Spring
2013
Bachelor
of Science in Information Technology (BSc IT) – Semester 4
BT0082
– Visual Basic – 4 Credits
(Book
ID: B1093)
Assignment
Set (60 Marks)
1. Explain the method of creating a
new project in VB.Net.
Ans.- Start Microsoft Visual Studio.Net and from
the menu select FileàNewàProject.
A “New Project “ dialog will now be displayed. Select “Visual Basic Project”
from “Project Type” and select “Console Application” from “Templates”. Type
“MyHelloWorldApplicatio( project name)” in the “Name” text box below, then
click OK.
This will show
you the initial default code for your Hello World Application.
Change the
name of module from Module1 to “MyHelloWorldApplication” and type
Console.WriteLine(“Hello World”) inside the Sub Main() function’ body like
whats show below:
Module MyHelloWorldApplication
Sub Main()
Console.WriteLine(“Hello World”)
End Sub
End Module
|
To compile and
execute your application, select “Start” from the “Debug” menu or to run the
application without Debug press Ctrl+F5. A new console window containing the
words “Hello World” will now be displayed. Press any key to terminate the
program and close the console window.
2. Explain Code Editor Window and
Solution Explorer.
Ans.- The
Code Editor Window:- The Code Editor Window, shown in below figure. After
you have designed the user interface for your project by placing controls on
the form, you will turn to the Code Editor to develop the Visual Basic
statements that make the controls functional. The easiest way to call up the
Code Editor is to double-click a control. Then, you can begin typing the Visual
Basic statements that will be executed when the user performs the most common
action on that control. If you double-click on a button, for example, you can
enter the statements that will be executed when the user clicks on that button.
The
Code Editor works much like other text editors you’ve worked with. However, the
Code Editor has a number of special features that simplify the task of editing
Visual Basic code. For example, color is used to distinguish Visual Basic
keywords from variables, comments, and other language elements. And many types
of coding errors are automatically highlighted as you type so you can correct
them. You’ll learn more about working with the Code Editor in the next chapter.
Note that the
Code Editor and the Form Designer provide two different ways to work with the
same Visual Basic source file. The Code Editor lets you work directly with the
Visual Basic statements that make up your application. The Form Designer
presents a visual representation of the forms and controls that are implemented
by that code.
The
Code Editor window is where you create and edit the Visual Basic code that your
application requires. The Code Editor works much like any other text editor you
have used, so you shouldn’t have much trouble learning how to use it. You can
display the Code Editor by double-clicking the form or one of the controls in
the Form Designer window. Or, you can click the View Code button in the
Solution Explorer. Once you’ve opened the Code Editor, you can return to the
Form Designer by clicking the (Design) tab at the top of the Code Editor or the
View Designer button in the Solution Explorer (to the right of the View Code
button). You can also move among these windows by pressing Ctrl+Tab or
Shift+Ctrl+Tab.
It’s
important to realize that the Form Designer and the Code Editor do not
represent two different files. Instead, they provide you with two views of the
same Visual Basic source file. The Form Designer gives you a visual
representation of the form that is implemented by your Visual Basic code. The
Code Editor lets you edit the code for the form.
The Solution Explorer:-
Below figure shows the Solution Explorer, which you use to manage the projects
that make up a solution and the files that make up each project. As you can
see, the files in the Solution Explorer are displayed in a tree view with the
files that make up a project subordinate to the project container and the
project container subordinate to the solution container. If a container has a
plus sign next to it, you can click on the plus sign to display its contents.
Conversely, you can hide the contents of a container by clicking on the minus
sign next to it.
You
can also use the buttons at the top of the Solution Explorer to work with the
files in a project. To display the code for a form, for example, you can
highlight the form file and then click on the View Code button. And to display
the user interface for a form, you can highlight the form file and then click
on the View Designer button. For a code file, only the View Code button is
available since a code file doesn’t contain a user interface.
To
identify the files that make up a project, you can look at the icon that’s
displayed to the left of the file name. The icon for a form file, for example,
is a form, and the icon for a code file is a document and the letters VB. As
you can see, this project consists of three form files and two code files.
Note,
however, that all of the files have the file extension vb regardless of
their contents. Because of that, I recommend that you give your files names
that identify their contents. For example, we add the prefix frm to the
names of our form files. That way, it’s easy to identify the form files
when you work with them outside of the Solution Explorer.
The last four files shown in this figure
are custom files that we developed for this project. In contrast, the first
file (AssmblyInfo) was added automatically when this project was created. This
file receives information whenever the project is compiled into an assembly.
You
use the Solution Explorer to manage and display the files and projects in a
solution. The Solution Explorer lists all of the projects for the current solution,
as well as all of the files that make up each project. Plus (+) and minus (-)
signs in the Solution Explorer indicate groups of files. You can click on these
signs to expand and collapse the groups. You can perform most of the functions
you need using the buttons at the top of the Solution Explorer window. The
buttons you’ll use most are the View Code and View Designer buttons, which open
the Code Editor and Form Designer windows, and the View Properties button,
which opens the Properties window.
3. Write a VB program to short and
display an array of integers in ascending and descending order using the array
concept in VB.Net.
Ans.- Short
an array in Ascending Order
Private Sub
Form_Load()
Dim LngArr(1 To 100) As Long
Dim Var As Variant
Dim i As Long
For i = 1 To 100
LngArr(i) = 100 - i
Next
BubbleSort LngArr
For i = LBound(LngArr) To UBound(LngArr)
Debug.Print i, LngArr(i)
Next
Var = Array(2, 43, 12, 56, 1, 33, 91)
BubbleSort Var
For i = LBound(Var) To UBound(Var)
Debug.Print i, Var(i)
Next
End Sub
Private Sub
BubbleSort(VArr As Variant)
Dim LB As Long, UB As Long
Dim i As Long, j As Long
Dim Tmp As Variant
On Error GoTo ErrSort 'array not dimmed
LB = LBound(VArr) 'lower bound
UB = UBound(VArr) 'upper bound
For i = LB To UB - 1
For j = i + 1 To UB
If VArr(i) > VArr(j) Then
Tmp = VArr(i) 'swap elements
VArr(i) = VArr(j)
VArr(j) = Tmp
End If
Next
Next
Exit Sub
ErrSort:
MsgBox Err.Description
End Sub
Result:- 1, 2, 12, 33, 43, 56, 91
Short an array in Descending Order
Private Sub
Form_Load()
Dim LngArr(100 To 1) As Long
Dim Var As Variant
Dim i As Long
For i = 100 To 1
LngArr(i) = I - 100
Next
BubbleSort LngArr
For i = LBound(LngArr) To UBound(LngArr)
Debug.Print i, LngArr(i)
Next
Var = Array(2, 43, 12, 56, 1, 33, 91)
BubbleSort Var
For i = LBound(Var) To UBound(Var)
Debug.Print i, Var(i)
Next
End Sub
Private Sub
BubbleSort(VArr As Variant)
Dim LB As Long, UB As Long
Dim i As Long, j As Long
Dim Tmp As Variant
On Error GoTo ErrSort 'array not dimmed
LB = LBound(VArr) 'lower bound
UB = UBound(VArr) 'upper bound
For i = LB To UB - 1
For j = i - 1 To UB
If VArr(i) < VArr(j) Then
Tmp = VArr(i) 'swap elements
VArr(i) = VArr(j)
VArr(j) = Tmp
End If
Next
Next
Exit Sub
ErrSort:
MsgBox Err.Description
End Sub
Result:- 91, 56, 43, 33, 12, 2, 1
4. Explain arithmetic and relational
operators in VB.Net.
Ans.- Arithmetic
Operators:- Several common arithmetic operators are allowed in VB.Net given
in the following table
Arithmetic
Operator
|
Meaning
|
+
|
Add
|
-
|
Subtract
|
*
|
Multiply
|
/
|
Divide
|
Mod
|
Remainder of modulo
|
The program below uses three operators
Imports System
Module ArithmeticOperators
‘The program shows the use of arithmetic operators
‘+-*/Mod
Sub Main()
‘result of addition, subtraction, multiplication and modulus operator
Dim sum, difference, product, modulo As Interger
Sum = 0
difference = 0
product = 0
modulo = 0
Dim quotient As Double = 0 ‘result of division
Dim num1 As Interger = 10 ‘operand variables
Dim num2 As Interger = 2
sum = num1+num2
difference = num1-num2
product = num1*num2
quotient = num1/num2
modulo 3 Mod num2
‘remainder of 3/2
Console.WriteLine(“num1 = {0}, sum2 = {1}”, num1, num2)
Console.WriteLine()
Console.WriteLine(“Sum of {0} and {1} is {2}”, num1, num2, sum)
Console.WriteLine(“Difference of {0} and {1} is {2}”, num1, num2,
difference)
Console.WriteLine(“Product of {0} and {1} is {2}”, num1, num2,
product)
Console.WriteLine(“Quotient of {0} and {1} is {2}”, num1, num2,
quotient)
Console.WriteLine()
Console.WriteLine(“Remainder when 3 is divided by {0} is {1}”, num2,
modulo)
End Sub
End Module
|
Relational Operators:-
Relational operators are used to comparison purposes in conditional statements.
The common relational operators in VB.Net are:
Relational
Operator
|
Meaning
|
=
|
Equality check
|
<>
|
Un-equality check
|
>
|
Greater than
|
<
|
Less than
|
<=
|
Less than or equal to
|
>=
|
Greater than or equal to
|
Relational
operators always result in Boolean statement, either True or False. For example
if we have two variables
Dim
num1 = 5, num2 = 6 As Interger
then,
num1
= num2 will result in false
num1<>num2 will result in true
num1>num2 will result in false
num1<num2 will result in true
num1<=num2 will result in true
num1>=num2 will result in false
Only compatible data types can be
compared. It is invalid to compare a Boolean with and Integer, if
Dim
I = 1 As Integer
Dim
b = True As Boolean
thin it is a syntax error to compare i
and b for equality (i=b)
5. Explain If……Then……Else statement
in VB.Nett with an example.
Ans.- Condition checking has always been the most
basic and important construct in any language. VB.Net provides conditional
statements in the form of “If…..Then…...Else” statement. The structure of this
statement is---
If Boolean expression Then
Statement or block of statement
Else
Statement of block of statement
End If
|
Example:-
If i=100 Then
Console.WriteLine(“You reached
hundred”)
Else
Console.WriteLine(“Still you are
not reached hundred”)
End If
|
Only
the first message will be printed in the case of i being 100. In any other case
(when i is not 100), the second message will be printed. You can also use a
block of statements (more than one statement) under any If and Else.
6. Describe the following methods of
the Object class in VB.Net:
a. Equals and ReferenceEquals:-
The Object class supplies two versions of Equals, one shared and one not.
The shared
version has this syntax-----
Overloads Public Shared Function
Equals(Object, Object) As Boolean
and is used in
this form
Equals(a,b)
The non-shared
version has the syntax-----
Overloads
Overridable Public function Equals(Object) As Boolean
and is used in
this form
a.equals(b)
The
two versions of the Equals method are designed to determine whether two items
have the same value, but you should be prepared to overload equals if it makes
sense in your class. Keep in mind that because shared members of classes cannot
be overridden, you can only override the non-shared version of Equals. For example
if you have two ways of representing objects in a value type, you should make
sure that Equals can handle this (This designers did this for the String class
as well, although strictly speaking, this is not a value type.)
The Object class also provides a shared
(not overridable) version of a method called ReferenceEquals. The
ReferenceEquals method determines whether two items refer to the same object;
that is, whether the specified Object instances are the same instance. For
example, two strings, a and b, can have a.equals(b) true and
ReferenceEquals(a,b) false, as this code shows-----
Sub Main()
Dim a As String = “hello”
Dim b As String = “Hello”
Mid(b, 1, 1) = “h”
Console.WriteLine(“is
a.Equals(b)true?” & a.Equals(b))
Console.WriteLine(“is ReferenceEquals(a,b)true?”
& ReferenceEquals(a,b))
Console.WriteLine()
End Sub
|
Is a.Equals(b)true? True
Is ReferenceEqualss(a,b) true? False
|
b. MemberWiseClone:-
The MemberwiseClone method creates a shallow copy by
creating a new object, and then copying the nonstatic fields of the current
object to the new object. If a field is a value type, a bit-by-bit copy of the
field is performed. If a field is a reference type, the reference is copied but
the referred object is not; therefore, the original object and its clone refer
to the same object.
For example,
consider an object called X that references objects A and B. Object B, in turn,
references object C. A shallow copy of X creates new object X2 that also
references objects A and B. In contrast, a deep copy of X creates a new object
X2 that references the new objects A2 and B2, which are copies of A and B. B2,
in turn, references the new object C2, which is a copy of C. The example
illustrates the difference between a shallow and a deep copy operation.
There are
numerous ways to implement a deep copy operation if the shallow copy operation
performed by the MemberwiseClone method
does not meet your needs. These include the following:
·
Call a class constructor of the
object to be copied to create a second object with property values taken from
the first object. This assumes that the values of an object are entirely
defined by its class constructor.
·
Call the MemberwiseClone method to create a shallow copy of an
object, and then assign new objects whose values are the same as the original
object to any properties or fields whose values are reference types. The DeepCopy method in the example illustrates this
approach.
·
Serialize the object to be deep
copied, and then restore the serialized data to a different object variable.
·
Use reflection with recursion to
perform the deep copy operation.
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