C# – Type Conversion

Type conversion is converting one type of data to another type. It is also known as Type Casting. In C#, type casting has two forms −

Implicit type conversion − These conversions are performed by C# in a type-safe manner. For example, 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 −

using System;

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 the following result −

5673

Encapsulation

Encapsulation is defined ‘as the process of enclosing one or more items within a physical or logical package’. Encapsulation, in object oriented programming methodology, prevents access to implementation details.

Abstraction and encapsulation are related features in object oriented programming. Abstraction allows making relevant information visible and encapsulation enables a programmer to implement the desired level of abstraction.

Encapsulation is implemented by using access specifiers. An access specifier defines the scope and visibility of a class member. C# supports the following access specifiers −

  • Public
  • Private
  • Protected
  • Internal
  • Protected internal

Public Access Specifier

Public access specifier allows a class to expose its member variables and member functions to other functions and objects. Any public member can be accessed from outside the class.

The following example illustrates this −

using System;

namespace RectangleApplication {
class Rectangle {
//member variables
public double length;
public double width;

public double GetArea() {
return length * width;
}
public void Display() {
Console.WriteLine(“Length: {0}”, length);
Console.WriteLine(“Width: {0}”, width);
Console.WriteLine(“Area: {0}”, GetArea());
}
}//end class Rectangle

class ExecuteRectangle {
static void Main(string[] args) {
Rectangle r = new Rectangle();
r.length = 4.5;
r.width = 3.5;
r.Display();
Console.ReadLine();
}
}
}

In the preceding example, the member variables length and width are declared public, so they can be accessed from the function Main() using an instance of the Rectangle class, named r.

The member function Display() and GetArea() can also access these variables directly without using any instance of the class.

The member functions Display() is also declared public, so it can also be accessed from Main() using an instance of the Rectangle class, named r.

Private Access Specifier


Private access specifier allows a class to hide its member variables and member functions from other functions and objects. Only functions of the same class can access its private members. Even an instance of a class cannot access its private members.

The following example illustrates this −

using System;

namespace RectangleApplication {
class Rectangle {
//member variables
private double length;
private double width;

public void Acceptdetails() {
Console.WriteLine("Enter Length: ");
length = Convert.ToDouble(Console.ReadLine());
Console.WriteLine("Enter Width: ");
width = Convert.ToDouble(Console.ReadLine());
}
public double GetArea() {
return length * width;
}
public void Display() {
Console.WriteLine("Length: {0}", length);
Console.WriteLine("Width: {0}", width);
Console.WriteLine("Area: {0}", GetArea());
}
}//end class Rectangle

class ExecuteRectangle {
static void Main(string[] args) {
Rectangle r = new Rectangle();
r.Acceptdetails();
r.Display();
Console.ReadLine();
}
}
}

C# – Methods

A method is a group of statements that together perform a task. Every C# program has at least one class with a method named Main.

To use a method, you need to −

  • Define the method
  • Call the method

Defining Methods in C#
When you define a method, you basically declare the elements of its structure. The syntax for defining a method in C# is as follows −

<Access Specifier> <Return Type> <Method Name>(Parameter List) {
Method Body
}

Following are the various elements of a method −

Access Specifier − This determines the visibility of a variable or a method from another class.

Return type − A method may return a value. The return type is the data type of the value the method returns. If the method is not returning any values, then the return type is void.

Method name − Method name is a unique identifier and it is case sensitive. It cannot be same as any other identifier declared in the class.

Parameter list − Enclosed between parentheses, the parameters are used to pass and receive data from a method. The parameter list refers to the type, order, and number of the parameters of a method. Parameters are optional; that is, a method may contain no parameters.

Method body − This contains the set of instructions needed to complete the required activity.

Example
Following code snippet shows a function FindMax that takes two integer values and returns the larger of the two. It has public access specifier, so it can be accessed from outside the class using an instance of the class.

class NumberManipulator {

public int FindMax(int num1, int num2) {
/* local variable declaration */
int result;

if (num1 > num2)
result = num1;
else
result = num2;

return result;
}
...
}

Calling Methods in C#
You can call a method using the name of the method. The following example illustrates this −
using System;

namespace CalculatorApplication {
class NumberManipulator {
public int FindMax(int num1, int num2) {
/* local variable declaration */
int result;

if (num1 > num2)
result = num1;
else
result = num2;
return result;
}

static void Main(string[] args) {
/* local variable definition */
int a = 100;
int b = 200;
int ret;
NumberManipulator n = new NumberManipulator();

//calling the FindMax method
ret = n.FindMax(a, b);
Console.WriteLine("Max value is : {0}", ret );
Console.ReadLine();
}
}
}

When the above code is compiled and executed, it produces the following result −

Max value is : 200
You can also call public method from other classes by using the instance of the class. For example, the method FindMax belongs to the NumberManipulator class, you can call it from another class Test.

Live Demo
using System;

namespace CalculatorApplication {
class NumberManipulator {
public int FindMax(int num1, int num2) {
/* local variable declaration */
int result;

if(num1 > num2)
result = num1;
else
result = num2;

return result;
}
}
class Test {
static void Main(string[] args) {
/* local variable definition */
int a = 100;
int b = 200;
int ret;
NumberManipulator n = new NumberManipulator();

//calling the FindMax method
ret = n.FindMax(a, b);
Console.WriteLine(“Max value is : {0}”, ret );
Console.ReadLine();
}
}
}
When the above code is compiled and executed, it produces the following result −

Max value is : 200
Recursive Method Call
A method can call itself. This is known as recursion. Following is an example that calculates factorial for a given number using a recursive function −

Live Demo
using System;

namespace CalculatorApplication {
class NumberManipulator {
public int factorial(int num) {
/* local variable declaration */
int result;
if (num == 1) {
return 1;
} else {
result = factorial(num – 1) * num;
return result;
}
}
static void Main(string[] args) {
NumberManipulator n = new NumberManipulator();
//calling the factorial method {0}”, n.factorial(6));
Console.WriteLine(“Factorial of 7 is : {0}”, n.factorial(7));
Console.WriteLine(“Factorial of 8 is : {0}”, n.factorial(8));
Console.ReadLine();
}
}
}
When the above code is compiled and executed, it produces the following result −

Factorial of 6 is: 720
Factorial of 7 is: 5040
Factorial of 8 is: 40320
Passing Parameters to a Method
When method with parameters is called, you need to pass the parameters to the method. There are three ways that parameters can be passed to a method −

Sr.No. Mechanism & Description
1 Value parameters
This method copies the actual value of an argument into the formal parameter of the function. In this case, changes made to the parameter inside the function have no effect on the argument.

2 Reference parameters
This method copies the reference to the memory location of an argument into the formal parameter. This means that changes made to the parameter affect the argument.

3 Output parameters
This method helps in returning more than one value.