1. Introduction to VBA Programming

2. Many Types of Statements
VBA statements
Access object model’s methods and properties
Data Access Object’s methods and properties
ActiveX Data Object

3. Example: To Open a Database
DAO command:
Set db = OpenDatabase("c:\salesdb.mdb")
Access Object Model’s Application Object methods:
CurrentDB method:
Set db = CurrentDB()
OpenCurrentDatabase method:
Set db = OpenCurrentDatabase("c:\salesb.mdb")

4. VB Modules Standard modules:
Standard modules are separated database objects containing one or many procedures. They most often contains utilities functions that are useful in many different circumstances.
Create a standard module:
In the database window, click Modules and New.
Form/Report modules: Containing procedures belong to a form/report
Create a form module:
In the Form Design view, click the Code button

5. Procedures Sub procedures Functions
Private procedures: Can be called only by procedures in the same module.
Public: Can be called by procedures in any module.
Public is the default declaration
Functions
returns a value
Used in an expression
Public/Private

6. To Invoke a Sub Procedure
Use Call statement:
Arguments must be surrounded by parentheses.
Call myProcedure(arg1, arg2, …)
If call is not used, arguments are not surrounded by parentheses.
MyProcedure arg1, arg2, …

7. Variable Declarations
Option Explicit
Dim variableName as DataType
Variable naming rules:
The first character must be a letter.
Use only letters, digits, and underscore.
Cannot contain spaces or periods.
No VB keywords
Naming conventions:
Descriptive
Consistent lower and upper case characters.
Ex. Camel casing: lowerUpper, employeeName

8. VB Data Types Boolean (True/False):
Byte: Holds a whole number from 0 to 255.
Date: date and time, 8 bytes.
Double: real, 8 bytes
Single: real, 4 bytes
Integer: 2 bytes
Long: 4 bytes integer
Currency
String
Object: Holds a reference of an object
Variant

9. Variable Declaration Examples
Dim empName as String
Declare multiple variables with one Dim:
Dim empName, dependentName, empSSN as String
Dim X As Integer, Y As Single
Initiatialization
Dim interestRate as Double

10. Object Reference: Set Declare object variales: Dereferencing objects:
Dim varName As Database
Set db = openCurrentDatabase("c:\salesb.mdb")
Dereferencing objects:
Set varName = Nothing

11. Variable Scope
Procedural-level scope: declared in a procedure with the Dim statement
Module-level: declared in a module’s declaration section (outside any procedure) with either Dim or Private keyword.
Public level scope: a module variable declared with the Public statement.

12. Constants User-defined constants: Built-In constants:
Const NationalDay as date = #7/4/2005#
Built-In constants:
VBA, Access, DAO, ADO

13. Data Conversion
Implicit conversion: When you assign a value of one data type to a variable of another data type, VB attempts to convert the value being assigned to the data type of the variable.
Explicit conversion:
VB.Net Functions: CStr, Ccur, CDbl, Cint, CLng, CSng, Cdate,Val, etc.

14. Date Data Type
Date literals: A date literal may contain the date, the time, or both, and must be enclosed in # symbols:
#1/30/2003#, #1/31/2003 2:10:00 PM#
#6:30 PM#, #18:30:00#

15. Some Date Functions Now: Current date and time Time DateDiff Demo:
Days to Christmas
Dim myDate1, mydate2 As Date
myDate1 = Now
mydate2 = #12/25/2005#
MsgBox (DateDiff("d", myDate1, mydate2))

16. Testing VBA Code with Immediate Window
View/Immediate Window

17. Arithmetic and String Operators
+, -, *, /. \, ^
String Concatenation: &, +
No compound operator:
K=k+1,
not k+=1

18. IF Statement IF condition THEN statements [ELSEIF condition-n THEN
[elseifstatements]
[ELSE
[elsestatements]]]
End If

19. Select Case Structure SELECT CASE testexpression
[CASE expressionlist-n
[Statements]
[CASE ELSE
[elsestatements]
END SELECT

20. Select Case Example SELECT CASE temperature CASE <40
Text1.text=“cold”
CASE < 60
Text1.text=“cool”
CASE 60 to 80
Text1.text=“warm”
CASE ELSE
Text1.text=“Hot”
End Select

21. Loop FOR index – start TO end [STEP step] [statements] [EXIT FOR]
NEXT index
DO [{WHILE| UNTIL} condition]
[EXIT DO]
LOOP

22. Do While/Do Until Private Sub Command1_Click() Dim counter As Integer
Do While counter <= 5
Debug.write(counter)
counter = counter + 1
Loop
Text1.Text = counter
End Sub
Private Sub Command2_Click()
Do Until counter > 5

23. With … End With
Convenient shorthand to execute a series of statements on a single object. Within the block, the reference to the object is implicit and need not be written.
With Text4
.BackColor = vbYellow
.FontSize = 20
.Text = "testtest"
End With

24. . Sub procedure: Procedures Sub SubName(Arguments) … End Sub
To call a sub procedure SUB1
CALL SUB1(Argument1, Argument2, …) Or
SUB1 Argument1, Argument2, …

25. Function Private Function tax(salary) As Double tax = salary * 0.1
End Function

26. Call by Reference Call by Value
The address of the item is passed. Any changes made to the passing variable are made to the variable itself.
ByVal
Default
Only the variable’s value is passed.

27. ByRef, ByVal example Private Sub Command2_Click() Dim myStr As String
myStr = Text0
Call ChangeTextRef(myStr)
Text0 = myStr
End Sub
Private Sub ChangeTextRef(ByRef strInput As String)
strInput = "New Text"

28. MsgBox MsgBox(prompt, other arguments)
MsgBox can return a value representing the user’s choice of buttons displayed by the box.
Use Help to find constants used with the MsgBox

29. InputBox InputBox(Prompt [,Title] [, Default] [, Xpos] [, Ypos])
Xpos is the distance from the left edge of the screen, and Ypos is the distance from the top of the screen. Both are measured in twips (1/1440th of an inch).
Note: The arguments are positional and optional. Enter a comma to skip an argument.
cityName = InputBox("Please enter city name:“, , “SF”)
If cityName = vbNullString Then
MsgBox.Show ("customer click cancel")
Else
Text1 = cityName
End If
Note: vbNullString is a VB keyword representing null value.

30. Modeless form: Other forms can receive input focus while this form remains active.
Modal form: No other form can receive focus while this form remains active.
DoCmd.OpenForm stDocName, , , stLinkCriteria, , acDialog
Note: Macro/OpenForm/Window Mode

31. VBA Functions

32. Monthly Payment Form
Text6 = -Pmt(Text2 / 12, Text4 * 12, Text0)

33. Conditional Required Field
Private Sub Form_BeforeUpdate(Cancel As Integer)
If Year(Now) - Year(Birthdate) < 18 Then
If IsNull(Text14) Then
MsgBox ("You must enter guardian name! ")
Cancel = True
Text14.SetFocus
End If
End Sub

34. Domain Aggregate Functions
Aggregate functions provide statistical information about sets of records (a domain). For example, you can use an aggregate function to count the number of records in a particular set of records or to determine the average of values in a particular field.
The two types of aggregate functions, domain aggregate functions and SQL aggregate functions, provide similar functionality but are used in different situations. The SQL aggregate functions can be included in the syntax of an SQL statement but can't be called directly from Visual Basic. Conversely, the domain aggregate functions can be called directly from Visual Basic code. They can also be included in an SQL statement, but an SQL aggregate function is generally more efficient.

36. Examples From Student form, lookup Fname:
=DLookUp("[fname]","faculty","fid='" & [Forms]![student]![fid] & "'")
From Faculty form, count number of students advised by the faculty:
=DCount("[FID]","Student","FID='" & [Forms]![Faculty]![Fid] & "'")

37. Function Example Function NumberOfStudents(FID)
NumberOfStudents = DCount("sid", "student", "fid='" & Forms!faculty!FID & "'")
End Function

39. AccessObject Object
An AccessObject object refers to a particular Microsoft Access object within the following collections.
AllDataAccessPages
AllDatabaseDiagrams
AllForms
AllFunctions
AllMacros
AllModules AllQueries AllReports AllStoredProcedures AllTables AllViews

40. Collection Structure Methods: Count Item(index), 0-based index Add
Remove

41. For Each … Next Dim formName As String Dim obj As AccessObject
For Each obj In Application.CurrentProject.AllForms
formName = formName + obj.Name + vbCrLf
Next
MsgBox (formName)
MsgBox ("Number of forms: " + CStr(Application.CurrentProject.AllForms.Count))

42. AccessObject Properties
CurrentView Property DateCreated Property DateModified Property FullName Property IsLoaded Property Name Property Properties Property Type Property

43. Is the Faculty form open? If so, in which view?

44. Dim intView As Integer
If CurrentProject.AllForms("faculty").IsLoaded Then
intView = CurrentProject.AllForms("faculty").CurrentView
If intView = 0 Then
MsgBox ("Design view")
ElseIf intView = 1 Then
MsgBox ("Form view")
Else
MsgBox ("Datasheet view")
End If
MsgBox ("Not open")

45. Error Handling

46. Overview
Probably no matter how careful and meticulous you are, some time to time, there will be problems with your code or your application. Some problems will come from you. Some problems will be caused by users. And some problems will be caused by neither you nor your users. This means that there are things you can fix. Those you can avoid as much as possible. And there are situations beyond your control. Still, as much as you can, try anticipating any type of problem you imagine may occur when a user is using your application, and take action as much as possible to avoid bad situations.

47. Error Categories
Syntax: A syntax error comes from your mistyping a word or forming a bad expression in your code.
Run-Time: After all syntax errors have been fixed, the program may be ready for the user. Imagine that, in your code, you indicate that a picture would be loaded and displayed to the user but you forget to ship the picture or the directory of the picture indicated in your code becomes different when a user opens your application.

48. Error Categories
Logic: These are errors that don't fit in any of the above categories. They could be caused by the user misusing your application, a problem with the computer on which the application is running while the same application is working fine in another computer. Because logic errors can be vague, they can also be difficult to fix.

49. Handling Errors
type On Error GoTo followed by the name of the label that would deal with the error.
Ex: Private Sub cmdCalculate_Click()
On Error GoTo cmdCalculate_Click_Error
.....
cmdCalculate_Click_Error:
MsgBox "There was a problem when executing your instructions"
End Sub

50. Handling Errors
Ex. cmdCalculate_Click_Exit: Exit Sub cmdCalculate_ClickError: MsgBox "There was a problem when trying to perform the calculation.", _ vbOKCancel Or vbInformation, _ "Compound Interest" Resume cmdCalculate_Click_Exit End Sub

51. Array

52. Array
You can declare an array to work with a set of values of the same data type. An array is a single variable with many compartments to store values, while a typical variable has only one storage compartment in which it can store only one value. Refer to the array as a whole when you want to refer to all the values it holds, or you can refer to its individual elements.

53. Declare Array
For example, to store daily expenses for each day of the year, you can declare one array variable with 365 elements, rather than declaring 365 variables. Each element in an array contains one value. The following statement declares the array variable with 365 elements. By default, an array is indexed beginning with zero, so the upper bound of the array is 364 rather than 365.
Dim curExpense(0 to 364) As Currency ‘Declaring a Fixed Array
Dim sngArray() As Single ‘Declaring a Dynamic Array

54. Declare Array
ReDim statement is used to change the number of dimensions, to define the number of elements, and to define the upper and lower bounds for each dimension
ReDim Preserve varArray(10)

55. Set value to element of array
To set the value of an individual element, you specify the element's index. The following example assigns an initial value of 20 to each element in the array.
Sub FillArray()
Dim curExpense(364) As Currency
Dim intI As Integer
For intI = 0 to 364
curExpense(intI) = 20
Next
End Sub

56. Changing the Lower Bound
You can use the Option Base statement at the top of a module to change the default index of the first element from 0 to 1. In the following example, the Option Base statement changes the index for the first element, and the Dim statement declares the array variable with 365 elements
Option Base 1
Dim curExpense(365) As Currency Or
Dim curExpense(1 To 365) As Currency
Dim strWeekday(7 To 13) As String

57. Storing Variant Values in Arrays
One way is to declare an array of Variant data type
Dim varData(3) As Variant
varData(0) = "Claudia Bendel"
varData(1) = "4242 Maple Blvd"
varData(2) = 38
varData(3) = Format(" ", "General Date")
The other way is to assign the array returned by the Array function to a Variant variable
Dim varData As Variant
varData = Array("Ron Bendel", "4242 Maple Blvd", 38, _ Format(" ", "General Date"))

58. Multidimensional Arrays
you can declare arrays with up to 60 dimensions
Dim sngMulti(1 To 5, 1 To 10) As Single
Use nested For...Next statements to process multidimensional arrays
Sub FillArrayMulti()
Dim intI As Integer, intJ As Integer
For intI = 1 To 5
For intJ = 1 To 10
sngMulti(intI, intJ) = intI * intJ
Debug.Print sngMulti(intI, intJ)
Next intJ
Next intI
End Sub