
development environment, visual designers for building Windows and Web applications, a
compiler, and a debugger. Visual C# .NET is part of a suite of products, called Visual
Studio .NET, that also includes Visual Basic .NET, Visual C++ .NET, and the JScript
scripting language. All of these languages provide access to the Microsoft .NET
Framework, which includes a common execution engine and a rich class library. The
.NET Framework defines a "Common Language Specification" (CLS), a sort of lingua
franca that ensures seamless interoperability between CLS-compliant languages and classlibraries. For C# developers, this means that even though C# is a new language, it hascomplete access to the same rich class libraries that are used by seasoned tools such as
Visual Basic .NET and Visual C++ .NET. C# itself does not include a class library
Features of c#:
As a new programming language following features made this different from other
languages: -
y Simpley Type safey Versioning: making new version of an application from existing one to work.y Follows all OOPs paradigmy Automatic garbage collectiony Flexible
What c# has added?
As compared to c++, following concepts are added into c: -
y Assembliesy Versioningy Indexersy Boxing
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y Delegates
Application Types in C#
Application Types in C#
Class Library Creates a project for creating classes that can be
used in other applications.
Console Application Creates a Visual C# application with a command-line
interface.
ASP.NET Web
Application
Creates a Visual C# application with a Web user
interface.
ASP.NET Web Service Creates an XML Web service with Visual C# that other
applications can access.
ASP.NET Mobile Web
Application
Creates an application viewable on PDAs, cell phones,
and other mobile devices.
Empty Project Creates an empty project for creating a local
application.
Empty Web Project Creates an empty project for creating a Web
application.
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To Begin With C# Programming
To Begin With C# Programming
C# is a language that provides
y Simplicity of Visual Basic
y Power of C++
y Concentrate on the high-value tasks;
y Portability of Java
First C# program to display hello, world on the console
using System;
class Hello
{
static void Main ()
{
Console.WriteLine("hello, world");
}
}
The source code for a C# program is typically stored in one or more text files with a file
extension of .cs, as in hello.cs. Using the command-line compiler provided with Visual
Studio .NET, such a program can be compiled with the command-line directive
csc hello.cs , which produces an application, named hello.exe. The output produced by
this application when it is run is:
hello, world
The using System; directive references a namespace called System that is provided by the
Microsoft .NET Framework class library. This namespace contains the Console class
referred to in the Main method. Namespaces provide a hierarchical means of organizing
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the elements of one or more programs. A "using" directive enables unqualified use of the
types that are members of the namespace. The "hello, world" program uses Console.
WriteLine as shorthand forSystem.Console.WriteLine.
The Main method is a member of the class Hello. It has the static modifier, and so it is amethod on the class Hello rather than on instances of this class. The entry point for an
application the method that is called to begin execution is always a static methodnamed Main. The "hello, world" output is produced using a class library. The language
does not itself provide a class library. Instead, it uses a class library that is also used by
Visual Basic .NET and Visual C++.NET.
The program does not use a global method for Main. Methods and variables are not
supported at the global level; such elements are always contained within type declarations
(e.g., class and struct declarations).
C# language does not use either "::" or "->" operators. The "::" is not an operator at all,
and the "->" operator is used in only a small fraction of programs those that employ
unsafe code. The separator "." is used in compound names such as Console. WriteLine.
The program does not contain forward declarations. Forward declarations are neverneeded, as declaration order is not significant. C# does not use #include to import program
text. Dependencies among programs are handled symbolically rather than textually. This
approach eliminates barriers between applications written using multiple languages.
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.NET Type
TYPE:
C# supports two kinds of types: value types and reference types. Value types include simpletypes (e.g., char, int, and float), enum types, and struct types.
Reference types include class types, interface types, delegate types, and array types.
Value types differ from reference types in that variables of the value types directly contain
their data, whereas variables of the reference types store references to objects. With reference
types, it is possible for two variables to reference the same object, and thus possible for
operations on one variable to affect the object referenced by the other variable. With valuetypes, the variables each have their own copy of the data, and it is not possible for operations
on one to affect the other. The example
The example using System;
class Class1
{
public int Value = 0;
}class Test
{
static void Main ()
{
int val1 = 0;
int val2 = val1;
val2 = 123;
Class1 ref1 = new Class1();
Class1 ref2 = ref1;
ref2.Value = 123;
Console.WriteLine("Values: {0}, {1}", val1, val2);
Console.WriteLine("Refs: {0}, {1}", ref1.Value, ref2.Value);
}
}
The output produced is
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Values: 0, 123 Refs: 123, 123
The lines
Console.WriteLine ("Values: {0}, {1}", val1, val2);
Console.WriteLine ("Refs: {0}, {1}", ref1. Value, ref2. Value);
The first argument is a string, which may contain numbered placeholders like {0} and {1}.
Each placeholder refers to a trailing argument with {0} referring to the second argument, {1}
referring to the third argument, and so on. Before the output is sent to the console, eachplaceholder is replaced with the formatted value of its corresponding argument
Developers can define new value types through enum and struct declarations, and can definenew reference types via class, interface, and delegate declarations.
Eliminating the Time Wasters
The Time-wasters will surround you all the sides and will tear away at your minutes andhours, holding the back from producing a critical results which are vital to the success in the
career.
y Eliminate a time wasters in life;
y The Law of an Excluded Alternative;
y Identify a major time-wasters;
y Practical ways to overcome and avoid them if possible.
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Predefined Reference Types
Predefined Reference Types
The predefined reference types are object and string. The type object is the ultimate base typeof all other types. The type string is used to represent Unicode string values. Values of type
string are immutable.
Object
The ultimate base type of all other types object o = null;
string
String type; a string is a sequence ofUnicode characters string s = "hello";
Predefined value types
The predefined value types include signed and unsigned integral types, floating-point types,
and the types bool, char, and decimal. The signed integral types are sbyte, short, int, and long;the unsigned integral types are byte, ushort, uint, and ulong; and the floating-point types are
float and double.
y Eliminate a time wasters in life;
y The Law of an Excluded Alternative;
y Identify a major time-wasters;
y Practical ways to overcome and avoid them if possible.
sbyte 8-bit signed integral type sbyte val = 12;
short 16-bit signed integral type short val = 12;
int 32-bit signed integral type int val = 12;
long 64-bit signed integral type long val1 = 12;
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long val2 = 34L;
byte 8-bit unsigned integral type byte val1 = 12;
ushort 16-bit unsigned integral type ushort val1 = 12;
uint 32-bit unsigned integral type uint val1 = 12;
float Single-precision floating point type float val = 1.23F;
doubleDouble-precision floating point type double val1 = 1.23;
double val2 = 4.56D;
Bool
The bool type is used to represent Boolean values: values that are either true or false. The
inclusion of bool makes it easier to write self-documenting code, and also helps eliminate theall-too-common C++ coding error in which a developer mistakenly uses "=" when "=="
should have been used. In C#, the example
int i =;
F (i);
if (i = 0) // the test should be (i == 0)
G();
results in a compile-time error because the expression i = 0 is of type int,
and if statements require an expression of type bool.
Boolean type;
a bool value is either true or false
bool val1 = true;
bool val2 = false;
char
The char type is used to represent Unicode characters. A variable of type char represents a
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single 16-bit Unicode character. Character type; a char value is a Unicode character char val= 'h';
Decimal
The decimal type is appropriate for calculations in which rounding errors caused by floating
point representations are unacceptable. Common examples include financial calculations such
as tax computations and currency conversions. The decimal type provides 28 significant
digits.
Precise decimal type with 28 significant digits
decimal val = 1.23M;
Each of the predefined types is shorthand for a system-provided type. For example, the
keyword int refers to the struct System.Int32. As a matter of style, use of the keyword is
favored over use of the complete system type name.
Two expressions of type int are considered equal if they represent the same integer value.
Two expressions of type object are considered equal if both refer to the same object, or if
both are null. Two expressions of type string are considered equal if the string instances have
identical lengths and identical characters in each character position, or if both are null.
Differences between Values Types and Reference Types.
The following table shows some of the differences between values types and reference types.
Value types Reference types
Allocated on stack Allocated on heap
A value type variable contains the
data itself
Reference type variable contains the address of memory
location where data is actually stored
When we copy a value type variable
to another one, the actual data is
copied and each variable can be
independently manipulated.
When copying a reference type variable to another
variable, only the memory address is copied. Both
variables will still point to the same memory location,
which means, if we change one variable, the value will bechanged for the other variable too.
integer, float, boolean, double etc are
value types.string and object are reference types.
struct is value type. Classes and interfaces are reference types.
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Data types in C# and .NET
Data types in C# and .NET
Data Types are the basic building block of any language.
Microsoft has tried to standardize the data types in .NET framework by introducing a limited, fixed
set of types that can be used to represent almost anything in programming world.
C++ was very rich in data types, but that leads to confusion too. Especially, when we write
components that may be consumed by applications written in other platforms, we have tomake sure the types used are compatible with other platforms too!
NET types start from a clean slate. All .NET languages share the same types. So, they areall compatible and no worries. This means, we can call C# code from VB.NET and vice
versa, without worrying about type conversions.
NET data types are either structures or classes, part of the System namespace. For example,the following data types are implemented as struct in .NET:
y Int16
y Int32
y Double
(String is implemented as a class in .NET.)If you are not very familiar with struct and class, don't worry about it. We can just use them
as if they are simple data types.
Here is how we can declare variables of type Int, Double and String:
y Int16 age, employee Number;
y Double salary;
y String name, address;
we can use any of the .NET data types directly in any .NET language - in C#, VB.NET or
xyz. NET. But in addition to the .NET types, each language provides a set of primitivetypes, which map to the corresponding types in .NET class library. This is why we may see
some people use string and some others use String. There is no big difference. string is aprimitive data type in C# and String is the corresponding class in .NET class library. The
string in C# is mapped to the class in .NET class library. So, whether we use string orString, there is no real difference.
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Data Types in C# and the corresponding class/struct in .NET class library
The following list shows the list of data types available in C# and their corresponding
class/struct in .NET class library.
C# Data type Mapped to .NET class/struct
sbyte System.SByte
byte System.Byte
char System.Char
float System.Single
decimal System.Decimal
double System.Double
ushort System.UInt16
short System.Int16
uint System.UInt32
int System.Int32
ulong System.UInt64
long System.Int64
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bool System.Boolean
string System.String
object System.Object
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Classes and Object Model in .NET
Classes and Object Model in .NET
We will start with an introduction to what is object oriented programming, how to write
simple classes, creating objects etc.
What is a class?
In modern object oriented programming, large computer programs are divided into several'classes'. Typically, a large project will have several hundred classes. A class represents an
entity in a program.
For example, if we are doing a small program called calculator, we will typically have asingle (or more) class called 'Calculator' .The class will have several methods that will do
the functionality of the class
So, our calculator may have methods like the following:
y Add ()
y Subtract ()
y Multiply ()
y Divide ()
Here is a sample calculator class, written in C# :
using System;
public class Calculator
{
public int Add(int value1, int value2)
{
return value1 + value2;
}
public int Subtract(int value1, int value2)
{
return value1 - value2;
}
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public int Multiply(int value1, int value2)
{
return value1 * value2;
}
public int Divide(int value1, int value2)
{
return value1 / value2;
}
}
Methods
Any class in an object-oriented language has method and property members. These are the
places where the actual business logic or functionality is written and executed. Method isobject-oriented item of any language. All C# programs are constructed from a number of
classes and almost all the classes will contain methods. A class when instantiated is called anobject. Object-oriented concepts of programming say that the data members of each object
represent its state and methods represent the object behavior.
Method Signature in C#: Each method is declared as follows:
Return-type methodname ( Parameterslist );
For better understanding of methods let consider following example. We have a class Man. Itcan have many fields like that:
public class Man
{
public Man(){}
private int m_old;
private string m_name;
public string WhatIsYourName()
{
Console.WriteLine(m_name);
return m_name;
}
public string HowOldAreYou()
{
Console.WriteLine(m_old.ToString());
return m_old;
}
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example for the declaration of a function with variable argument signature is as follows.
Public void functionName(int a, params int[] varParam);
Property in C# class
Property in C# class
How do we access member variables of any class from outside the class? In most of the
languages including C++, we will make the member variables public so that we can
create an instance of the class and directly access the public fields, as shown below:
using System;class Hello
{
static void Main () {
Console.WriteLine("hello, world");
}
}
The above class has one public field: color. We may access this field from outside theclass as shown below:
Car car = new Car ();
car. Color = "red";
string color = car.color;
But this is the old way ! This would still work with C#, but the suggested approach is to
use "Property" instead of directly accessing member variables.
The following code snippet shows how to create "Property" in a class.
public class Car
{
// private fields.
private string color;
// constructor
public Car()
{
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}
public string Color
{
get
{
return color; // return the value from privte field.
}
set
{
color = value; // save value into private field.
}
}
}
The above class has one private field - color. Then we have one "Property" called'Color', which is used to represent the private field. Note that the field is private and the
Property is public. (We have used the same name with upper/lower case to represent the'Property' and 'field', but we may give any name we want.)
Each property has two parts:
y get
y set
The get part is executed when we access the value of the Property as shown below:
Car car = new Car();
string color = car.Color;
When executed, the above get accessor will return the value stored in the field 'color'.
The set part is executed when we assign a value to the Property as shown below:
Car car = new Car();
car.Color = "RED
";
When executed, the above set accessor will assign the value "RED" to the private field
'color'. (Note that 'value' is a keyword, which will have the value assigned to it.)
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So, what is the difference ?
On the first look, there is no difference! We can achieve the same behaviour by writing
2 different methods ( like SetColor(...), GetColor() ).
First advantage of using property is, code looks cleaner than having 2 separate methods.
We can simply call a property as if it was a field in the class.
Well, then we may ask why make it 2 methods, we can make it a public field, so that we
can access it by creating an instance of the class.
The main advantage over using a Property instead of a public field is, with the property,we will get a chance to write few lines of code (if we want) in the get and set accessors.
So, we can perform some validation or any other logic before returning any values orassigning to the private field. See the modified class below:
public class Car{
// private fields.
private string color;
// constructor
public Car()
{
}
public string Color
{
get
{
if ( color == "" )
return "GREEN";
else
return color;
}
set
{
if ( value == "" )thrown new Exception ("Wrong value.");
else
color = value;
}
}
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}
Let us analyze the get part first. Here we are checking whether there is a valid value in
the field 'color' before we return the value. If it is empty, we are getting a chance to
return a default value 'Green'. This way, we can make sure that whoever calls theproperty 'Color' will always get a valid color, never an empty string.
In the set part, we are doing a validation to make sure we always assign a a valid value
to our field. If someone assign an empty string to the 'Color' property, he will get an
exception (error).
Car car = new Car();
car.Color = "";
The above code will throw an error because we are trying to assign an empty string and
the set accessor will throw an error if it an empty string. This way, we can make surethat we allow only valid values to be assigned.
So, i guess now you would appreciate the purpose of "Property". So, no more public
fields! Always have private fields and write public properties as wrapper for them if
required to expose them to outside the class.
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Arrays
Arrays
C# arrays are reference types. The size of the array is not part of the array type
int[] row;
int[,] grid;
Array instances are created using the new keyword. Array elements are default
initialised to zero (enums and numeric types), false (bool), or null (reference types).
row = new int[42];
grid = new int[9,6];
Array instances can be initialised:
int[] row = new int[4]{ 1, 2, 3, 4 }; // longhand
int[] row = { 1, 2, 3, 4 }; // shorthand
row = new int[4]{ 1, 2, 3, 4 }; // okay
row = { 1, 2, 3, 4 }; // compile time error
Array indexes start at zero and all array accesses are bounds checked
(IndexOutOfRangeException). All arrays implicitly inherit from the System.Array
class. This class brings array types into the CLR and provides some handy properties
and methods:
namespace System
{
public abstract class Array : .
.. {
...
public int Length { get { ... } }public int Rank { get { ... } }
public int GetLength(int rank) { ... }
public virutal IEnumerator GetEnumerator() { ... }
...
}
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}
Whatare Jagged Arrays in C#?
A special type of array is introduced in C#. A Jagged Array is an array of an array in
which the length of each array index can differ.
Example: A Jagged Array can be used is to create a table in which the lengths of the
rows are not same. This Array is declared using square brackets ( [ ] ) to indicate eachdimension.
The following code demonstrates the creation of a two-dimensional jagged array.
Class Jagged
{
public static void Main()
{
int [][] jagged=new int [3][];
jagged[0]=mew int[4]
jagged[1]=mew int[3]
jagged[2]=mew int[5]
int I;
Storing values in first array
for (I=0;I
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for (I=0;I
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Method Overloading
Method Overloading
In complex applications written in C#, we may need many methods which do
essentially similar functions but are just different enough to be considered unique.
For example, we may have to calculate a person's tax liability and would need to
implement a method for doing this calculation in our application program.
However, there are many different rules when it comes to tax calculations and
they vary throughout the world. While there may be many rules, one basic
equation stays the same: Your net income equals your gross income minus a
computed tax amount. We would probably have to implement different methods
for each type of tax calculation. And, we could give each method a unique name
such as TaxCalc1, TaxCalc2, TaxCalc3, etc. But wouldn't it be nice to just name
the method TaxCalc and pass different arguments to it based on the computationdesired?
Syntax:
Public void functionName(int a, params int[] varParam);
Public void functionName(int a);
How does C# know which method to call? It's easy. It knows which method to
invoke based on the number and type of arguments passed to it. This is also
referred to as the signature of the method. If C# sees you are calling TaxCalc withfour arguments, then it will call that method with four receiving arguments. The
methods are all very similar however they are differ by the number of arguments
used in the tax calculation.
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Caveat
It is important to remember that C# determines which method to call based upon
the method's signature. If you were to define two methods with the same name
and the same number and type of passed arguments, you would get a compile-time error .
However, we can have two methods with the same name and the same number ofarguments as long as the argument types differ.
Method overloading is a powerful concept in C# in that it helps to simplify code
reusability and clarity. If our example method of TaxCalc was placed in a .dll file
somewhere, we would only have to remember that I have to call TaxCalc and only
fill in the appropriate arguments to pass.
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Net C# Tutorial Namespaces
Net C# Tutorial Namespaces
A Namespace in Microsoft .Net is like containers of objects. They may containunions, classes, structures, interfaces, enumerators and delegates. Main goal of
using namespace in .Net is for creating a hierarchical organization of program.
In this case a developer does not need to worry about the naming conflicts of
classes, functions, variables etc., inside a project.
In Microsoft .Net, every program is created with a default namespace. Thisdefault namespace is called as global namespace. But the program itself can
declare any number of namespaces, each of them with a unique name. Theadvantage is that every namespace can contain any number of classes, functions,
variables and also namespaces etc., whose names are unique only inside the
namespace. The members with the same name can be created in some other
namespace without any compiler complaints from Microsoft .Net.
To declare namespace C# .Net has a reserved keyword namespace. If a new
project is created in Visual Studio .NET it automatically adds some global
namespaces. These namespaces can be different in different projects. But each
of them should be placed under the base namespace System. The names space
must be added and used through the using operator, if used in a different project.
using System;
namespace OutNamespace
{
namespace WorkNamespace
{ /// can be placed some classes, structures etc.
}
}
this example we create two namespaces. These namespaces have hierarchical
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structure. We have some outer one named OutNamespace and the inner one
called WorkNamespace. The inner namespace is declared with a C# .Net classWorkItem.
Eliminating the Time Wasters
The Time-wasters will surround you all the sides and will tear away at your
minutes and hours, holding the back from producing a critical results which are
vital to the success in the career.
y Eliminate a time wasters in life;
y The Law of an Excluded Alternative;
y Identify a major time-wasters;
y Practical ways to overcome and avoid them if possible.
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Interfaces
Interfaces
An Interface is a reference type and it contains only abstract members.
Interface's members can be Events, Methods, Properties and Indexers. But the
interface contains only declaration for its members. Any implementation must be
placed in class that realizes them. The interface can't contain constants, data fields,
constructors, destructors and static members. All the member declarations inside
interface are implicitly public.
Defining an Interface:
Let us look at a simple example for c# interfaces. In this example interface
declares base functionality of node object.
interface INode
{
string Text
{
get;
set;
}
object Tag
{
get;set;
}
int Height
{
get;
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set;
}
int Width
{get;
set;
}
float CalculateArea();
}
The above INode interface has declared a few abstract properties and function
which should be implemented by the derived classes.
Sample for Deriving a class using a C# .Net interface
public class Node : INode
{
public Node()
{}
public string Text
{
get
{
return m_text;
}
set
{
m_text = value;
}
}
private string m_text;
public object Tag{
get
{
return m_tag;
}
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set
{
m_tag = value;
}}
private object m_tag = null;
public int Height
{
get
{
return m_height;
}
set{
m_height = value;
}
}
private int m_height = 0;
public int Width
{
get
{
return m_width;
}
set
{
m_width = value;
}
}
private int m_width = 0;
public float CalculateArea()
{
if((m_width
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Now the above code has created a c# class Node that inherits from INode c#
interface and implement all its members. A very important point to be
remembered about c# interfaces is, if some interface is inherited, the program
must implement all its declared members. Otherwise the c# compiler throws an
error.
The above code was a simple example of c# interface usage. Now this has to
be followed with some advanced details of interface building in C# .Net. The
previous example used only names of methods or properties that have the same
names as in interface. But there is another alternative method for writing the
implementation for the members in class. It uses full method or property name
.
Multiple Inheritance using C# interfaces:
Next feature that obviously needs to be explained is multiple inheritance using
c# interfaces. This can be done using child class that inherits from any number
of c# interfaces. The inheritance can also happen with a combination of a C#.Net class and c# interfaces. Now let us see a small piece of code that
demonstrate us multiple inheritance using only interfaces as parent data types
class ClonableNode : INode,ICloneable
{
public object Clone()
{
return null;
}
// INode members
}
The above example created a class ClonableNode. It implements all the
functionality of INode interface in the same way as it was done in Node class.
Also it realizes Clone method only one item of IClonable interface of .NET
library.
is Operator for C# .Net interfaces -
At last a new C# operator that can be used to define that class should be
explained. It is the is operator. Look at the following piece of code:
if(nodeC is INode)
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Console.WriteLine("nodeC is object of INode type");
else
Console.WriteLine("nodeC isn't object of INode type");
In example nodeC object was created as ClonableNode type, but when we run
program "if operator" returns true. It means that nodeC also is of INode type.
Delegates in C#
Delegates in C# .Net:
If we look at C++ there is a feature called callback function.
This feature uses Pointers to Functions to pass them as parameters to other
functions. Delegate is a similar feature but it is more type safe, which stands as a
stark contrast with C++ function pointers. A delegate can hold reference/s to one
more more functions and invoke them as and when needed.
A delegate needs the method's name and its parameters (input and output
variables) when we create a delegate. But delegate is not a standalone
construction. it's a class. Any delegate is inherited from base delegate class of
.NET class library when it is declared. This can be from either of the twoclasses from System.Delegate or System. MulticastDelegate.
If the delegate contains a return type of void, then it is automatically aliased tothe type of System.MulticastDelegate. This can support multiple functions
with a += operator. If the delegate contains a non-void return type then it isaliased to System. Delegate class and it cannot support multiple methods.
Let us have alookat the following sample code.
class Figure
{
public Figure(float a, float b, float c)
{
m_xPos = a;
m_yPos = b;
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m_zPos = c;
}
public void InvertX()
{m_xPos = - m_xPos;
}
public void InvertY()
{
m_yPos = - m_yPos;
}
public void InvertZ()
{
m_zPos = - m_zPos;
}
private float m_xPos = 0;
private float m_yPos = 0;
private float m_zPos = 0;
}
Now, we have a class named Figure and it has three private fields that use to
store position and three methods to invert this position by every axis. In main
class we declare delegate as follows:
public delegate void FigureDelegate();
And now in the main function we should use it like this:
Figure figure = new Figure(10,20,30);
FigureDelegate fx = new FigureDelegate(figure.InvertX);
FigureDelegate fy = new FigureDelegate(figure.InvertY);
FigureDelegate fz = new FigureDelegate(figure.InvertZ);
MulticastDelegate f_del = fx+fy+fz;
In this example we create three delegates of FigureDelegate type and attach to
these elements our three methods from Figure class. Now every delegate keeps
the address of the attached function. The last line of code is very interesting,here we create a delegate of base type (MulticastDelegate) and attach three of
our already created delegates. As all our methods are of void return type they
are automatically of type MutlticastDelegate and a MulticastDelegate can
support multiple methods invocation also. Hence we can write
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Figure figure = new Figure(10,20,30);
FigureDelegate fMulti = new FigureDelegate(figure.InvertX);
fMulti += new FigureDelegate(figure.InvertY);fMulti();
Events in C# .Net
Events in C# .Net:
Delegate usefulness does not just lie in the fact that it can hold the
references to functions but in the fact that it can define and use functionnames at runtime and not at compile time.
A large goal of design delegates is their applicability in events model of .Net.
Events are the actions of the system on user manipulations (e.g. mouse clicks,
key press, timer etc.) or any event triggered by the program. To understand the
usage of delegates for event model, the previous examples are used here. We
should add to our Figure class next things:
public delegate void FigureHandler(string msg);
public static event FigureHandler Inverted;
public void InvertZ()
{
m_zPos = - m_zPos;
Inverted("inverted by z-axis");
}
Now we have a delegate declared and event that uses this delegate's type.
In every function we should call our event. The next code snippet should
explain it clearly
static void Main(string[] args){
Figure figure = new Figure(10,20,30);
Figure.Inverted+=new Test.Figure.FigureHandler(OnFigureInverted);
figure.InvertX();
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figure.InvertZ();
}
private static void OnFigureInverted(string msg)
{
Console.WriteLine("Figure was {0}",msg);
}
So, in the main function we should create an object of figure class and
attach event handler to the method OnFigureInverted. And when we callany of invert methods the event is fired and it calls our event handler. The
application will print the following string into the console: Figure wasinverted by x-axis Figure was inverted by z-axis .
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