Decision Statements If

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Decision StatementsIf Then and Select Case
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Decision Statements

• The real power of a program comes from the
  ability to change the order of execution using
  control structures.
• There are two statement structures available in
  VB for making decisions.
• The IfThenElse statement is useful when making
  true/false type decisions.
• The Select Case statement is best used for
  multiple-choice type decisions.

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Decision Statements

• The If statement executes a statement when a
  statement condition is true. The statement
  executes another statement when the condition is
  false.
• Syntax If ( condition) Then
• statement(s)
• Else
• statement(s)
• End If

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Flow Chart
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If Statement

• If the sun is shining Then
• go to beach
• Else
• go to class
• End If
• Condition- sun is shining, statement 1- go to
  beach,
• statement 2 - go to class

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Comparison Conditions

• gt greater than
• lt less than
• equal
• ltgt not equal to
• gt greater than or equal to
• lt less than or equal to

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Compound Conditions

• You can use compound conditions to test more than
  one condition. Create compound conditions by
  joining conditions with logical operators, Or,
  And, and Not.
• Ex.
• If optMale.Value True And Val(txtAge.Text) lt21
  Then
• intMinorMaleCount intMinorMaleCount 1
• End If

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Option Buttons and Check Boxes

• Now that you understand If Statements, we can add
  functionality to option buttons and check boxes.
• Option buttons and Check boxes must always be
  created within a frame on the form, otherwise
  they will not work.
• With an If statement we can check the state of
  the button or box and create events based on this
  information.

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Option Buttons and Check Boxes

• For example,
• If chkBlue.Value True Then
• lblName.BackColor vbBlue
• End If
• Or
• If optItalic.Value True Then
• txt.Title.Font.Italic True
• Else
• txtTitle.Font.Italic False
• End If

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Nested If Statements

• If statements that contain additional If
  statements are said to be nested If statements.
• P.130 go over possible forms of nested ifs
• Temp Example, can be either Hot, Moderate or
  Freezing.

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Select Case Statements

• Evaluates a condition at the beginning of the
  statement. The result of this evaluation is
  compared with the values for each Case when a
  match is found the statements associated with it
  are executed.
• For example, lets look at a situation where we
  are interested in an applicants age so that we
  can determine demographics in an area.

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Select Case Statements

• Select Case intApplicantAge
• Casegt17
• blnDrivingAge True
• blnVotingAge True
• Case gt15
• blnDrivingAge True
• blnVotingAge False
• Case Else
• blnDrivingAge False
• blnVotingAge False
• End Select