database access using ado-i

7/27/2019 Database Access Using ADO-I

1/73

29-Jul-02 Information Technology for

Mana ement

1

Database Access using ADO I(ADO Data Control &

Data Bound Control)

Vivek Gupta

IT & Systems Group

Indian Institute of ManagementLucknow

Doing the best at this moment puts you in the best

place for the next moment

-- Oprah Winfrey


2/73


Mana ement

2

One

ADO Data Control


3/73


Mana ement

3

ADO Data Control The ADO (ActiveX Data Object) data control is the

primary interface between a Visual Basic applicationand a database.

It can be used without writing any code at all! Or, It can be a central part of a complex database

management system.

The ADO data control does not appear in the standardVisual Basic toolbox - it must be added.

Select Project from the main menu, then clickComponents. The Components window will appear.Select Microsoft ADO Data Control, then click OK. Thecontrol will be added to your toolbox.

The data control (or tool) can access databases created byother programs besides Visual Basic (or MS Access).

Some other formats supported include dBase, FoxPro,and Paradox.


4/7329-Jul-02 Information Technology for

Mana ement

4

A form that uses an ADO data control

Description

AnADOdata controldefines the recordsetfor a

form and provides functions for navigating,displaying, adding, and updating records.

Bound controls automatically display the valuesin the fields in the current record of the recordset

thats defined by a data control.


5/73


Mana ement

5

Updating records with a data control

The user can change the data in any one of thebound controls.

Then, when the user clicks on one of the

navigation buttons in the data control to move toanother record, the current record is automatically

updated.

If the user closes the form before moving toanother record, though, the changes are lost.

Deleting records with a data control

Some functions, like deleting records, arent builtinto the data control.

To provide for these functions, you use Visual

Basic code.


6/73


Mana ement

6

TwoData Bound Control

Would be revisiting ADO Data Control soon


7/73


Mana ement

7

Data Bound Controls

Controls that are tied to database fields and

are generally not available for free-forminput.

they automatically display database fields.

(Data aware controls is a synonym.) Data-Bound controls on the form:

Set the bound controls DataSourceproperty

to point to the data control

set the bound controls DataFieldproperty tothe database field it is to display


8/73


Mana ement

8

Data Bound Controls (contd) The DataChanged property is set to True whenever a bound

controls contents are changed by the user. Before ending a program, be sure to check the DataChanged

property of every bound control to see if the user made

changes. As data is displayed in the bound controls, theDataChanged property is set to False.

If the user or any other operation changes the value in thebound control, the DataChanged property is set to True.

Simply moving to another record doesn't affect theDataChanged property.

When the data control starts to move to a different record,the Validate event occurs.

If DataChanged is True for any bound control, the datacontrol automatically invokes the Edit and Update methods topost the changes to the database.

If you don't wish to save changes from a bound control tothe database, you can set the DataChanged property to

False in the Validate event


9/73


Mana ement

9

Data BoundControls Special controls with properties established by

database fields.

A data bound control is needed for each field (column)in the Recordset (database table) we need to view.

Most of the standard Visual Basic tools can be usedas data bound controls

Label: used to provide display-only access to a

specified text data field.Caption property is data bound. Text Box: used to provide read/write access to aspecified text data field. Text property is data bound.

Check Box: Used to provide read/write access to a

Boolean field. Value property is data bound. Picture Box & Image Box: Used to display a graphical

image from a bitmap, icon, gif, jpeg, or metafile file.Provides read/write access to a image/binary data field.Picture property is data bound.


10/73


Mana ement

10

Data BoundControls (contd) Three custom data bound controls,

data bound versions of the standard list box (DataList), thestandard combo box (DataCombo), and the standard grid control(DataGrid).

Properties: To establish the connection of the data bound control to adatabase, we use a few properties:

DataChanged: Indicates whether a value displayed in a boundcontrol has changed.

DataField: Specifies the name of a field in the table pointed to bythe respective data control.

DataSource: Specifies which data control the control is bound to(indirectly specifying the database table).

If the data in any data bound control is changed and the usermoves to another record in the database, the database willautomatically be updated with the new data (assuming it is notReadOnly).

Be aware of this - it is an extremely powerful feature of the

data control, but also a potential source of problems.


11/73


Mana ement

11

Data BoundControls (contd) Steps in placing the controls on a form:

Draw the bound control on the same form as the data

control to which it will be bound.

Set the DataSource property. Click on the drop-down arrowto list the data controls on your form. Choose one.

Set the DataField property. Click on the drop-down arrow to

list the fields associated with the selected data control

records. Make your choice.

Set all other properties, as needed.


12/73


Mana ement

12

An Example


13/73


Mana ement

13

Back to

ADO Data Control


14/73


Mana ement

14

ADO Data Control The data control can perform the following tasks:

Connect to a database.

Open a specified database table.

Create a virtual table based on a database query. Pass database fields to other Visual Basic tools, fordisplay or editing. Such tools are bound to thedatabase, or data bound controls.

Add new records, delete records, or update records. Trap any errors that may occur while accessing data.

Close the database.

As a rule, you need one data control for everydatabase table, or virtual table, you need access to. One row of the table is accessible to each data control

at any one time. This is referred to as the current record


15/73


Mana ement

15

ADO Data Control

When an ADO data control is placed on a form, itappears with the assigned caption and four arrowbuttons:

Move to first/previous/last/next record

The arrows are used to navigate through the tablerecords (rows).

The buttons can be used to move to the beginning ofthe table, the end of the table, or from record torecord.

In most applications, the data control never appearson the form its Visible property is almost alwaysFalse.


16/73


Mana ement

16

ADO Data Control Properties

The ADO data control is connected to a database simplybe setting a few properties. Important properties of thisdata control are:

Align: Determines where data control is displayed. Caption: Phrase displayed on the data control.

CommandType: Establishes source of Recordset (table or query).

ConnectionString: Contains the information used to establish aconnection to a database.

EditMode: Read-only at run-time. Indicates current state of editing for thecurrent record.

LockType: Indicates the type of locks placed on records during editing(default setting makes databases read-only).

Recordset:A set of records defined by a data controls ConnectionStringand RecordSource properties. Run-time only.

RecordSource: Determines the table (or virtual table) the data control isattached to.

Visible: Establishes whether the data control appears on the form at run-

time


17/73


Mana ement

17

More ADO data control properties

Property Des cription

UserName If a user name isnt included in the

ConnectionString property, it must be

specified for this property.Password If a password isnt included in the

ConnectionString property, it must be

specified for this property.

EOFAction Determines what happens when the user

tries to move past the last record in the

recordset.

BOFAction Determines what happens when the user tries to move past the first record in the

recordset.


18/73


Mana ement

18

Some of the data properties of a bound control

Property Des cription

DataSource Identifies the data control that defines the

recordset you want the control bound to.

DataField Identifies the field in the recordset that youwant the control bound to.


19/73


Mana ement

19

ConnectionString Property

After placing a data control on a form, weset the ConnectionStringproperty.

The ADO data control can connect to a

variety of database types. There are three ways to connect to adatabase:

using a data link, using an ODBC data source, or

using a connection string.


20/73


Mana ement

20

Two dialog boxes for building a connection string


21/73


Mana ement

21

ConnectionString Property

Visual Basic can build the connection string for us. The steps to create our example connection string

are: Start a new Visual Basic project and place an ADO Data Control onthe form.

Go to the Properties Window, click on the Connection String. Clickon the ellipsis that appears. The Property Pages window appears.

Choose Use Connection Stringand click the Build button. TheData Link Properties window appears. Choose the Provider tab and select Microsoft Jet 3.51 OLE DB

Provider (an Access database). Click the Next button to go to the Connection tab.

Click the ellipsis and use the Select Access Database dialog box tochoose the BIBLIO.MDB file in your working directory. ClickOpen.

Click Test Connection. Then, click OK (assuming it passed). ClickOK in the Property Pages window. The connection string is builtand assigned to the ConnectionStringproperty of the data control.


22/73


Mana ement

22

ADO Data Control Events

Events that are triggered at various times during databaseaccess, where we write code to perform specific neededtasks. WillMove: Triggers before record pointer is moved from one row to

another.

MoveComplete: Event triggered after record pointer has been moved fromone row to another.

EndofRecordset: Triggers when the record pointer is moved past the lastrecord in the recordset.

WillChangeRecordset: Triggers before a change is made to therecordset. Used to trap unwanted changes.

RecordsetChangeComplete: Triggers after a change is made torecordset.

WillChangeRecord: Triggers before updates for the current row are sentto the data source.

RecordChangeComplete: Triggers after updates for the current row aresent to the data source.

WillChangeField: Triggers before the current field in the recordset isupdated.

FieldChangeComplete: Triggers after the current field in the recordsethas been updated


23/73


Mana ement

23

DAO vs. ADO ?

The primary difference between the two data

controls is in the properties used to connect to a

database.

The DAO control connects to the database using the

DatabaseName property while the ADO control uses

the ConnectionString.

To construct a Recordset, the DAO control uses theRecordSource property. The ADO control requires

setting two properties: RecordSource and

CommandType.

The ADO data control offers more event procedures

than the DAO control to allow more complete control

over database management


24/73


25/73


26/73


Mana ement

26

ADO Recordset Properties

Can only be accessed at run-time. To refer to a Recordset property, use a 'double-dot' notation.

e.g., if you have a data control named datExample, to referto a property named PropertyName, the notation is:

datExample.Recordset.PropertyName

Important data control Recordset properties are: AbsolutePosition: Long integer that either gets or sets the

position of the current record.

BOF: Returns True when the current record is positioned beforeany data.

Bookmark: Sets or returns a bookmark to the current record.Used as a place marker in database management tasks.

EditMode: Indicates the state of editing for the current record. EOF: Returns True when the current record is positioned past any

data.

RecordCount: The total number of records in the Recordset.


27/73


28/73


Mana ement

28

Example: Recordset Navigation

cmdPrevious_Click event:Private Sub cmdPrevious_Click()

datTitles.Recordset.MovePrevious

If datTitles.Recordset.BOF ThendatTitles.Recordset.MoveFirst

End If

End Sub

cmdNext_Click event:Private Sub cmdNext_Click()

datTitles.Recordset.MoveNext

If datTitles.Recordset.EOF Then

datTitles.Recordset.MoveLast

End If

End Sub


29/73


Mana ement

29

Go toADO Data Environment


30/73


Mana ement

30

ThreeADO Object Model


31/73


Mana ement

31

The ActiveX Data Object (ADO) modelConnection

Recordset

Fields Field

Command

Parameters

Errors Error

Parameter


32/73


Mana ement

32

ADO concepts

The Connection object represents a connection toa data source.

A Recordset object represents a set of records

returned from a query. You can use the Fields collection of a Recordset

object to refer to specific fields in the recordset.

A

collection

is simply a set of objects of the sametype.

A Command object contains the definition of acommand, such as a SQL statement, the name of

a table, or the name of a stored procedure.

You can use the Parameters collection of aCommand object to create parameter queries or to

specify arguments for a stored procedure.


33/73


Mana ement

33

ADO concepts (continued)

The Errors collection contains one or more Errorobjects that contain information about the most

recent errors that occurred in response to an ADO

operation.

You can use these objects to get moreinformation than the Visual Basic Err object

provides.

The ADO model lets you access a data sourceusing an object-oriented interface.

That means you can use the same syntax to

access data objects that you use to access objectslike forms and controls.

The ADO model also provides a variety ofproperties, methods, and events for working with

the ActiveX data objects.


34/73


Mana ement

34

How does ADO work ?

ADO is a component for accessing databases

It exposes a few very flexible objects, which exposetheir own properties, methods, and recognize events

The structure of the ADO object model reflects the

operations we perform on a database, We can even guess these objects and their names once

we understand what it takes to access and update a

database. First step to using ADO is to connect to a database

This connection object is our gateway to the database


35/73


Mana ement

35

Common ADO properties

Property ObjectConnectionString Connection

Provider Connection

DefaultDatabase Connection

CursorLocation Connection

Recordset

BOFEOF

Recordset

CursorType Recordset

LockType Recordset

RecordCount Recordset

C ADO th d


36/73


Mana ement

36

Common ADO methods

Method Object

Open Connection

Recordset

AddNew Recordset

Update Recordset

Delete Recordset

MoveFirst

MoveLast

MovePrevious

MoveNext

Recordset

Requery Recordset

Close Connection

Recordset

T i l d l ti f ADO i bl


37/73


Mana ement

37

Typical declarations for ADO variablesDim cnAP As Connection

Dim rsVendors As Recordset

Typical assignment statements for ADOvariablesSet cnAP = New Connection

Set rsVendors = New Recordset

Set rsVendors = Nothing

Typical statements for working withADO variablesrsVendors.Open "Vendors",cnAP,adOpenKeyset, _

adLockOptimistic,adCmdTable

txtName = rsVendors!VendorName

If rsVendors.EOF Then rsVendors.MoveLast

rsVendors.Close

D i i


38/73


Mana ement

38

Description

Use the Dim statement (Private or Public) to declare an objectvariable for an ADO object

After above declaration, we use the Set statement to create

an instance of the object and assign a reference to the

object to the variable. To do this, we use the New keyword and the name of the ADO

object

After creating an instance of an object, we can refer to its

properties, methods, and events in the code.

To disassociate a variable from the object it refers to, assign a

value of Nothing to the value. Then, the system resources

associate with the object are released. To refer to a field in a recordset, code the recordset name, the

bang operator (!), and the field name

as in, rsVendors!VendorName


39/73


Mana ement

39

A procedure that deletes a record from the datasource associated with a data controlPrivate Sub cmdDelete_Click()

If MsgBox("Do you want to delete this record?", _

vbYesNo + vbDefaultButton2 + vbQuestion) _= vbYes Then

adoVendors.Recordset.Delete

adoVendors.Recordset.MoveNext

If adoVendors.Recordset.EOF Then

adoVendors.Recordset.Requery

adoVendors.Recordset.MoveLast

End If

End If

End Sub


40/73


Mana ement

40

Three

UnderstandingCursors & Recordsets

C & R d t


41/73


Mana ement

41

Cursors & Recordsets

There is a direct relationship between SQL Server cursors andVB Recordsets. Every time we issue a SELECT statement, SQL Server

retrieves the qualifying rows and returns them to the caller,

which is a stored procedure or a Visual Basic application. This set of rows is called a cursor When the cursor is passed to the VB application, its stored in a

Recordset object. The cursor contains the info. retrieved from the DB, the raw

information. A Recordset is an ADO object that stores these rows. It contains

the functionality we need to access these rows in the form ofproperties and methods.

A recordset is simply an object that references a cursor. It exposes a number of methods and properties we can use

to navigate the cursor (not the Recordset) and edit the rowsof the underlying cursor.

C & R d


42/73


Mana ement

42

Cursors & Recordsets

A typical application sets up a connection to adatabase and executes commands through thisconnection, but it spends most of its time processing

the rows returned by the DBMS After establishing a connection to the database and

preparing the command object, we can execute thecommand and retrieve the cursor. However, wemust prepare an object where the cursor will bestored. This object is a Recordset variable, that must be

declared as: Dim RS as ADODB.Recordset Then execute the command with theExecute method

and assign the cursor returned to the RS variable: Set RS = Cmd.Execute

f


43/73


Mana ement

43

Types of Cursors Different applications have different requirements,

which get reflected by the cursor-related propertiesas well as by the LockType property

Cursors are categorized according to their type(CursorType property) and where they reside(CursorLocation property)

The type of cursor determines how fresh the cursoris, i.e., whether the application can see changes madeto the cursor by other users or not.

If the cursor resides on the client,then its type is static Other types apply to cursors that reside on server.

C L ti ti


44/73


Mana ement

44

CursorLocation options

Option Des criptionadUseClient The cursor and its associated result set

reside on the client.

adUseServer The cursor and its associated result setreside on the server.

Note

If we use client-side cursors (adUseClient), Visual Basic

automatically sets the cursor type to adOpenStatic withoutnotifying us, no matter what we set the CursorType to.

CursorType options


45/73


Mana ement

45

CursorType options

Option Des criptionadOpenDynamic Opens a dynamic cursor, which includes

changes, additions, and deletions made to

the database by other users.

Uses keys to identify individual records.

Cannot be used to create sorted result sets

from SQL Server data.

adOpenKeyset Opens a keyset cursor, which includeschanges made to the database by other

users.

Additions made by other users arentvisible, but records deleted by other users

are no longer accessible.

Uses keys to identify individual records.


46/73


Mana ement

46

CursorType options (continued)

Option Description

adOpenStatic Opens a static cursor, which doesnt

include changes, additions, and deletions

made to the database by other users.

This is the only type of cursor that can be

created on the client with ADO.

adOpenForwardOnly Opens a forward-only cursor.This cursor is like a static cursor, but you

can only scroll forward through the

records.This type of cursor isnt available when

you define a recordset using a data control.


47/73


Mana ement

47

Three

ADO Saga Continues

LockType options


48/73


Mana ement

48

LockType options

Option Des criptionadLockReadOnly Data can be viewed, but not modified.

When used with SQL Server data, this

causes a shared lock to be placed on the

records so other users can access andchange the data at the same time.

adLockPessimistic Causes the records to be locked

immediately so other users cant change

them.


causes an update lock to be placed on the

records when theyre retrieved. Theupdate lock is upgraded to an exclusive

lock when the records are actually

updated.


49/73


Mana ement

49

LockType options (continued)

adLockOptimistic Causes the records to be locked when

theyre updated.


causes a shared lock to be placed on therecords when theyre retrieved. Then,

when the Update method is issued, the

shared lock is upgraded to an update lock.

And when the records are actuallyupdated, the update lock is upgraded to an

exclusive lock.

adLockBatchOptimistic Used for updating records in batchesinstead of one at a time.

An Unbound form using code to maintain vendor records


50/73


Mana ement

50

An Unbound form using code to maintain vendor records

Description The navigation buttons are an array of command buttons.

When a record is first displayed, the Update button is disabled. As soonas the user makes a change to the data in the form, however, the Update

button is enabled and the Add, Delete, and navigation buttons aredisabled.

To save the changes, the user must click on the Update button or pressthe Enter key to activate the Update button.

Description (continued)


51/73


Mana ement

51

Description (continued)

To cancel the changes, the user can press the Esc key. When the user clicks on the Add button, the controls are

cleared, the Update button is enabled, and the Add,

Delete, and navigation buttons are disabled.

After the data for the new record is entered into theform, the user can save the record by clicking on the

Update button or pressing the Enter key.

To cancel the addition, the user can press the Esc key.

If the user clicks on the Update button to add a newrecord or modify an existing record and a required field

hasnt been entered, a message box is displayed

identifying the field.

When the user presses the Delete key, a dialog box isdisplayed to confirm the delete operation. If the user

confirms the operation, the record is deleted and the

next record in the recordset is displayed.

F ti th t id d th h d


52/73


Mana ement

52

Functions that are provided through code

Function Method orstatement

When executed

Open connection Open method When the form is loaded

Open recordset Open method When the form is loaded

Recordset

navigation

MoveFirst,

MovePrevious,

MoveNext,

MoveLast

When the user clicks on a

navigation button or

when other events require

this movement

Move values

from fields to

controls

Assignment

statements

When the recordset is

opened, when the user

clicks on a navigation

button, when a record isdeleted, and when

changes to a record are

canceled

More functions that are provided through code


53/73


Mana ement

53

More functions that are provided through code

Func tio n Me tho d o rs tate m e nt

Wh e n e x e c u te d

Clear control

values

Assignment

statements

When the user wants to

add a record

Add a newrecord to the

recordset

AddNewmethod

When the user wants toadd a record

Move values

from controls tocurrent record,

and update the

recordset

Assignment

statements,Update method

When the user indicates

that recordset should beupdated with the data for

a new record or the

changes to an old record

Close a

connection or

recordset

Close method W hen the connection or

recordset is no longer

needed


54/73


Mana ement

54

Open method syntax for a Connection objectconnection.Open [ConnectionString][, UserID][, Password]

ConnectionString arguments for SQL Server

Arg ume nt De s c riptio n

Provider The name of the OLE DB provider

(SQLOLEDB)

Server/Data

Source

The name of the server where the database

residesDatabase/

Initial Catalog

The name of the database

UID/UserID The user name to use when connecting to

the data source

PWD/Password The password to use when connecting to the

data source


55/73


Mana ement

55

Statements that open a connection to a SQLServer databaseDim cnAP As Connection

Set cnAP = New Connection

cnAP.CursorLocation = adUseClient

cnAP.Open "Provider=SQLOLEDB;Server=mmaserver;" _

& "Database=AccountsPayable", "ed", "abc4xyz"


56/73


Mana ement

56

Open method syntax for a Recordset objectrecordset.Open [Source][, ActiveConnection][, CursorType][, LockType][, Options]

Argument Des cription

Source A SQL statement, the name of a table, or the name of a stored procedure.

ActiveConnection A valid Connection object or string.

CursorType The type of cursor to be used for therecordset

LockType The type of locking to be used for the

recordset

Options The type of information specified in theSource argument


57/73


Mana ement

57

Statements that open a recordset with a SELECTstatement and a Connection objectDim rsVendors As Recordset, strSQL As String

Set rsVendors = New Recordset

strSQL = "SELECT * FROM Vendors ORDER BY VendorName"

rsVendors.Open strSQL, cnAP, adOpenKeyset, _adLockOptimistic, adCmdText

Statements that open the same recordset using aconnection string and no Connection objectDim strConnection As String

strConnection = "Provider=SQLOLEDB;Server=mmaserver;" _

& "UID=ed;PWD=abc4xyz;Database=AccountsPayable"

rsVendors.Open strSQL, strConnection, adOpenKeyset, _

adLockOptimistic, adCmdText

The properties for two controls in an array


58/73


Mana ement

58

Description

To create a control array, you add two or more controls of

the same type to the form. Then, you change the names of the controls so theyre all the

same and Visual Basic sets the Index property of each

control so its unique.

How to use a control array


59/73


Mana ement

59

To refer to a control in an array, you use the controlname followed by its index number in parentheses,

starting with zero for the first control in the array as in

this example:

cmdNavigate(0)

The controls in a control array are treated as a group. Sowe code a single event procedure for the entire array

When an event occurs on a control in an array, VisualBasic passes an argument to the event procedure that

contains the index of the control that the event occurred

on. Then, you can use that index to determine the

processing thats done.

Code for working with the control array


60/73


Mana ement

60

Code for working with the control array

Private Sub cmdNavigate_Click(Index As Integer)Select Case Index

Case 0

rsVendors.MoveFirst

Case 1

rsVendors.MovePreviousIf rsVendors.BOF Then rsVendors.MoveFirst

Case 2

rsVendors.MoveNext

If rsVendors.EOF Then rsVendors.MoveLast

Case 3

rsVendors.MoveLast

End Select

End Sub

Code for the unbound Vendors form


61/73


Mana ement

61

Code for the unbound Vendors form

Option Explicit 1

Dim mcnAP As Connection

Dim mrsVendors As Recordset

Dim mbAddNew As Boolean

Const msDialogTitle = "Chapter 6 - Vendors (Unbound)"

Private Sub Form_Load() 2

Set mcnAP = New Connection

Set mrsVendors = New Recordset

mcnAP.Open "Provider=SQLOLEDB;Server=mmaserver;" _

& "Database=AccountsPayable", "ed","abc4xyz"

mrsVendors.Open _

"SELECT * FROM Vendors ORDER BY VendorName", _

mcnAP, adOpenKeyset, adLockOptimistic, adCmdText

LoadControlsSetCommandButtons True

SetNavigationButtons True

End Sub


62/73


Mana ement

62

Private Sub LoadControls() 3

With mrsVendors

txtName = !VendorName

txtAddress1 = !VendorAddress1 & ""

txtAddress2 = !VendorAddress2 & ""

txtCity = !VendorCity

txtState = !VendorStatetxtZipCode = !VendorZipCode

txtContact = !VendorContact & ""

txtPhone = !VendorPhone & ""

End With

End Sub

Private Sub SetCommandButtons(bVal As Boolean) 4

cmdAdd.Enabled = bVal

cmdUpdate.Enabled = Not bVal

cmdUpdate.Default = Not bValcmdDelete.Enabled = bVal

End Sub


63/73


Mana ement

63

Private Sub SetNavigationButtons(bVal As Boolean) 5

Dim i As Integer

For i = 0 To 3cmdNavigate(i).Enabled = bVal

Next

End Sub


64/73


Mana ement

64

Private Sub cmdNavigate_Click(Index As Integer) 6With mrsVendors

Select Case Index

Case 0

.MoveFirst

Case 1

.MovePrevious

If .BOF Then .MoveFirst

Case 2

.MoveNext

If .EOF Then .MoveLast

Case 3

.MoveLast

End Select

End With

LoadControls

SetCommandButtons TrueSetNavigationButtons True

txtName.SetFocus

End Sub


65/73


Mana ement

65

Private Sub cmdAdd_Click() 7mbAddNew = True

ClearControls

SetCommandButtons False

txtName.SetFocus

End Sub

Private Sub ClearControls() 8

txtName = ""

txtAddress1 = ""

txtAddress2 = ""txtCity = ""

txtState = ""

txtZipCode = ""

txtContact = ""

txtPhone = ""

End Sub


66/73


Mana ement

66

Private Sub cmdUpdate_Click() 9On Error GoTo ErrorHandler

If ValidData Then

If mbAddNew Then mrsVendors.AddNew

LoadRecord

mrsVendors.UpdatembAddNew = False

SetCommandButtons True


txtName.SetFocus

End If

Exit Sub

ErrorHandler:

DisplayErrorMsg

If mrsVendors.EditMode = adEditAdd Then

mrsVendors.CancelUpdate

End Sub

Private Function ValidData() As Boolean 10


67/73


Mana ement

67

Private Function ValidData() As Boolean 10

Dim strMessage As StringIf txtName = "" Then

txtName.SetFocus

strMessage = "You must enter a vendor name."

ElseIf txtCity = "" Then

txtCity.SetFocus

strMessage = "You must enter a city."

ElseIf txtState = "" Then

txtState.SetFocus

strMessage = "You must enter a state code."

ElseIf txtZipCode = "" Then

txtZipCode.SetFocus

strMessage = "You must enter a zip code."

Else

ValidData = True

End If

If Not ValidData ThenMsgBox strMessage, vbOKOnly, msDialogTitle

End If

End Function


68/73


Mana ement

68

Private Sub LoadRecord() 11

With mrsVendors

!VendorName = txtName

!VendorAddress1 = txtAddress1

!VendorAddress2 = txtAddress2

!VendorCity = txtCity

!VendorState = txtState

!VendorZipCode = txtZipCode

!VendorContact = txtContact

!VendorPhone = txtPhoneEnd With

End Sub

Private Sub cmdDelete_Click() 12

On Error GoTo ErrorHandler


69/73


Mana ement

69

If MsgBox("Do you want to delete this record?", _vbYesNo + vbDefaultButton2 + vbQuestion, _

msDialogTitle) _

= vbYes Then

With mrsVendors

.Delete

.MoveNext

If .EOF Then

.Requery

.MoveLast

End If

LoadControlsEnd With

End If



txtName.SetFocusExit Sub

ErrorHandler:

DisplayErrorMsg

End Sub


70/73


Mana ement

70

Private Sub txtName_Change() 13SetNavigationButtons False


End Sub

Private Sub txtAddress1_Change()SetNavigationButtons False


End Sub

.

.

.

Private Sub txtPhone_Change()

SetNavigationButtons False


End Sub

Private Sub Form_KeyDown(KeyCode As Integer, _ 14

Shift As Integer)


71/73


Mana ement

71

If KeyCode = vbKeyEscape ThenLoadControls



End If

End Sub

Private Sub cmdExit_Click() 15

mrsVendors.Close

mcnAP.Close

Set mrsVendors = Nothing

Set mcnAP = NothingUnload frmVendors

End

End Sub

Private Sub DisplayErrorMsg() 16MsgBox "Error Code: " & Err.Number & vbCrLf & _

"Description: " & Err.Description, _

vbOKOnly + vbCritical, msDialogTitle

End Sub

When bound forms are best

Wh th f l ti l i l


72/73


Mana ement

72

When the forms are relatively simple

When the built-in functions are acceptable to the users

When you need to build an application quickly without fullfunctionality

When unbound forms are best

When the forms are relatively complex

When the user interface needs to work in a way that can't be

accomplished with bound forms When you can't get the bound forms to do what you want them to

do without serious debugging problems (see chapter 7)

Notes You can combine the use of bound and unbound forms.

Unbound forms are commonly used for critical businessapplications.

Character -- the willingness to accept responsibility for one's


73/73


Mana ement

73

own life -- is the source from which self-respect springs.-- Joan Didion

database access using ado-i

Documents