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Access VBA Programming for Beginners - Class 4 -. by Patrick Lasu [email protected] Class 4 - Overview. Coding Concepts Reading Code VB Operators/Characters: Concatenation, Line Continuation, Comments Stepping through Code IF Statements IIF Statements Select Case Statements.

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Access vba programming for beginners class 4

Access VBA Programmingfor Beginners - Class 4 -

by

Patrick Lasu

[email protected]


Class 4 overview
Class 4 - Overview

  • Coding Concepts

    • Reading Code

    • VB Operators/Characters:

      • Concatenation, Line Continuation, Comments

    • Stepping through Code

  • IF Statements

  • IIF Statements

  • Select Case Statements


Coding concepts
Coding Concepts

  • Reading Code

    • Reading code can be tricky

      • Statements to the left and right of an equal sign will not be equal until the code is executed (and then it can be “not equal” again).

    • Tip 1: Read (evaluate) from the right of the equal sign to figure it out

    • Tip 2: Do not worry about “past” statements


Coding concepts1

VBA Code

intValue = 5 + 2

Next Line of Code

Behind the scenes

0 = 5 + 2

Next Line of Code

Coding Concepts

Reading Code – Example 1


Coding concepts2

Behind the scenes

7 = 5 + 2

Next Line of Code

VBA Code

intValue = 5 + 2

Next Line of Code

Coding Concepts

Reading Code – Example 1


Coding concepts3

Behind the scenes

0 = 5

0 = 0 + 2

Next Line of Code

VBA Code

intValue = 5

intValue = intValue + 2

Next Line of Code

Coding Concepts

Reading Code – Example 2


Coding concepts4

Behind the scenes

5 = 5

5 = 5 + 2

Next Line of Code

VBA Code

intValue = 5

intValue = intValue + 2

Next Line of Code

Coding Concepts

Reading Code – Example 2


Coding concepts5

Behind the scenes

7 = 5

7 = 7 + 2

Next Line of Code

VBA Code

intValue = 5

intValue = intValue + 2

Next Line of Code

Coding Concepts

Reading Code – Example 2


Coding concepts6
Coding Concepts

  • Concatenation character:

    & (ampersand)

  • Used for putting expressions together

    Example:

    strFirstName = “John”

    strLastName = “Doe”

    strFullName = strFirstName & “ “ & strLastName

  • Avoid using ‘+’ to concatenate, it can produce unexpected results


Coding concepts7
Coding Concepts

  • Line continuation character:

    _ (underscore)

    Example:

    Msgbox “This is important“, _

    vbOKOnly, “My Message”

    String Example:

    strMsg= “This is a very important “ & _

    “message from me!”

  • Limit is 25 lines, or 24 line continuations


Coding concepts8
Coding Concepts

  • Making comments

    • Use ‘ (apostrophe) to start a comment

    • Comments are not executed; used to document what the code is suppose to do

      • No need to write an essay

        Example:

        ‘Assign a value

        intValue=5

        Rem Example:

        Rem Assign a value

        intValue=5


Coding concepts9
Coding Concepts

  • Stepping through code

    • Use [F5] in the code window to execute the code

    • Use [F8] in the code window to execute the code one step at a time

  • Works in a Standard Module, does not work in a Form Module.


If statement
IF Statement

  • An IF statement evaluates a condition to find out if it is True or False, then executes the appropriate statement(s)

  • Type the word ‘If’ in the code window and press [F1] for help on the topic


If statement1
IF Statement

  • Syntax (Single Line):

    If condition Then [statements] [Else elsestatements]

    If Sales>100K Then Bonus=10% Else Bonus=1%

  • Syntax (Multi-Line)

    If condition Then[statements]

    [Else[elsestatements]]

    End If

Pseudo-code:

If Sales>100K Then

Bonus=10%

Else

Bonus=1%

End If


If statement2
IF Statement

  • Syntax (If…Then…ElseIf…Then…Else)

    If condition Then[statements]

    [ElseIf condition-n Then[elseifstatements] ...

    [Else[elsestatements]]

    End If

If Sales>100K Then

Bonus=10%

ElseIf Sales>50K Then

Bonus=5%

Else

Bonus=1%

End If


If statement3
IF Statement

Pseudo-Code:

If Sales>100K Then

If NewClients>5 Then

Bonus=15%

Else

Bonus=10%

End If

Else

Bonus=1%

End If

  • Nested IF

    If condition Then

    If condition Then

    [statements]

    [Else

    [elsestatements]]

    End If

    [Else

    [elsestatements]]

    End If


If statement4
IF Statement

  • Operators for IF Statement condition

    • Equal (=)

    • Not Equal (<>)

    • Less Than (<)

    • Less Than Or Equal To (<=)

    • Greater Than (>)

    • Greater Than Or Equal To (>=)


If statement5
IF Statement

  • Logical Operators

    • And

    • Or

    • Not

    • Xor

    • Eqv

    • Imp

If Sales>100K And NewClients > 5 Then

If Sales>100K Or NewClients > 10 Then

If Not(Sales>100K) Then


Immediate if
Immediate IF

  • Immediate If is similar to If statements

    • Syntax

      IIf(expr, truepart, falsepart)

      IIf(Sales>100K, Bonus=10%, 1%)

    • Can be nested

      IIf(expr, truepart, IIf(expr, truepart, falsepart))

      IIf(Sales>100K, Bonus=10%, IIf(Sales>50K,Bonus=5%, Bonus=1%))

  • Type the word ‘IIf’ in the code window and press [F1] for help on the topic


Immediate if1
Immediate IF

  • The drawback is that it always evaluates both true and false part

    • It is slower than IF statements

    • Can give unexpected results


Select case
Select Case

  • Select Case is similar to If…Then…ElseIf statements.

  • The difference is that it evaluates an expression once and then compares it to different values

    • Makes it more efficient than multiple ElseIf statements

  • Type the word ‘Select’ in the code window and press [F1] for help on the topic


Select case1
Select Case

  • Syntax:

    Select Case testexpression

    [Case expressionlist1]

    [statements]

    [Case expressionlist2]

    [statements]

    [Case Else]

    [statements]

    End Select

  • Pseudo-Code:

    Select Case Sales

    Case >100K

    Bonus=10%

    Case >50K

    Bonus=5%

    Case Else

    Bonus=1%

    End Select


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