Visual Basic .NET Fundamentals

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Visual Basic .NET Fundamentals
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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

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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

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Using Primitive Data Types, Naming Conventions,
and Style Rules (Continued)

• Example variable declarations
• 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 controls
  class

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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

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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

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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

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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

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Truth Table for Visual Basic .NET Logical
Operators
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Visual Basic .NET Control Structures (Continued)

• Select case
• Useful when the evaluation of a single expression
  can determine multiple paths
• Immediate If (IIf)
• Examines ltconditiongt and returns ltresultAgt if the
  condition is True otherwise, it returns
  ltresultBgt
• Syntax ltvariablegt IIf(ltconditiongt, ltresultAgt,
  ltresultBgt)
• Try Catch Finally
• Provides a structured programming solution to the
  problem of error trapping
• Do loops
• Principal form of externally controlled loops
• Pretest loop
• Posttest loop
• While test
• Until test

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For Loop

• Internally controlled loop
• Requires
• Loop control variable (LCV)
• Initial value for the LCV
• Limit value for the LCV
• Step value
• Test to determine whether the LCVs limit value
  has been reached (after which the loop is exited)

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Using a For Loop for a Sequential Search