C# Dot net unit-2.pdf

C# and Dot Net Framework
Part-2
Dr. K ADISESHA

Introduction
Overview of C#
C# Program Structure
OOPS with C#
Arrays
2
Introduction to C#
Prof. K. Adisesha
Prof. K. Adisesha

Introduction
Prof. K. Adisesha
3
C# (C-Sharp) :
C# (C-Sharp) is object-oriented programming language created by Microsoft that runs
on the .NET Framework.
➢ C# has roots from the C family, and the language is close to other popular languages
like C++ and Java.
➢ C# is used for developing:
❖ Mobile applications
❖ Desktop applications
❖ Web applications
❖ Web services
❖ Games
❖ Database applications

Introduction
Prof. K. Adisesha
4
C# IDE:
C# uses Visual Studio IDE (Integrated Development Environment) to edit and compile
code.

Introduction
Prof. K. Adisesha
5
C# IDE:
Using Visual Studio.Net IDE 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 click OK button.
➢ This creates a new project in Solution Explorer.
➢ Write code in the Code Editor.
➢ Click the Run button or press F5 key to execute the project.

Introduction
Prof. K. Adisesha
6
C# program structure:
A C# program consists of the following parts:
➢ Namespace declaration
➢ A class
➢ Class methods
➢ Class attributes
➢ A Main method
➢ Statements and Expressions
➢ Comments

C# program
Prof. K. Adisesha
7
C# program Structure:
➢ C# Comments: Comments can be used to explain C# code, and to make it more
readable. It can also be used to prevent execution when testing alternative code.
❖ Single-line comments start with two forward slashes (//).
❖ Multi-line comments start with /* and ends with */. (will not be executed).
➢ C# Identifiers: Identifiers are descriptive names in order to create understandable and
maintainable code.
➢ The general rules for naming Identifiers/variables are:
❖ Names can contain letters, digits and the underscore character (_)
❖ Names must begin with a letter
❖ Names should start with a lowercase letter and it cannot contain whitespace
❖ Names are case sensitive ("myVar" and "myvar" are different variables)
❖ Reserved words (like C# keywords, such as int or double) cannot be used as names

C# program
Prof. K. Adisesha
8
➢ C# Variables: Variables are containers for storing data values. All C# variables must
be identified with unique names.
❖ Syntax: type variableName = value;
❖ Example: string name = “K. Adisesha";
int x = 5, y = 6, z = 50;
➢ C# Constants: The const keyword is useful when you want a variable to always store
the same value. Example: const int Num = 15;
Num = 20; // error
➢ Display Variables: The WriteLine() method is often used to display variable values to
the console window. To combine both text and a variable, use the + character:
Example: string name = "John";
Console.WriteLine("Hello " + name);

Data Type Size Description
Int 4 bytes Stores whole numbers from -2,147,483,648 to 2,147,483,647
long 8 bytes Stores whole numbers from -/+9,223,372,036,854,775,808
float 4 bytes Stores fractional numbers. Sufficient for storing 6 to 7 decimal digits
double 8 bytes Stores fractional numbers. Sufficient for storing 15 decimal digits
bool 1 bytes Stores true or false values
char 2 bytes Stores a single character/letter, surrounded by single quotes
string 2 bytes per character Stores a sequence of characters, surrounded by double quotes
C# program
Prof. K. Adisesha
9
C# Data Types: A data type specifies the size and type of variable values. It is important
to use the correct data type for the corresponding variable to save time and memory.
➢ The most common data types are:

C# Programming
Prof. K. Adisesha
10
C# Type Casting: Type casting is when you assign a value of one data type to another type.
➢ In C#, there are two types of casting:
➢ Implicit Casting (automatically) - converting a smaller type to a larger type size
❖ char -> int -> long -> float -> double
❖ Example: int myInt = 9;
double myDouble = myInt; // Automatic casting: int to double
➢ Explicit Casting (manually) - converting a larger type to a smaller size type
➢ It must be done manually by placing the type in parentheses in front of the value:
❖ double -> float -> long -> int -> char
❖ Example: double myDouble = 9.78;
int myInt = (int) myDouble; // Manual casting: double to int

C# Programming
Prof. K. Adisesha
11
Type Conversion Methods: It is also possible to convert data types explicitly by using built-
in methods,
➢ In C#, there are various built-in methods for types conversion:
❖ Convert.ToBoolean Example:
❖ Convert.ToDouble
❖ Convert.ToString
❖ Convert.ToInt32 (int)
❖ Convert.ToInt64 (long)
int myInt = 10;
double myDouble = 5.25;
bool myBool = true;
Console.WriteLine(Convert.ToString(myInt)); // convert int to string
Console.WriteLine(Convert.ToDouble(myInt)); // convert int to double
Console.WriteLine(Convert.ToInt32(myDouble)); // convert double to int
Console.WriteLine(Convert.ToString(myBool)); // convert bool to string

C# Programming
Prof. K. Adisesha
12
C# User Input/output: The user can input or display output his or hers data, which is
stored in the variable using built-in methods.
User Input:The Console.ReadLine() method returns a string.
❖ // Create a string variable and get user input from the keyboard and store it in the variable
string userName = Console.ReadLine();
User Output:Console.WriteLine() is used to output (print) values..
❖ // Print the value of the variable (userName), which will display the input value
Console.WriteLine("Username is: " + userName);
❖ Example: Console.WriteLine("Enter your age:");
int age = Convert.ToInt32(Console.ReadLine());
Console.WriteLine("Your age is: " + age);

C# Programming
Prof. K. Adisesha
13
C# - Operators: An operator is a symbol that tells the compiler to perform specific
mathematical or logical manipulations.
➢ C# has rich set of built-in operators and provides the following type of operators.
❖ Arithmetic Operators
❖ Relational Operators
❖ Logical Operators
❖ Bitwise Operators
❖ Assignment Operators
❖ Misc Operators

C# Programming
Prof. K. Adisesha
14
C# - Operators:
Arithmetic Operators: Following table shows all the arithmetic operators supported by C#.
➢ Assume variable A holds 10 and variable B holds 20 then −.
Operator Description Example
+ Adds two operands A + B = 30
- Subtracts second operand from the first A - B = -10
* Multiplies both operands A * B = 200
/ Divides numerator by de-numerator B / A = 2
% Modulus Operator and remainder of after an integer division B % A = 0
++ Increment operator increases integer value by one A++ = 11
-- Decrement operator decreases integer value by one A-- = 9

== Checks if the values of two operands are equal or not, if yes then condition becomes
true.
(A == B) is false
!= Checks if the values of two operands are equal or not, if values are not equal then
condition becomes true.
(A != B) is true.
> Checks if the value of left operand is greater than the value of right operand (A > B) is false
< Checks if the value of left operand is less than the value of right operand (A < B) is true.
>= Checks if the value of left operand is greater than or equal to the value of right operand (A >= B) is false
<= Checks if the value of left operand is less than or equal to the value of right operand, (A <= B) is true.
C# Programming
Prof. K. Adisesha
15
C# - Operators:
Relational Operators: Following table shows all the relational operators supported by C#.

== Checks if the values of two operands are equal or not, if yes then condition becomes
true.
(A == B) is false
!= Checks if the values of two operands are equal or not, if values are not equal then
condition becomes true.
(A != B) is true.
> Checks if the value of left operand is greater than the value of right operand (A > B) is false
< Checks if the value of left operand is less than the value of right operand (A < B) is true.
>= Checks if the value of left operand is greater than or equal to the value of right operand (A >= B) is false
<= Checks if the value of left operand is less than or equal to the value of right operand, (A <= B) is true.
C# Programming
Prof. K. Adisesha
16
C# - Operators:
Relational Operators: Following table shows all the relational operators supported by C#.

C# Programming
Prof. K. Adisesha
17
C# - Operators:
Logical Operators: Following table shows all the logical operators supported by C#.
➢ Assume variable A holds Boolean value true and variable B holds value false, then:
&& Called Logical AND operator. If both the operands are non zero then condition
becomes true.
(A && B) is false.
|| Called Logical OR Operator. If any of the two operands is non zero then condition
becomes true.
(A || B) is true.
! Called Logical NOT Operator. Use to reverses the logical state of its operand. If a
condition is true then Logical NOT operator will make false.
!(A && B) is true.
Bitwise Operators: Bitwise operator works on bits and perform bit by bit operation.
➢ The Bitwise operator supported by C# are: “ &, |, ~ , ^ , >> , << ”

C# Programming
Prof. K. Adisesha
18
C# - Operators:
Miscellaneous Operators: There are few other important operators including sizeof, typeof
and ? : supported by C#.
sizeof() Returns the size of a data type. sizeof(int), returns 4.
typeof() Returns the type of a class. typeof(StreamReader);
& Returns the address of an variable. &a; returns actual address of the variable.
* Pointer to a variable. *a; creates pointer named 'a' to a variable.
? : Conditional Expression If Condition is true ? Then value X : Otherwise value Y
is Determines whether an object is of a
certain type.
If( Ford is Car) // checks if Ford is an object of the Car
class.
as Cast without raising an exception if the
cast fails.
Object obj = new StringReader("Hello");StringReader r
= obj as StringReader;

C# Programming
Prof. K. Adisesha
19
C# - Control Structures:
Conditional statements: There are few conditions statements to perform different actions
for different decisions that are supported by C#.
➢ C# has the following conditional statements:
❖ if :Use if to specify a block of code to be executed, if a specified condition is true
❖ else : Use else to specify a block of code to be executed, if the same condition is false
❖ else if :Use else if to specify a new condition to test, if the first condition is false
❖ Switch : Use switch to specify many alternative blocks of code to be executed
Example
if (30 > 18)
{
Console.WriteLine(“30 is greater than 18");
}

C# Programming
Prof. K. Adisesha
20
Short Hand If...Else (Ternary Operator): short-hand if else, which is known as the ternary
operator because it consists of three operands.
➢ It can be used to replace multiple lines of code with a single line.
➢ It is often used to replace simple if else statements:
Syntax: variable = (condition) ? expressionTrue : expressionFalse;
Example
int Percentage = 60;
if (time < 35)
{ Console.WriteLine(“First class"); }
else
{ Console.WriteLine(“Fail."); }
int Percentage = 60;
string result = (Percentage < 35) ? “First Class." : “Fail";
Console.WriteLine(result);
Example :Ternary Operator

C# Programming
Prof. K. Adisesha
21
Switch Statements : Use the switch statement to select one of many code blocks to be
executed.
➢ The switch expression is evaluated once
➢ The value of the expression is compared with the values of each case
➢ If there is a match, the associated block of code is executed:
Example
switch(expression)
{
case x:
// code block
break;
case y:
// code block
break;
default:
// code block
break; }

C# Programming
Prof. K. Adisesha
22
C# - Loops: Loops can execute a block of code as long as a specified condition is reached.
➢ C# provides following types of loop to handle looping requirements.
Loop Type Description
while loop It repeats a statement or a group of statements while a given condition is true.
It tests the condition before executing the loop body.
for loop It executes a sequence of statements multiple times and abbreviates the code that
manages the loop variable.
do...while loop It is similar to a while statement, except that it tests the condition at the end of the
loop body
nested loops You can use one or more loop inside any another while, for or do..while loop.

C# Programming
Prof. K. Adisesha
23
C# - Loops:
➢ C# For Loop: When you know exactly how many times you want to loop through a
block of code, use the for loop instead of a while loop.
❖ Syntax : for (statement 1; statement 2; statement 3)
{ // code block to be executed }
➢ foreach Loop: There is also a foreach loop, which is used exclusively to loop through
elements in an array:
❖ Syntax : foreach (type variableName in arrayName)
{
// code block to be executed
}
Example
for (int i = 0; i < 5; i++)
{ Console.WriteLine(i);
}
Example
string[] Course = {"BCA", "BCom",
"BBA", "BHM"};
foreach (string i in Course)
{ Console.WriteLine(i);
}

C# Programming
Prof. K. Adisesha
24
C# - Arrays:
An array stores a fixed-size sequential collection of elements of the same type.
➢ To declare an array in C#, you can use the following syntax −
❖ Syntax : datatype[] arrayName;
➢ Array is a reference type, so you need to use the new keyword to create an instance of the
array.
❖ Example : double[] balance = new double[10];
➢ You can also create and initialize an array, as shown −
❖ Example : int [] marks = new int[5] { 99, 98, 92, 97, 95};
➢ You can copy an array variable into another target array variable. In such case, both the
target and source point to the same memory location −
❖ Example: int [] marks = new int[] { 99, 98, 92, 97, 95};
int[] score = marks;

C# Programming
Prof. K. Adisesha
25
Multidimensional Arrays:
A multidimensional array is basically an array of arrays which can have any number of
dimensions. The most common are two-dimensional arrays (2D).
➢ The single comma [,] specifies that the array is two-dimensional. A three-dimensional
array would have two commas: int[,,].
➢ To create a 2D array, add each array within its own set of curly braces, and insert a
comma (,) inside the square brackets.
❖ Syntax : int[,] numbers = { {1, 2, 3}, {10, 20, 30} };
➢ To access an element of a two-dimensional array, you must specify two indexes.
❖ Example : int[,] numbers = { {1, 2, 3}, {10, 20, 30} };
Console.WriteLine(numbers[0, 2]); // Outputs 3

C# Programming
Prof. K. Adisesha
26
C# Methods / Functions:
A method is a block of code which only runs when it is called.You can pass data, known as
parameters, into a method.
➢ Methods are used to perform certain actions, and they are also known as functions.
➢ A method is defined with the name of the method, followed by parentheses ().
➢ C# provides some pre-defined methods, such as Main().
❖ Create a method inside the Program class:
class Program
{ static void MyMethod()
{ // code to be executed }
}
static void MyMethod()
{ Console.WriteLine(“Hello Sunny!");
}
static void Main(string[] args)
{ MyMethod();
}
Outputs : Hello Sunny!

C# Programming
Prof. K. Adisesha
27
C# Methods / Functions:
Parameters and Arguments: Information can be passed to methods as parameter.
Parameters act as variables inside the method.
➢ They are specified after the method name, inside the parentheses. You can add as many
parameters as you want, just separate them with a comma.
➢ Example:
static void MyMethod(string fname, int age)
{ Console.WriteLine(fname + " is " + age);
}
{ MyMethod(“Adi”, 48);
MyMethod(“Prajwal", 18);
MyMethod(“Sunny", 16); }
Outputs : Adi is 48
Prajwal is 18
Sunny is 16

C# Programming
Prof. K. Adisesha
28
C# OOP:
OOP stands for Object-Oriented Programming, which is about creating objects that
contain both data and methods.
➢ Object-oriented programming has several advantages over procedural programming:
❖ OOP is faster and easier to execute
❖ OOP provides a clear structure for the programs
❖ OOP helps to keep the C# code DRY "Don't Repeat Yourself", and makes the code
easier to maintain, modify and debug
❖ OOP makes it possible to create full reusable applications with less code and shorter
development time

C# Programming
Prof. K. Adisesha
29
C# Object and Class:
C# is an object-oriented language, program is designed using objects and classes in C#.
➢ C# Object: Object is a runtime entity, it is created at runtime. Object is an entity that has
state and behavior. Here, state means data and behavior means functionality.
❖ Example: Student s1 = new Student();//creating an object of Student
➢ C# Class : In C#, class is a group of similar objects. It is a template from which objects
are created. It can have fields, methods, constructors etc.
❖ Let's see an example of C# class that has two fields only.
public class Student
{ int id;//field or data member
String name;//field or data member
}

C# Programming
Prof. K. Adisesha
30
C# - Inheritance:
Inheritance allows us to define a class in terms of another class, which makes it easier to
create and maintain an application.
➢ This also provides an opportunity to reuse the code functionality and speeds up
implementation time.
➢ Base and Derived Classes: A class can be derived from more than one class or interface,
which means that it can inherit data and functions from multiple base classes or
interfaces.
❖ Example: <acess-specifier> class <base_class> //Base class
{ ... }
class <derived_class> : <base_class> //Derived class
{ ... }

C# Programming
Prof. K. Adisesha
31
C# - Polymorphism:
In object-oriented programming paradigm, polymorphism is often expressed as 'one
interface, multiple functions'.
➢ Polymorphism can be static or dynamic.
❖ In static polymorphism, the response to a function is determined at the compile time.
❖ In dynamic polymorphism, it is decided at run-time..
➢ Static Polymorphism: The mechanism of linking a function with an object during compile
time is called early binding. It is also called static binding.
➢ C# provides two techniques to implement static polymorphism:
❖ Function overloading
❖ Operator overloading

C# Programming
Prof. K. Adisesha
32
C# - Polymorphism:
Function overloading: Also called Method overloading, having two or more methods with
same name but different in parameters, is known as method overloading in C#.
➢ You can perform method overloading in C# by two ways:
❖ By changing number of arguments
❖ By changing data type of the arguments.
➢ Example: public class TestMemberOverloading
{ public static void Main( )
{
Console.WriteLine(Cal.add(15, 20));
Console.WriteLine(Cal.add(15, 20, 25));
}
}
using System;
public class Cal
{
public static int add(int a, int b)
{ return a + b; }
public static int add(int a, int b, int c)
{ return a + b + c; }
}

C# Programming
Prof. K. Adisesha
33
C# - Polymorphism:
C# - Operator Overloading: You can redefine or overload most of the built-in operators
available in C#. Thus a programmer can use operators with user-defined types as well.
➢ Overloaded operators are functions with special names the keyword operator followed by
the symbol for the operator being defined. similar to any other function, an overloaded
operator has a return type and a parameter list.
➢ Example, public static Box operator+ (Box b, Box c)
{ Box box = new Box();
box.length = b.length + c.length;
box.breadth = b.breadth + c.breadth;
box.height = b.height + c.height;
return box;
}
❖ function implements the addition operator (+)
for a user-defined class Box. It adds the
attributes of two Box objects and returns the
resultant Box object.

C# Programming
Prof. K. Adisesha
34
C# - Interfaces:
An interface is defined as a syntactical contract that all the classes inheriting the interface
should follow. The interface defines the 'what' part of the syntactical contract and the
deriving classes define the 'how' part of the syntactical contract.
➢ Interfaces define properties, methods, and events, which are the members of the interface.
Interfaces contain only the declaration of the members.
➢ Interfaces are declared using the interface keyword. It is similar to class declaration.
Interface statements are public by default.
➢ Syntax: public interface ITransactions
{ // interface members
void showTransaction();
double getAmount();
}
Example: // Interface
interface Student
{void StudentCourse( ); // interface method (does not have a body) }
class BCA : Student
{ public void StudentCourse( )
{ // The body of StudentCourse( ) is provided here
Console.WriteLine(“BCA Students Study C#"); } }

C# Programming
Prof. K. Adisesha
35
C# - Interfaces:
An interface is defined as a syntactical contract that all the classes inheriting the interface
should follow. The interface defines the 'what' part of the syntactical contract and the
deriving classes define the 'how' part of the syntactical contract.
➢ Like abstract classes, interfaces cannot be used to create objects
➢ Interface methods do not have a body - the body is provided by the "implement" class
➢ On implementation of an interface, you must override all of its methods
➢ Interfaces can contain properties and methods, but not fields/variables
➢ Interface members are by default abstract and public
➢ An interface cannot contain a constructor (as it cannot be used to create objects)

C# Programming
Prof. K. Adisesha
36
C# Enumerations:
An enum is a special "class" that represents a group of constants (unchangeable/read-
only variables).
➢ Enum is short for "enumerations", which means "specifically listed".
➢ To create an enum, use the enum keyword (instead of class or interface), and separate the
enum items with a comma.
➢ By default, the first item of an enum has the value 0. The second has the value 1, and so
on.
➢ Example:
class Program
{
enum Level
{ Low,
Medium,
High
}
//You can access enum items with the dot syntax:
{ Level myVar = Level.Medium;
Console.WriteLine(myVar);
}
}

C# Programming
Prof. K. Adisesha
37
C# - Exception Handling:
An exception is a problem that arises during the execution of a program.
A C# exception is a response to an exceptional circumstance that arises while a program is
running, such as an attempt to divide by zero.
➢ Exceptions provide a way to transfer control from one part of a program to another.
➢ C# exception handling is built upon four keywords:
❖ try
❖ catch
❖ finally
❖ throw
try { // statements causing exception }
catch( ExceptionName e1 ) { // error handling code }
catch( ExceptionName e2 ) { // error handling code }
catch( ExceptionName eN ) { // error handling code }
finally { // statements to be executed }

C# Programming
Prof. K. Adisesha
38
C# - Exception Handling:
A C# exception is a response to an exceptional circumstance that arises while a program is
running, such as an attempt to divide by zero.
➢ try − A try block identifies a block of code for which particular exceptions is activated. It is
followed by one or more catch blocks.
➢ catch − A program catches an exception with an exception handler at the place in a program
where you want to handle the problem. The catch keyword indicates the catching of an exception.
➢ finally − The finally block is used to execute a given set of statements, whether an exception is
thrown or not thrown. For example, if you open a file, it must be closed whether an exception is
raised or not.
➢ throw − A program throws an exception when a problem shows up. This is done using a throw
keyword.

C# Programming
Prof. K. Adisesha
39
C# - File I/O:
A file is a collection of data stored in a disk with a specific name and a directory path.
When a file is opened for reading or writing, it becomes a stream.
➢ The stream is basically the sequence of bytes passing through the communication path.
➢ There are two main streams: the input stream and the output stream.
❖ The input stream is used for reading data from file (read operation).
❖ The output stream is used for writing into the file (write operation).
➢ The File class from the System.IO namespace, allows us to work with files.
➢ Example:
using System.IO; // include the System.IO namespace
File.SomeFileMethod(); // use the file class with methods

Discussion
Prof. K. Adisesha
40
Queries ?
Prof. K. Adisesha
9449081542

C# Dot net unit-2.pdf

More Related Content

What's hot (20)

Similar to C# Dot net unit-2.pdf (20)

More from Prof. Dr. K. Adisesha (20)

Recently uploaded (20)

C# Dot net unit-2.pdf