Microsoft VB 2005: Reloaded, Advanced

1
Microsoft VB 2005 Reloaded, Advanced

• Chapter 2
• Reviewing Microsoft Visual Basic 2005 Reloaded
  Part II

2
Objectives

• Manipulate characters within strings
• Add radio buttons and check boxes to user
  interfaces
• Create Sub procedures and Function procedures
  within applications

3
Objectives (continued)

• Create and manipulate one-dimensional and
  two-dimensional arrays
• Create a structure and manipulate structure
  variables
• Read information from and write information to
  sequential access files

4
String Manipulation and More Controls

• Objective
• Explore ways of examining and manipulating
  strings

5
Determining the Number of Characters Contained in
a String
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Removing Characters from a String
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The Remove Method

• Removes one or more characters located anywhere
  in a string

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The Remove Method (continued)
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Replacing Characters in a String

• The Replace method
• Replaces a sequence of characters in a string
  with another sequence of characters
• The Mid statement
• Replaces a specified number of characters in an
  existing string with characters from another
  string

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Replacing Characters in a String (continued)
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Replacing Characters in a String (continued)
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Inserting Characters in a String

• The PadLeft and PadRight methods
• Both methods pad the string with a character
  until the entire string is a specified length
• The Insert method
• Inserts characters anywhere within a string

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Inserting Characters in a String (continued)
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Inserting Characters in a String (continued)
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Searching a String for Characters

• The StartsWith and EndsWith methods
• Substring
• Contiguous sequence of characters taken from a
  string
• Determines whether a specific substring occurs at
  the beginning or end of a string
• The Contains method
• Determines whether a string contains a specific
  sequence of characters
• The IndexOf method
• Determines where substring might be in a string

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Searching a String for Characters (continued)
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Searching a String for Characters (continued)
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Searching a String for Characters (continued)
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Accessing Characters Contained in a String
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Accessing Characters Contained in a String
(continued)
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Comparing Strings

• The String.Compare method
• Compares strings
• Uses word sort rules when comparing the strings
• Numbers are considered less than lowercase
  letters, which are considered less than uppercase
  letters
• The Like operator
• Allows you to use pattern-matching characters to
  determine whether a string matches a specified
  pattern

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Comparing Strings (continued)
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Comparing Strings (continued)
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Comparing Strings (continued)
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Comparing Strings (continued)
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More Controls

• Using radio buttons
• RadioButton control
• Allows you to limit the user to only one choice
  in a group of two or more choices
• GroupBox controls
• Used so that only one radio button can be
  selected in each group
• Important properties
• Checked
• Name
• Text

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More Controls (continued)
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More Controls (continued)

• Using check boxes
• CheckBox tool
• Allows the user to select any number of choices
  from a group of one or more choices

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More Controls (continued)
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Sub and Function Procedures

• Procedure
• Block of program code that performs a specific
  task
• Function procedure
• Returns a value after performing its assigned
  task
• Sub procedure
• Does not return a value

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Sub Procedures

• Types
• Event procedure
• Procedure associated with a specific object and
  event
• Independent Sub procedure
• Section of code that can be invoked from one or
  more places in an application
• And is independent of any object and event
• Parameter
• Combination of data type and variable name in a
  parameter list
• Stores the information passed to the procedure
  when it is called

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Sub Procedures (continued)
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Sub Procedures (continued)
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Including Parameters in an Independent Sub
Procedure

• Call statement
• Uses the argument list to pass information to a
  procedure when necessary
• The number of arguments listed in the argument
  list must agree with the number of parameters
  listed in the parameter list
• As well as the data type and position of each
  parameter

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Passing Variables to a Sub Procedure

• Passing by value
• Passes only a variables value
• Include the keyword ByVal before the variables
  corresponding parameter
• Passing by reference
• Passes a variables memory address
• Gives the receiving procedure total access to the
  variable
• Include the keyword ByRef before the variables
  corresponding parameter

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Associating a Procedure with Multiple Events

• Event procedure header contains
• Variable sender
• Receives the memory address of the object that
  raised the event
• Variable e
• Contains additional event data provided by the
  object that raised the event
• Handles clause
• Indicates the objects that are associated with
  this event
• Can include several objects and events

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Function Procedures

• Function
• A block of code that performs a specific task and
  returns a value after completing the task
• Visual Basic has many built-in functions
• The Pine Lodge application
• Demonstrates two techniques
• Associating a procedure with multiple events
• Using a Function procedure

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Function Procedures (continued)
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Function Procedures (continued)
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Arrays

• Simple variable (also called scalar variable)
• A variable that is unrelated to any other
  variable
• Array
• Group of related variables

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Using Arrays

• Array
• Group of variables that is given a name
• All variables in the group have the same data
  type
• Most common types of arrays
• One-dimensional arrays
• Two-dimensional arrays

42
One-Dimensional Arrays

• One-dimensional array
• A column (or row) of variables
• Subscript
• Identifies each variable (referred to as an
  element) in a one-dimensional array
• The first element in a one-dimensional array has
  a subscript of 0 (zero)
• Before you can use an array, you first must
  declare (create) it

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One-Dimensional Arrays (continued)
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One-Dimensional Arrays (continued)
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Storing Data in a One-Dimensional Array
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Manipulating One-Dimensional Arrays

• Displaying the contents of a one-dimensional
  array
• You can use a ForNext loop
• The For EachNext statement
• Accesses each element in a group without
  explicitly using the subscripts of the group
  elements
• Calculating the average of one-dimensional
  numeric array elements
• arrayName.Length returns the number of elements
  in arrayName

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Manipulating One-Dimensional Arrays (continued)
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Manipulating One-Dimensional Arrays (continued)

• Determining the highest value stored in a
  one-dimensional array
• Assign the first element of the array as the
  highest
• Compare the highest with the remaining elements
• Updating the highest every time a higher value is
  found
• Sorting the data stored in a one-dimensional
  array
• Array.Sort method sorts the elements in a
  one-dimensional array in ascending order
• Array.Reverse method reverses the array elements

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Parallel One-Dimensional Arrays

• Parallel arrays
• Two or more arrays whose elements are related by
  their positions in the arrays
• Each corresponding element of the separate arrays
  belongs to a single entity

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Two-Dimensional Arrays

• Two-dimensional array
• Can be viewed as a table of values with a fixed
  number of rows and columns
• Storing data in a two-dimensional array
• arrayName(rowSubscript, columnSubscript) value
• Searching a two-dimensional array
• You must iterate through the array using row and
  column subscripts

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Two-Dimensional Arrays (continued)
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Two-Dimensional Arrays (continued)
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Structures and Sequential Access Files

• Structure statement
• Allows you to create your own custom data types
  in Visual Basic
• Custom data types give the programmer more
  control and flexibility in defining and
  describing entities used in a program

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Structures

• Structure (also called a user-defined data type)
• Data type consisting of a group of different
  members
• Structure members
• Can be variables, constants, or procedures
• Variables are referred to as member variables
• Structure statement
• Allows you to create a structure in Visual Basic

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Structures (continued)
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Structures (continued)

• Using a structure to declare a variable
• Structure variables
• Variables declared using a structure
• Syntax
• Dim Private structureVariableName As
  structureName
• To refer to an individual member variable
• structureName.memberVariableName
• Passing a structure variable to a procedure
• Structure variables are passed by value

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Structures (continued)

• Creating an array of structure variables
• Create a new structure
• Declare a one-dimensional array of the type of
  the structure

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File Types

• Input file
• Get information by reading it (reading the
  file)
• Output file
• Send information to it (write to the file)
• Sequential access file
• Accessed in sequence from beginning to end
• Random access file
• Accessed directly without going from beginning to
  end
• Binary access file
• Can be accessed by byte location in the file

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Sequential Access File

• Also referred to as a text file
• It is composed of lines of human-readable text
• Data can be accessed only sequentially

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Writing Information to a Sequential Access File
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Aligning Columns of Information in a Sequential
Access File

• PadLeft and PadRight methods also apply to
  strings written to sequential access files

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Reading Information from a Sequential File
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Determining Whether a File Exists

• An error occurs when the computer attempts to
  read a sequential access file that does not exist
• The FileExists method
• Determines whether the file exists

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The FormClosing Event

• Occurs just before a form is about to be closed
• This happens
• When the computer processes the Me.Close()
  statement in the forms code
• When the user clicks the Close button on the
  forms title bar

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The FormClosing Event (continued)
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The FormClosing Event (continued)
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The Friends Application
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Summary

• Strings Length property
• Determines the number of characters in the string
• Some string methods
• TrimStart, TrimEnd, Trim
• Remove
• Replace
• Mid
• PadLeft, PadRight
• Insert
• StartsWith, EndsWith

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Summary (continued)

• Some string methods
• Contains
• IndexOf
• SubString
• String.Compare
• Like
• Other controls
• Radio buttons
• Check boxes

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Summary (continued)

• Types of procedures
• Sub
• Function
• Call statement invokes an independent Sub
  procedure
• Passing parameters
• By value
• By reference
• Array types
• One-dimensional and two-dimensional