05 iec t1_s1_oo_ps_session_07

Slide 1 of 32Session 7Ver. 1.0

Object-Oriented Programming Using C#

In this session, you will learn to:Describe memory allocation

Use structure

Use enumerations

Implement arrays

Use collections

Objectives



The memory allocated to variables is referred to in the following ways:

Value types: Contains data. Built-in data types, such as int, char, and float are value types.

Reference types: Contains address referring to a block of memory. Data types, such as string and class are reference types.

Let us understand the concept of memory allocation in detail.

Describing Memory Allocation



Describing Memory Allocation (Contd.)

int Num1;Num1=50;

Initialization

Initializing Num2 with Num1

int Num2;

Num2=Num1;

Variable Declaration

Value Type:

Variable Declaration 50

50

Both Num1 and Num2 Contain 50

Num1

Num2




Value Type (Contd.):

Num1=60;

Num1

60

Num2

50

The Value of Num2 Remains Unaffected

New Value Assigned to Num1



Car Suzuki= new Car();

Suzuki.Model=10;

Object of Class Car()

Member Variable of Class Car()

Initialization

Initializing Mercedes with Suzuki

Object of Class Car()Car Mercedes;

Mercedes=Suzuki;


Reference Type:



Suzuki

Mercedes

***

***

10

Referring to Memory Location Where the Data is Stored

Referring to Memory Location Where the Data is Stored


Reference Type (Contd.):



A structure is a value type data type.

When you want a single variable to hold related data of various data types, you can create a structure.

To create a structure you use the struct keyword.

The following code shows the example of a declaring a structure names Bill_Details:struct Bill_Details

{ public string inv_No; // Invoice Number

string ord_Dt; // Order Date

string custName; // Customer name

Using Structure



public string product; // Product Name

public double cost; // Cost of the product

public double due_Amt; // Total amount due

}

Using Structure (Contd.)



Enumeration is a value type data type.

Enumeration contains its own values and cannot inherit or pass inheritance.

Enumerators allows you to assign symbolic names to integral constants.

To enumerate, you can use the enum keyword.

Using Enumeration



The following code is an example of declaring an enumeration named Days:enum Days { Sat, Sun, Mon, Tue, Wed, Thu, Fri };

Declaring an Enumeration



After declaring the enumeration type, you can use the enumeration type in the same manner as any other data type:int First_Day = (int)Days.Sat;

int Last_Day = (int)Days.Fri;

Implementing Enumerations



Implementing Arrays

An array is a collection of values of the same data type.

The following figure shows the array structure in the system’s memory.

Index

Value 0

Index

Value 6



Declaring an Array

An array needs to be declared before it can be used in a program.

You can declare an array by using the following statement:datatype[] Arrayname;

Let us understand the explanation of the various elements of the array declaration through an example.



Declaring an Array (Contd.)

int[ ] Score; Datatype

Is used to specify the data type for the elements




int[ ] Score; [ ]

Is used to specify the rank of the array




int[ ] Score; Arrayname

Is used to specify the name of the array using which the elements of the array will be initialized and manipulated



In C#, you can initialize the array variable and can assign values to the array elements. In addition, you can copy the array variable to another variable.

During initialization, you need to use the new keyword to create an instance of the array. In addition, the size of the array is also specified while it is initialized.

The following is an example of array initialization:int[] Score; // Array declaration

Score = new int[10]; //Array Instance

Initializing and Assigning Values to Array



You can assign values to each element of the array by using the index number, which is called the array subscript of the element.

The following is an example of assigning values to the array:int[] Score = new int[3];

Score[0]=10;

Orint[] Score={5,10,15};

When you copy the array variable, both the source and target variable refer to the same array instance in the memory.

The following is an example of copying the array variables:int[] Source = new int[10] {0, 1, 2, 3, 4};

int[] Target= Source;

Initializing and Assigning Values to Array (Contd.)



When an array is initialized, you can access the element values and manipulate them.

The foreach loop is specially used for manipulating arrays.

The following is the syntax of the foreach loop:foreach (type identifier in expression)

{

//statements

}

Manipulating Array Elements



The following is the example of foreach loop:int[] Numbers = { 4, 3, 2, 1, 0, -1, -2, 9, 5 };

Console.WriteLine("The Contents of an Array is:");

foreach (int K in Numbers)

{

Console.WriteLine("{0} \t",K);

}

Manipulating Array Elements (Contd.)



While declaring a method if you are not sure about the number of arguments passed as a parameter, you can use the param array.

The following is the example of param array:public int Adding_ArrayElement(params int[] List)

{

int Total = 0;

foreach ( int I in List )

{

Total += I;

}

return Total;

}

Manipulating Array Elements (Contd.)



Demo: Matrix Subtraction Using Arrays

Problem Statement:David, a student of California University, is currently pursuing mathematics. He is working on a project named Matrix Subtraction. He needs to perform the following tasks for his project:

Accept data in two Arrays.

Perform the subtraction operation.

Verify the value of subtraction.

Help David to create the C# program using Visual Studio IDE.



Solution:To solve the preceding problem, David needs to perform the following tasks:

1. Create a console-based application for Matrix Subtraction.

2. Build and execute an application.

Demo: Matrix Subtraction Using Arrays (Contd.)



Multidimensional Arrays

The rank value of the array is also known as the dimension of the array.

The array can be single dimensional or multidimensional.

Single dimensional array stores data in a row.

Multidimensional array stores data using different dimensions.

The following figure is a graphical representation of values stored in a single dimensional array and a multidimensional array.

int [] Num; int[,] Num; 0

0 1 2 3 4 1

0 1 2 3 4



Multidimensional Arrays (Contd.)

The Array class is the base class for all the arrays in C#.

The Array class provides properties and methods to work with arrays.

Properties: The following table explains some of the most commonly used properties of the Array class.

Properties Explanation

Length Returns the total number of items in all the dimensions of an array

Rank Returns the total number of items in all the dimensions of an array

IsFixedSize Return a value indicating if an array has a fixed size or not

IsReadOnly Returns a value indicating if an array is read-only or not



Multidimensional Arrays (Contd.)

Methods: The following table explains some of the most commonly used methods of the Array class.

Properties Explanation

Sort Performs sort operation on an array passed to it as a parameter

Clear Removes all items of an array and sets a range of items in the array to 0

GetLength Returns the number of items in an Array

GetValue Returns the value of the specified item in an Array

IndexOf Returns the index of the first occurrence of a value in aone-dimensional Array or in a portion of the Array



Using Collections

Arrays are used to collect the elements of same data type.

The .NET Framework provides several classes that also collect elements in specialized ways. Theses classes are the Collection classes, and are declared in the System.Collections namespace and sub-namespaces.



Using Collections (Contd.)

The collection classes accept, hold, and return their elements as items.

The element type of collection class is an object. Object is a reference type.

The following figure shows the storage of values in array of type int:

STACK HEAP

9 7 3 2

Array

@

int [] array= {9, 7, 3, 2};




The action which automatically converts the value type to the reference type, is known as boxing.

The following figure shows the boxing technique.

STACK HEAP

@ @ @ @

Array

@

int [] array= {9, 7, 3, 2};

7 2

39




When you want to access the elements of an array through its index value location in an array, use an ArrayList class.

The following table describes the use of various methods of an ArrayList class.

Method Use

Add Adds an object to the end of the ArrayList

Remove Removes the element at the first occurrence of a specific object from the ArrayList

Clear Removes all the elements from the ArrayList

Insert Inserts an element into the ArrayList at the specified index

TrimToSize Sets the capacity to the actual number of elements in the ArrayList

Sort Sorts the elements in the ArrayList

Reverse Reverses the element in the ArrayList



In this session, you learned that:Memory allocated to variables are of two types, value type and reference type.

Value-types are the simplest types in C#. Variables of value types directly contain their data in the variable.

Reference-types variables contain only a reference to data. The data is stored in a separate memory area.

A value type variable holds its value in the stack.

A reference type variable holds a reference to an object in the heap.

To hold related data of various data type in single variable, structures are used.

C# provides the features of enum to create user defined data types with numbers as an index value to access them.

An array is a collection of values of the same data type.

Summary



The foreach statement interprets the common loop process and removes the need for you to check the array size.

Param arrays are used in the methods with parameter list when the total number of parameters is not known.

The .NET Framework provides several classes that also collect elements together in other specialized ways. These are the Collection classes, and they live in the System namespace.

ArrayList is useful when you want to manipulate the values in an array easily.

Summary (Contd.)

Date post:	17-Jun-2015
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05 iec t1_s1_oo_ps_session_07

Technology