Visual Basic .NET
Fundamentals
Objectives
• Use primitive data types, naming conventions, and style
rules
• Understand and apply the control structures supported in
Visual Basic .NET
• Explain the objects and techniques involved in the
creation of a Multiple Document Interface (MDI)
application
• Understand the purpose and uses of these new
Windows Forms controls: TabControl, ComboBox,
CheckBox, GroupBox, and RadioButton
Using Primitive Data Types, Naming
Conventions, and Style Rules
• Data Types
– Literal
• Has the face value of each occurrence
– Constant
• Is assigned a literal value that does not change
– Variable
• Is a symbolic reference to an address in memory
• Values stored memory block can change during program execution
• Naming Conventions
– Facilitate program readability, understandability, and
maintainability
– Programmer-supplied names must be meaningful
– Variable names are mixed case and consist of a prefix and a
meaningful name
Using Primitive Data Types, Naming
Conventions, and Style Rules (Continued)
• Example variable declarations
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Dim mdecInterestRate As Decimal - A module-level decimal
Public pastructUser - A public array of structures
Static stintLineCtr - A static integer
Dim strMessage - A dynamic local string
• Naming constants
– Const DAYSINWEEK = 7
• Naming functions
– Private Function GetNextRecord()
– Public Sub FindLastName()
– Protected Sub EnableDisableTextboxes(vbln As Boolean)
• Naming classes
– Public Class Student
– Public Class AcademicProgram
• Naming controls
– Controls have a prefix indicating the control’s class
Coding Conventions and Style Rules
• Purpose: to increase code readability, and, therefore, make it easier
to revise and debug
• Using indentation
– To visually identify groups of related statements
• Declaring variables at the lowest level
– If variable needed only inside a procedure, declare it inside that
procedure
– If variable needed only in one form, declare it at form level in that form
– If a variable is needed only inside a standard module, declare it as a
Private variable inside that module
• Using constants
– Use constants rather than numeric values when possible
– Constants improve program readability and also facilitate program
maintenance
• Writing code that is easy to read
– Try to write code that is easy to read, follow, and understand
Control Structures and Structured
Programming
• Control structure
– A method of controlling the execution sequence of instructions at
runtime
• Characteristics of structured programs
– Limited to sequence, selection, and iteration, with unlimited
nesting
– Every procedure has a single entry point and a single exit point
– Using stepwise refinement, programs are broken down logically
or functionally into relatively small blocks of code
– Variables are declared at lowest possible level
– Global variables are used minimally, if at all
• Stub
– A placeholder for a section of code that will be developed later
Visual Basic .NET Control Structures
• Sequence structure
– One statement after another
• Selection structure
– Includes the If statement, Select Case statement, Immediate If
function, and Try statement
• Iteration structures
– Provide for the repeated execution of a statement block
• If statement
– Allows you to specify a condition or test, and if that condition is
met, to then execute one or more imperative statements
Logical Operators
• And
– The result is True only when condition A and conditionB are both True
• Or
– The result is True if at least one of conditionA or conditionB is True
• AndAlso
– The result is True only when conditionA and conditionB are both True
• OrElse
– The result is True if at least one of conditionA or conditionB is True
• Xor
– The result is True only when one and only one of conditionA and
conditionB is True
Truth Table for Visual Basic .NET Logical
Operators
Visual Basic .NET Control Structures
(Continued)
• Select case
– Useful when the evaluation of a single expression can determine
multiple paths
• Immediate If (IIf)
– Examines <condition> and returns <resultA> if the condition is True;
otherwise, it returns <resultB>
– Syntax: <variable> = IIf(<condition>, <resultA>, <resultB>)
• Try … Catch … Finally
– Provides a structured programming solution to the problem of error
trapping
• Do loops
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Principal form of externally controlled loops
Pretest loop
Posttest loop
While test
Until test
For Loop
• Internally controlled loop
• Requires
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Loop control variable (LCV)
Initial value for the LCV
Limit value for the LCV
Step value
Test to determine whether the LCV’s limit value has
been reached (after which the loop is exited)
Using a For Loop for a Sequential Search