leccion 7 - usando ado

8/3/2019 leccion 7 - usando ado

1/59

[VISUAL BASIC CON BASE DE DATOS] IDSYSTEMS 2012

Leccion 7 Usando ADO Pgina 1

This tutorial describes how you can use ADO objects in VB6. Now days, almost any time you write full

fledged database application you will want to use ADO. Along with this, as your applications become

more and more complex you will probably not want to rely on Visual Basic's data controls, but insteaduse the ADO objects directly. Read on to find out exactly how this can be done.

Originally Written By TheVBProgramer.

The "Alphabet Soup" of Database Access

Prior to VB6 and the introduction of ADO (ActiveX Data Objects), VB programmers would generally use DAO(Data Access Objects) to interact with local databases such as MS Access and use RDO (Remote Data Objects)to interact with client/server databases such as Oracle and SQL Server. The concept behind Visual Basic ADOwas Universal Data Access (UDA), where one database access method could be used for any data source; it wasdesigned to replace both DAO and RDO. DAO remains a viable technology for interacting with MS Accessdatabases as it is faster than ADO for that purpose; however, ADO is more flexible using ADO, one coulddevelop a prototype database application using MS Access in the back-end, and with a "flick of the wrist" (i.e.,

with very little coding changes) "upsize" that same application to use Oracle or SQL Server. As far as RDO isconcerned, no new versions of it have been developed beyond the version that shipped with Visual Basic, andthere are no future plans for it.

In the VB4 and VB5 worlds, RDO was the main method used to interact with client/server databases. RDO worksperfectly fine with VB6, so when folks migrated their VB5 applications over to VB6, little or no coding changeswere required. However, ADO is the preferred method of database access for new VB6 applications .

About this Tutorial

This tutorial presents three small sample applications using ADO. All three applications use a local MS Accessdatabase.

The first sample application introduces the ADO Data Control (ADODC) which demonstrates a "quick and dirty"way to connect to a remote database. The second and third applications use ADO code: the second allowsnavigation and searching of a database table; the third allows navigation and updating on a database table. Allthree connect to an ODBC Data Source, which must be set up through the Windows Control Panel. How to dothis is described below.

Note: If you have previously set up a DSN for the Biblio database as described in the previous topic on RDO, youcan skip the section on setting up an ODBC data source and resume here.

Setting Up an ODBC Data Source

Follow the steps below to set up an ODBC Data Source (this process is also called "setting up a DSN", where"DSN" stands for "Data Source Name"). These steps assume Windows 2000 for the operating system. On otherversions of Windows, some steps may vary slightly.

Via Windows Control Panel, double-click on Administrative Tools, then Data Sources (ODBC). TheODBC Data Source Administrator screen is displayed, as shown below. Click on the System DSN tab.


2/59



Click the Add button. The Create New Data Source dialog box will appear. Select Microsoft Access Driver(*.mdb) from the list and click the Finish button.


3/59



The ODBC Microsoft Access Setup dialog box will appear. For Data Source Name, type Biblio. If desired,you can type an entry for Description, but this is not required.

Click the Select button. The Select Database dialog box appears. On a default installation of VB6 or VisualStudio 6, the BIBLIO.MDB sample database should reside in the folder C:\Program Files\Microsoft VisualStudio\VB98. Navigate to that folder, select BIBLIO.MDB from the file list, and click OK.

Note: If VB was installed in a different location on your system, navigate to the appropriate folder. If you do nothave the BIBLIO.MDB sample database file on your system at all, you can download it here. In that case, copy

the file to the folder of your choice, and navigate to that folder to select the database for this step.

When you are returned to the ODBC Microsoft Access Setup screen, the database you selected should bereflected as shown below. Click OK to dismiss this screen.


4/59


5/59



Sample Application 1: Using the ADO Data Control (ADODC)

To build the first sample application, follow the steps below.

Start a new VB project, and from the Components dialog box (invoked from the Project -> Componentsmenu), select Microsoft ADO Data Control 6.0 (SPx) as shown below and click OK.

The ADO Data Control should appear in your toolbox as shown below:


6/59



Put an ADO Data Control on your form, and set the properties as follows:

Property ValueName adoBiblio

DataSourceName BiblioSQL select * from authors

Now put three text boxes on the form, and set their Name, DataSource, and DataField properties as follows:

Name DataSource DataFieldtxtAuthor adoBiblio AuthortxtAuID adoBiblio Au_IDtxtYearBorn adoBiblio Year Born

Save and run the program. Notice how it works just like the other data control.

Now change the SQL property of the data control to select * from authors order by author and run theprogram again. Notice the difference.

Change the SQL property back to what it was and add three command buttons to the form, and set theirName and Caption properties as follows:


7/59


8/59



Download the project files for this sample application here.

Sample Applications 2 and 3: Using ADO Code

Note: If you have previously downloaded and set up a DSN for the Property database as described in theprevious topic on RDO, you can skip the set up steps below and resume here.

Sample applications 2 and 3 use a database called PROPERTY.MDB and can be downloaded here.

The Property database contains just one table called "Property". The columns of this table are defined as follows:

Column Name Data Type NotesPROPNO Number (Long Integer) A number that uniquely identifies the property in the

table. Should be treated as the Primary Key(although it is not defined as such in the sampledatabase).

EMPNO Number (Long Integer) A number that identifies the real estate agent sellingthe property. In a real system, this would be theforeign key to the employee number in an Employeetable (such a table is not present in the sample

database).ADDRESS Text (20) The street address of the property.CITY Text (15) The city where the property is located.STATE Text (2) The state where the property is located (2-character

US state abbreviation).ZIP Text (5) The zip code where the property is located.NEIGHBORHOOD Text (15) The descriptive name of the neighborhood in which

the property is located.HOME_AGE Number (Long Integer) Age in years of the home. (A better table design


9/59



choice would be to have this field be the date inwhich the property was built and have the applicationcompute the age based on the current date.)

BEDS Number (Long Integer) Number of bedrooms in the property.BATHS Number (Single) Number of bathrooms in the property (allows for a

decimal value such as 2.5, indicating 2 bathrooms

i.e. 2 full bathrooms and 1 "powder room").FOOTAGE Number (Long Integer) The footage of the property.ASKING Number (Long Integer) Asking price of the property in whole dollars.BID Number (Long Integer) Bid amount of the potential buyer in whole dollars.SALEPRICE Number (Long Integer) Sale price (amount the property actually sold for) in

whole dollars.

Before coding or running sample application 2 or 3, you must set up an ODBC data source as was done for theprevious sample application.

After downloading the file, move it to the folder of your choice. Then follow the exact same steps as before to setup the DSN, with these two exceptions:

(1) On the ODBC Microsoft Access Setup dialog box, type PropDB for the Data Source Name.

(2) In the Select Database dialog box, navigate to the location where you have placed the PROPERTY.MDB file.

Sample Application 2

To build Sample Application 2, start a new VB project and perform the following steps.

From the Project -> References menu, check Microsoft ActiveX Data Objects 2.x(where x is the highestversion that you have on your system) and click OK.


10/59



This project uses the StatusBar control, so include the Microsoft Windows Common Controls 6.0(SP6)from the Components dialog box, accessed from the Project -> Components menu.


11/59



Create the form shown below. The names of the text boxes in the top frame are shown in the form. Set theEnabled property of the frame to False, which will automatically disable all of the textboxes within it, which isdesired because this application does not allow updating of the data. The settings for the other controls are givenbelow.

The navigation buttons have the following properties:

Name CaptioncmdMoveFirst

The text box in the middle of the form has the following properties:

Name txtCurrentQueryMultiLine TrueLocked True


12/59



The command buttons have the following properties:

Name Caption EnabledcmdAllData Reload All Records TruecmdGetData Run Query Now False

In the "Select Criteria" frame:

The check boxes are an array:

Name CaptionchkCriteria(0) EmpNochkCriteria(1) CitychkCriteria(2) State

The labels are also an array:

Name Caption EnabledlblCriteria(0) = FalselblCriteria(1) Like FalselblCriteria(2) Like False

The textboxes are also an array:

Name Caption EnabledtxtCriteria(0) EmpNo FalsetxtCriteria(1) City FalsetxtCriteria(2) State False

Place the StatusBar on the form and set its Style property to 1 sbrSimple.

2. Code the General Declarations section as shown below. Here, two ADO objects, ADODB.Connection andADODB.Recordset, are defined at the form level.

The ADODB.Connection object represents an open connection to a data source and a specific database on thatdata source, or an allocated but as yet unconnected object, which can be used to subsequently establisha connection.

The ADODB.Recordset object represents the rows that result from running a query,


13/59



Option Explicit

Dim mobjADOConn As ADODB.Connection

Dim mobjADORst As ADODB.Recordset

Dim mstrSQL As String

3. Code the Form_Load event. Here, the connection object variable mobjADOConn is made available for use bysetting it to a new instance of ADODB.Connection. Then, the ConnectionString property and the Openmethod of the ADODB.Connection object are used.

The ConnectionString property takes a string with various arguments delimited by semicolons. When using a DSNas we are in this sample application, you typically need just the DSN name, the user id, and thepassword. The Open method then opens the connection to the database.

'-----------------------------------------------------------------------------

Private Sub Form_Load()

'-----------------------------------------------------------------------------

'set up the form and connect to the data source

On Error GoTo LocalError

'center the form:

Me.Top = (Screen.Height - Me.Height) / 2

Me.Left = (Screen.Width - Me.Width) / 2

' Connect to the Property database:

Set mobjADOConn = New ADODB.Connection

mobjADOConn.ConnectionString = "DSN=PropDB;Uid=admin;Pwd=;"

mobjADOConn.Open

Call cmdAllData_Click


14/59



Exit Sub

LocalError:

MsgBox Err.Number & " - " & Err.Description

End Sub

4. Code the cmdAllData_Click event, which sets or resets the ADODB.Recordset object with a query to display allthe rows in the table. The opening of the recordset takes place in the OpenNewRecordset subprocedure,called from this event procedure.

'-----------------------------------------------------------------------------

Private Sub cmdAllData_Click()

'-----------------------------------------------------------------------------


Dim lngX As Long

'select or reload the data to be displayed:

mstrSQL = "select * from property"

Call OpenNewRecordset

'load data into the text boxes

Call DataLoad

' reset the state of the search criteria controls

For lngX = 0 To 2

chkCriteria(lngX).Value = vbUnchecked

Next

Exit Sub


15/59



LocalError:


End Sub

5. Create the user-defined subprocedure OpenNewRecordset.

Here, the recordset object mobjADORst is made available for use by setting (or resetting) it to a new instance ofADODB.Recordset.

The CursorLocation property is then set to the built-in constant adUseClient. The term "cursor" refers to thetemporary rows of a recordset. The cursor location determines whether the cursor is stored on the clientor the server, specified by the values adUseClient and adUseServer, respectively. Server-side cursor

(adUseServer) is the default. There are tradeoffs using both types of cursors. Client-side cursors can takea long time to build because the data must be pulled over to the client, but once built, traversing thecursor is usually very fast. Client-side cursors often support more features than server-side cursors (thereason this sample application is using a client-side cursor is because we want to use AbsolutePositionproperty later, which only works with a client-side cursor). On the other hand, server-side cursors usuallybuild faster but often support fewer features that client-side cursors.

The Open method of the recordset is then executed. The Open method has the following syntax:

RecordsetObject.Open Source, ActiveConnection, CursorType, LockType, Options

The Sourceargument is an optional variant that evaluates to a valid Command object, SQL statement, tablename, stored procedure call, or filename of a persisted recordset.

The ActiveConnectionargument is an optional variant that evaluates to a valid Connection object variable nameor a string containing connection string parameters.

The CursorTypeargument is an optional value that determines the type of cursor that the provider should usewhen opening the recordset. The possible values and their descriptions are given below:

Value Description

adOpenForwardOnly (default) Used to open a forward-only cursor. Forward-only cursors create staticsnapshots of data. A recordset that uses a forward-only cursor is not directlyupdateable and can only be scrolled from beginning to end (i.e., "MoveNext" isthe only "Move" method that can be used with this type of cursor). Forward-onlycursors offer optimal performance in exchange for feature limitations. Forward-only cursors are sometimes referred to as firehosecursors.

adOpenStatic Used to open a static cursor. A static cursor is a static copy of the data in thedata source. Once created, no changes made by other users propagate to therecordset; the recordset never changes. Note: Client side cursors (like the one


16/59



used in this sample application) use only adOpenStatic for CursorTypesregardless of which CursorType you select.

adOpenDynamic Used to open a dynamic cursor. A dynamic cursor is a "live" recordset, meaningthat any and all additions, changes, and deletions by other users affect therecordset. Dynamic-cursor recordsets support all types of navigation, includingbookmarks (if bookmarks are supported by the provider). Dynamic cursors offer

the most features of any cursor type, but at the expense of increased overhead.adOpenKeyset Used to open a keyset cursor. Keyset cursors are like dynamic cursors, exceptadditions made by other users are not visible in the recordset. The recordset isaffected by changes and deletions, however.

The LockTypeargument is an optional value that determines the type of locking that the provider should usewhen opening the recordset. The possible values and their descriptions are given below:

Value DescriptionadLockReadOnly (default) Specifies read-only locking. Records can be read, but data cannot be

added, changed, or deleted. This is the locking method used with static cursors

and forward-only cursors.adLockPessimistic Specifies pessimistic locking. The provider does what is necessary to ensure

successful editing of records, usually by locking records at the data sourceimmediately upon editing.

adLockOptimistic Specifies optimistic locking. The provider locks records only when you call theUpdate method, not when you start editing.

adLockBatchOptimistic Specifies optimistic batch locking. Records are locked in batch update mode,as opposed to immediate update mode. This option is required for client-sidecursors.

The Optionsargument is an optional Long value that indicates how the Source should be evaluated. The possiblevalues and their descriptions are given below:

Value DescriptionadCmdText Indicates that the provider should evaluate CommandText as a textual definition

of a command. This options is used SQL statements.adCmdTable Indicates that the provider should evaluate CommandText as a table. adCmdStoredProc Indicates that the provider should evaluate CommandText as a stored

procedure.adCmdUnknown Indicates that the type of command in the CommandText argument is not

known and that the provider should attempt to interpret it. Typically results inpoor performance.

adExecuteAsync Indicates that the command should execute asynchronously.adFetchAsync Indicates that the remaining rows after the initial quantity specified in the

CacheSize property should be fetched asynchronously.

'-----------------------------------------------------------------------------

Private Sub OpenNewRecordset()

'-----------------------------------------------------------------------------


17/59



Set mobjADORst = New ADODB.Recordset

mobjADORst.CursorLocation = adUseClient

mobjADORst.Open mstrSQL, mobjADOConn, adOpenStatic, , adCmdText

' display current query

txtCurrentQuery.Text = mstrSQL

End Sub

6. Create the user-defined subprocedure DataLoad. This subprocedure gets the data from the recordset and putseach field into a text box. Data from the recordset is accessed via the Fields collection.

The Fields collection in ADO works identically to the Fields collection in DAO. A field can be referenced with orwithout specifying Fields, either by the field name in quotes or by its ordinal position in the resultset. Thefield can also be referenced with the bang (!) operator. All of the following would be valid ways ofreferencing the field "propno":

mobjADORst.Fields("propno")

mobjADORst ("propno")

mobjADORst.Fields(0)

mobjADORst(0)

mobjADORst!propno

'-----------------------------------------------------------------------------

Private Sub DataLoad()

'-----------------------------------------------------------------------------


'copy the data from the recordset to the text boxes:

txtPropNo.Text = mobjADORst.Fields("propno")

txtEmpNo.Text = mobjADORst.Fields("empno")


18/59



txtAddress.Text = mobjADORst.Fields("address")

txtCity.Text = mobjADORst.Fields("city")

txtState.Text = mobjADORst.Fields("state")

txtZip.Text = mobjADORst.Fields("zip")

Call SetRecNum

Exit Sub

LocalError:


End Sub

7. Create the user-defined subprocedure SetRecNum. This sub displays the number of the current record at thebottom of the screen. The AbsolutePosition and RecordCount properties of the Recordset are usedhere.

The AbsolutePosition property specifies the current row in a recordset. Note: For AbsolutePosition to return avalid value with Access (Jet) databases (like the one used in the sample application), the CursorLocationmust be set to adUseClient. An invalid value (-1) will be returned if adUseClient is specified.

The RecordCount property the total number of rows in the recordset. Note: RecordCount will not return a validvalue with all cursor types (for example, RecordCount will return -1 with a forward-only cursor.) To ensurea valid RecordCount value, use either adOpenKeyset or adOpenStatic as the CursorType for server sidecursors or use a client side cursor.

'-----------------------------------------------------------------------------

Private Sub SetRecNum()

'-----------------------------------------------------------------------------

StatusBar1.SimpleText = "row " & mobjADORst.AbsolutePosition _

& " of " & mobjADORst.RecordCount

End Sub

8. Code the events for the navigation buttons as shown below, using the recordset "Move" methods to move tothe first, last, next, or previous record, respectively.

'-----------------------------------------------------------------------------


19/59



Private Sub cmdMoveFirst_Click()

'-----------------------------------------------------------------------------


mobjADORst.MoveFirst

Call DataLoad

Exit Sub

LocalError:


End Sub

'-----------------------------------------------------------------------------

Private Sub cmdMoveLast_Click()

'-----------------------------------------------------------------------------


mobjADORst.MoveLast

Call DataLoad

Exit Sub

LocalError:


End Sub

'-----------------------------------------------------------------------------

Private Sub cmdMoveNext_Click()

'-----------------------------------------------------------------------------


20/59


21/59




End Sub

9. When one of the check boxes is clicked, the label and text box next to it should be enabled (or disabled, ifclicking the check box unchecks it). Note also that the cmdGetData button (the one with the "Run QueryNow" caption) should only be enabled if one of the checkboxes is checked.

'-----------------------------------------------------------------------------

Private Sub chkCriteria_Click(Index As Integer)

'-----------------------------------------------------------------------------

' disable the 'Run Query Now' button

cmdGetData.Enabled = False

'when the user clicks on a check box, enable the label and text

'box that go with it.

If chkCriteria(Index).Value = vbChecked Then

txtCriteria(Index).Enabled = True

lblCriteria(Index).Enabled = True

txtCriteria(Index).SetFocus

txtCriteria(Index).SelStart = 0

txtCriteria(Index).SelLength = Len(txtCriteria(Index).Text)

' enable the 'Run Query Now' button only if a box is checked.

cmdGetData.Enabled = True

Else

txtCriteria(Index).Enabled = False

lblCriteria(Index).Enabled = False

End If

End Sub


22/59



10. After the user has selected which fields to use and entered values in the text boxes, they click thecmdGetData button to create a new recordset with new data. Note that if the user selects (checks) a field,but does not enter search criteria in the corresponding textbox, an error message is generated and thequery is not run.

'-----------------------------------------------------------------------------

Private Sub cmdGetData_Click()

'-----------------------------------------------------------------------------

'run the query that the user has created


Dim blnFirstOne As Boolean

blnFirstOne = True

mstrSQL = "select * from property where "

If chkCriteria(0).Value = vbChecked Then

If (txtCriteria(0).Text = "") Or (Not IsNumeric(txtCriteria(0).Text)) Then

MsgBox "Employee number is missing or non-numeric. Query not run.", _

vbExclamation, _

"ADO Example"

Exit Sub

End If

blnFirstOne = False

mstrSQL = mstrSQL & "empno = " & txtCriteria(0).Text

End If


If txtCriteria(1).Text = "" Then


23/59



MsgBox "City criteria is missing. Query not run.", _

vbExclamation, _

"ADO Example"

Exit Sub

End If

If blnFirstOne = False Then

mstrSQL = mstrSQL & " and"

End If

blnFirstOne = False

mstrSQL = mstrSQL & " city like '" & txtCriteria(1).Text & "'"

End If


If txtCriteria(2).Text = "" Then

MsgBox "State criteria is missing. Query not run.", _

vbExclamation, _

"ADO Example"

Exit Sub

End If

If blnFirstOne = False Then

mstrSQL = mstrSQL & " and"

End If

blnFirstOne = False

mstrSQL = mstrSQL & " state like '" & txtCriteria(2).Text & "'"

End If

OpenNewRecordset

'make sure that the query did not return 0 rows:


24/59



If mobjADORst.EOF Then

MsgBox "Your query (" & mstrSQL & ") returned no records! " _

& "The default query to return all records will now be rerun.", _

vbExclamation, _

"ADO Example"

'reload the form with all the records

cmdAllData_Click

Else

MsgBox "Your query returned " & mobjADORst.RecordCount & " records.", _

vbInformation, _

"ADO Example"


Call DataLoad

End If

Exit Sub

LocalError:


End Sub

11. Save and run. Note: When entering the "Like" criteria for City and/or State, you can use the wildcard character% to represent any number of characters and the wildcard character _ (underscore) the represent asingle character. For example, entering "M%" for the City criteria would return all rows where the city fieldbegins with the letter "M".


Sample Application 3


25/59



Sample Application 3 demonstrates how to add, update, and delete records with ADO.

When the application is first run, the user is prompted to enter a minimum asking price to possibly limit thenumber of records they want to work with (i.e., "I only want to work with properties that are selling for $200,000 ormore). If the user wants to work with all properties, they would simply accept the default of 0 from the prompt. Ifthe user clicks the Cancel button, the application will end.

Once the user has entered the minimum asking price, the main screen of the application is displayed. Initially, thescreen is in "browse" mode, where the user can use the navigation buttons to move to the first, previous, next orlast record. The data cannot be edited in this mode. If they want to initiate an add or an update, delete a record, orexit the application, they may do so via the appropriate button. Saving or cancelling is not applicable in this mode,so those buttons are disabled.

If the user clicks the Add button, the fields on the screen are enabled and cleared, and the user can enter theinformation for the new property. All buttons except Save and Cancel are now disabled. After the user has madeentries in the fields, he or she would click Save to add the new record to the database table, or, if they changedtheir mind, would click Cancel to discard the new record. In either case (clicking Save or Cancel) the user isreturned to browse mode. When Save is clicked, the application validates the entries and will only save the recordif all fields pass edit (otherwise, a message will appear indicating the problem entry and focus will be set to theproblem field).


26/59



If the user clicks the Update button, the fields on the screen are enabled and the user can modify any or all of thefields (except for the Property Number, which is the primary key of the table). All buttons except Save and Cancelare now disabled. After the user has made modifications in the desired fields, he or she would click Save toupdate the record to the database table, or, if they changed their mind, would click Cancel to discard the changes.In either case (clicking Save or Cancel) the user is returned to browse mode. When Save is clicked, theapplication validates the entries and will only save the record if all fields pass edit (otherwise, a message willappear indicating the problem entry and focus will be set to the problem field).


27/59


28/59



This project uses the StatusBar control, so include the Microsoft Windows Common Controls 6.0(SP6)from the Components dialog box, accessed from the Project -> Components menu. Check this item andclick OK.


29/59



Create the form shown below. The settings for the various controls are given below.


30/59



There are nine textboxes in the main frame of the form. The names and MaxLength settings for these aregiven below:

Name PropertiestxtPropNo MaxLength: 5txtEmpNo MaxLength: 4

txtAddress MaxLength: 20txtCity MaxLength: 15txtState MaxLength: 2txtZip MaxLength: 5txtBeds MaxLength: 1txtBaths MaxLength: 3 (allows fractional amount, like 1.5)txtAsking MaxLength: 0 (not specified)

Set up the Command Buttons as follows:

Name CaptioncmdMoveFirst cmdAdd AddcmdUpdate UpdatecmdDelete DeletecmdSave SavecmdCancel CancelcmdExit Exit

All controls on your form should have their TabIndex property set such that the tabbing order is correct.

Add a Module to the project, name it modCommon, and enter the code shown below. The code containsprocedures described as follows:

CenterForm Sub to center a form on the screenValidKey Function to validate a keystroke for use in the KeyPress event of a textbox ConvertUpper Function to convert an alphabetic character entered in a textbox to uppercase,

used in the KeyPress event of a textboxSelectTextBoxText Sub to highlight the text of a textbox when it receives focus. Used in the

GotFocus event of a textbox.TabToNextTextBox Sub to "autotab" from one textbox to another when maximum number of

characters that can be entered into the first textbox has been reached.UnFormatNumber Function to strip out non-numeric characters (dollar signs, commas, etc.) from a

formatted number.

Option Explicit


31/59



Public Const gstrNUMERIC_DIGITS As String = "0123456789"

Public Const gstrUPPER_ALPHA_PLUS As String = "ABCDEFGHIJKLMNOPQRSTUVWXYZ,'-"

Public gblnPopulating As Boolean

'------------------------------------------------------------------------

Public Sub CenterForm(pobjForm As Form)

'------------------------------------------------------------------------

With pobjForm

.Top = (Screen.Height - .Height) / 2

.Left = (Screen.Width - .Width) / 2

End With

End Sub

'------------------------------------------------------------------------

Public Function ValidKey(pintKeyValue As Integer, _

pstrSearchString As String) As Integer

'------------------------------------------------------------------------

' Common function to filter out keyboard characters passed to this

' function from KeyPress events.

'

' Typical call:

' KeyAscii = ValidKey(KeyAscii, gstrNUMERIC_DIGITS)

'

If pintKeyValue < 32 _


32/59



Or InStr(pstrSearchString, Chr$(pintKeyValue)) > 0 Then

'Do nothing - i.e., accept the control character or any key

' in the search string passed to this function ...

Else

'cancel (do not accept) any other key ...

pintKeyValue = 0

End If

ValidKey = pintKeyValue

End Function

'------------------------------------------------------------------------

Public Function ConvertUpper(pintKeyValue As Integer) As Integer

'------------------------------------------------------------------------

' Common function to force alphabetic keyboard characters to uppercase

' when called from the KeyPress event.

' Typical call:

' KeyAscii = ConvertUpper(KeyAscii)

'

If Chr$(pintKeyValue) >= "a" And Chr$(pintKeyValue)


33/59



End Function

'-----------------------------------------------------------------------------

Public Sub SelectTextBoxText(pobjTextbox As TextBox)

'-----------------------------------------------------------------------------

With pobjTextbox

.SelStart = 0

.SelLength = Len(.Text)

End With

End Sub

'-----------------------------------------------------------------------------

Public Sub TabToNextTextBox(pobjTextBox1 As TextBox, pobjTextBox2 As TextBox)

'-----------------------------------------------------------------------------

If gblnPopulating Then Exit Sub

If pobjTextBox2.Enabled = False Then Exit Sub

If Len(pobjTextBox1.Text) = pobjTextBox1.MaxLength Then

pobjTextBox2.SetFocus

End If

End Sub

'-----------------------------------------------------------------------------

Public Function UnFormatNumber(pstrNumberIn As String) As String

'-----------------------------------------------------------------------------

Dim lngX As Long

Dim strCurrChar As String


34/59



Dim strNumberOut As String

strNumberOut = ""

For lngX = 1 To Len(pstrNumberIn)

strCurrChar = Mid$(pstrNumberIn, lngX, 1)

If InStr("0123456789.", strCurrChar) > 0 Then

strNumberOut = strNumberOut & strCurrChar

End If

Next

UnFormatNumber = strNumberOut

End Function

Code the General Declarations section as shown below. Here, as in the previous sample application, twoADO object variables, mobjADOConn and mobjADORst, are defined at the form level, as are some otherform-level variables that will be needed.

Option Explicit

Dim mobjADOConn As ADODB.Connection

Dim mobjADORst As ADODB.Recordset

Private mstrSQL As String

Private mdblMinAsking As Double

Private mblnUpdatePending As Boolean

Private mstrUpdateType As String

Private mavntUSStates As Variant

Code the Form_Load event as shown below. In it, a programmer-defined Sub named GetMinimumAskingis called (that routine is the one that displays the initial prompt to the user to enter the minimum asking priceof the properties they want to work with). Then, the variant array mavntUSStates is loaded with the 50 USstate abbreviations, needed for validating the state input by the user. This is followed by a call to theCenterForm sub. Then, the ADO connection object (mobjADOConn) is instantiated, its ConnectionString


35/59



property is set, and the Open methodis invoked so that we can use the Property database in the application.This is followed by a call to the programmer-defined Sub GetPropertyData (which runs the query to createthe recordset that will be used to browse the Property table records), followed by a call to the programmer-defined Sub SetFormState (which enables and disables controls at the appropriate time).

'-----------------------------------------------------------------------------

Private Sub Form_Load()

'-----------------------------------------------------------------------------


' obtain the minimum asking price for the properties to be worked with

GetMinimumAsking

' load the array of states to be used for validation

mavntUSStates = Array("AK", "AL", "AR", "AZ", "CA", "CO", "CT", "DC", _

"DE", "FL", "GA", "HI", "IA", "ID", "IL", "IN", _

"KS", "KY", "LA", "MA", "MD", "ME", "MI", "MN", _

"MO", "MS", "MT", "NC", "ND", "NE", "NH", "NJ", _

"NM", "NV", "NY", "OH", "OK", "OR", "PA", "RI", _

"SC", "SD", "TN", "TX", "UT", "VA", "VT", "WA", _

"WI", "WV", "WY")

'center the form:

CenterForm Me

' Connect to the Property database:

Set mobjADOConn = New ADODB.Connection

mobjADOConn.ConnectionString = "DSN=PropDB;Uid=admin;Pwd=;"

mobjADOConn.Open

Call GetPropertyData


36/59



SetFormState False

Exit Sub

LocalError:


End Sub

Code the GetMinimumAsking Sub, which uses the InputBox function to prompt to the user to enter the minimumasking price of the properties they want to work with. The resulting value is then stored in the form-level variable

mdblMinAsking.

'-----------------------------------------------------------------------------

Private Sub GetMinimumAsking()

'-----------------------------------------------------------------------------

Dim strInputBoxPrompt As String

Dim strAsking As String

strInputBoxPrompt = "Enter the minimum asking price (for example, 200000) " _

& "for the properties that you want to work with this session." _

& vbNewLine _

& "To work with ALL properties, leave the default of zero."

strAsking = InputBox(strInputBoxPrompt, "Minimum Asking Price", "0")

If strAsking = "" Then

' user clicked Cancel button on the input box, so end the app

End

End If


37/59



mdblMinAsking = Val(strAsking)

End Sub

Code the GetPropertyData Sub, which builds the SQL to get the property records meeting the minimum askingprice condition. The Recordset object is then instantiated, its CursorLocation property is set, and its Open methodis invoked to execute the SQL and return the resultset. This is done in a loop in case the resultset does not returnany records due to the fact no records in the table met the asking price condition. In that situation, the user isgiven the opportunity to specify a different asking price value. Following this, the programmer-defined SubPopulateFormFields is called (which displays the fields from the current record in their corresponding textboxeson the form).

'-----------------------------------------------------------------------------

Private Sub GetPropertyData()

'-----------------------------------------------------------------------------


Dim blnGotData As Boolean

blnGotData = False

Do

'select or reload the data to be displayed:

mstrSQL = "select propno" _

& " , empno" _

& " , address" _

& " , city" _

& " , state" _

& " , zip" _

& " , beds" _

& " , baths" _

& " , asking" _

& " from property" _


38/59



& " where asking >= " & mdblMinAsking _

& " order by propno"

Set mobjADORst = New ADODB.Recordset

mobjADORst.CursorLocation = adUseClient

mobjADORst.Open mstrSQL, mobjADOConn, adOpenDynamic, adLockOptimistic, adCmdText


If MsgBox("There are no properties with an asking price >= " _

& Format$(mdblMinAsking, "Currency") _

& ". Do you want to try again with a different value?", _

vbYesNo + vbQuestion, _

"Asking Price") _

= vbYes Then

GetMinimumAsking

Else

End

End If

Else

blnGotData = True

End If

Loop Until blnGotData


Call PopulateFormFields

Exit Sub

LocalError:



39/59



End Sub

Code the PopulateFormFields Sub, which assigns the fields from the current record to their correspondingtextboxes on the form. Note that the gblnPopulating Boolean variable is set to True prior to the assignments and

set to False after the assignments. This value is used to control whether or not certain code executes in the eventprocedures for some of these textboxes. The Sub SetRecNum is then called.

'-----------------------------------------------------------------------------

Private Sub PopulateFormFields()

'-----------------------------------------------------------------------------


gblnPopulating = True

'copy the data from the resultset to the text boxes:

txtPropNo.Text = mobjADORst.Fields("propno")

txtEmpNo.Text = mobjADORst.Fields("empno")

txtAddress.Text = mobjADORst.Fields("address")

txtCity.Text = mobjADORst.Fields("city")

txtState.Text = mobjADORst.Fields("state")

txtZip.Text = mobjADORst.Fields("zip")

txtBeds.Text = mobjADORst.Fields("beds")

txtBaths.Text = mobjADORst.Fields("baths")

txtAsking.Text = Format$(mobjADORst.Fields("asking"), "Currency")

gblnPopulating = False

Call SetRecNum


40/59



Exit Sub

LocalError:


End Sub

Code the SetRecNum Sub. This sub is identical to the one used in Sample Application 2. It displays the numberof the current record at the bottom of the screen using the AbsolutePosition and RowCount properties of theRecordset object.

'-----------------------------------------------------------------------------

Private Sub SetRecNum()

'-----------------------------------------------------------------------------

StatusBar1.SimpleText = "row " & mobjADORst.AbsolutePosition _

& " of " & mobjADORst.RecordCount

End Sub

Code the SetFormState Sub, which takes in a Boolean argument used to set the Enabled property of the controlson the form. Based on whether the value True or False is passed to this sub, this sub ensures that the textboxesare enabled for adds and updates and disabled for browsing; it also ensures that the various command buttonsare enabled or disabled at the appropriate time. This Sub also sets the form-level Boolean variablemblnUpdatePending.

'-----------------------------------------------------------------------------

Private Sub SetFormState(pblnEnabled As Boolean)

'-----------------------------------------------------------------------------

txtPropNo.Enabled = pblnEnabled

txtEmpNo.Enabled = pblnEnabled

txtAddress.Enabled = pblnEnabled

txtCity.Enabled = pblnEnabled


41/59



txtState.Enabled = pblnEnabled

txtZip.Enabled = pblnEnabled

txtBeds.Enabled = pblnEnabled

txtBaths.Enabled = pblnEnabled

txtAsking.Enabled = pblnEnabled

cmdSave.Enabled = pblnEnabled

cmdCancel.Enabled = pblnEnabled

cmdAdd.Enabled = Not pblnEnabled

cmdUpdate.Enabled = Not pblnEnabled

cmdDelete.Enabled = Not pblnEnabled

cmdExit.Enabled = Not pblnEnabled

cmdMoveFirst.Enabled = Not pblnEnabled

cmdMoveNext.Enabled = Not pblnEnabled

cmdMovePrevious.Enabled = Not pblnEnabled

cmdMoveLast.Enabled = Not pblnEnabled

mblnUpdatePending = pblnEnabled

End Sub

Code the Form_Unload event. In it, the form-level Boolean variable mblnUpdatePending is tested to see if(well, an update is pending i.e., whether an add or update is in progress). If the user is in the middle of an addor update and then clicks the "X" button on the upper-right corner of the form, they will receive the message thatthey must save or cancel prior to exiting the application, and the form will NOT be unloaded (because we areassigning a non-zero value to the Cancel argument in that situation). Provided that an add or update is not inprogress, we set the database objects to Nothing and the Unload will complete.

'-----------------------------------------------------------------------------

Private Sub Form_Unload(Cancel As Integer)


42/59



'-----------------------------------------------------------------------------

If mblnUpdatePending Then

MsgBox "You must save or cancel the current operation prior to exiting.", _

vbExclamation, _

"Exit"

Cancel = 1

Else

Set mobjADORst = Nothing

Set mobjADOConn = Nothing

End If

End Sub

Code the events for the various Textboxes as shown below. The code in these events ensure the following:

For all, highlight the text in the textbox when it receives focus.

For all but the last textbox, if the maximum number of characters typed into the textbox is reached, auto-tabto the next textbox.

Only numeric digits should be entered into the property number, employee number, zip codes, and bedstextboxes.

Only numeric digits and optionally one decimal point should be entered into the baths and asking textboxes.

Force uppercase on the state textbox.

When the asking textbox receives focus, the value in there should be unformatted. When the asking textboxloses focus, its value should be formatted as currency.

'-----------------------------------------------------------------------------

' Textbox events

'-----------------------------------------------------------------------------


43/59



' property #

Private Sub txtPropNo_GotFocus()

SelectTextBoxText txtPropNo

End Sub

Private Sub txtPropNo_KeyPress(KeyAscii As Integer)

KeyAscii = ValidKey(KeyAscii, gstrNUMERIC_DIGITS)

End Sub

Private Sub txtPropNo_Change()

TabToNextTextBox txtPropNo, txtEmpNo

End Sub

' emp #

Private Sub txtEmpNo_GotFocus()

SelectTextBoxText txtEmpNo

End Sub

Private Sub txtEmpNo_KeyPress(KeyAscii As Integer)


End Sub

Private Sub txtEmpNo_Change()

TabToNextTextBox txtEmpNo, txtAddress

End Sub

' address

Private Sub txtAddress_GotFocus()

SelectTextBoxText txtAddress


44/59



End Sub

Private Sub txtAddress_Change()

TabToNextTextBox txtAddress, txtCity

End Sub

' city

Private Sub txtCity_GotFocus()

SelectTextBoxText txtCity

End Sub

Private Sub txtCity_Change()

TabToNextTextBox txtCity, txtState

End Sub

' state

Private Sub txtState_GotFocus()

SelectTextBoxText txtState

End Sub

Private Sub txtState_KeyPress(KeyAscii As Integer)

KeyAscii = ConvertUpper(KeyAscii)

End Sub

Private Sub txtState_Change()

TabToNextTextBox txtState, txtZip

End Sub

' zip

Private Sub txtZip_GotFocus()


45/59



SelectTextBoxText txtZip

End Sub

Private Sub txtZip_KeyPress(KeyAscii As Integer)


End Sub

Private Sub txtZip_Change()

TabToNextTextBox txtZip, txtBeds

End Sub

' beds

Private Sub txtBeds_GotFocus()

SelectTextBoxText txtBeds

End Sub

Private Sub txtBeds_KeyPress(KeyAscii As Integer)


End Sub

Private Sub txtBeds_Change()

TabToNextTextBox txtBeds, txtBaths

End Sub

' baths

Private Sub txtBaths_GotFocus()

SelectTextBoxText txtBaths

End Sub

Private Sub txtBaths_KeyPress(KeyAscii As Integer)

KeyAscii = ValidKey(KeyAscii, gstrNUMERIC_DIGITS & ".")


46/59



' if text already has a decimal point, do not allow another ...

If Chr$(KeyAscii) = "." And InStr(txtBaths.Text, ".") > 0 Then

KeyAscii = 0

End If

End Sub

Private Sub txtBaths_Change()

TabToNextTextBox txtBaths, txtAsking

End Sub

' asking price

Private Sub txtAsking_GotFocus()

txtAsking.Text = UnFormatNumber(txtAsking.Text)

SelectTextBoxText txtAsking

End Sub

Private Sub txtAsking_KeyPress(KeyAscii As Integer)

KeyAscii = ValidKey(KeyAscii, gstrNUMERIC_DIGITS & ".")

' if text already has a decimal point, do not allow another ...

If Chr$(KeyAscii) = "." And InStr(txtAsking.Text, ".") > 0 Then

KeyAscii = 0

End If

End Sub

Private Sub txtAsking_LostFocus()

txtAsking.Text = Format$(txtAsking.Text, "Currency")

End Sub


47/59



Code the events for the navigation buttons as shown below, using the resultset "Move" methods to move to thefirst, last, next, or previous record, respectively.

'-----------------------------------------------------------------------------

Private Sub cmdMoveFirst_Click()

'-----------------------------------------------------------------------------




Exit Sub

LocalError:


End Sub

'-----------------------------------------------------------------------------

Private Sub cmdMoveLast_Click()

'-----------------------------------------------------------------------------


mobjADORst.MoveLast


Exit Sub

LocalError:


End Sub


48/59



'-----------------------------------------------------------------------------

Private Sub cmdMoveNext_Click()

'-----------------------------------------------------------------------------


mobjADORst.MoveNext


Beep

mobjADORst.MoveLast

End If


Exit Sub

LocalError:


End Sub

'-----------------------------------------------------------------------------

Private Sub cmdMovePrevious_Click()

'-----------------------------------------------------------------------------


mobjADORst.MovePrevious

If mobjADORst.BOF Then

Beep


End If


49/59




Exit Sub

LocalError:


End Sub

Code the Click event for the cmdAdd button. In it, the textboxes are cleared, the SetFormState sub is called(passing it a parameter of True, which will enable the textboxes and the Save and Cancel buttons and disable allthe other buttons), set the form-level variable mstrUpdateType to "A" (indicating that an add is pending) and setsfocus to the Property Number field.

'-----------------------------------------------------------------------------

Private Sub cmdAdd_Click()

'-----------------------------------------------------------------------------


'clear all the text boxes:

txtPropNo.Text = ""

txtEmpNo.Text = ""

txtAddress.Text = ""

txtCity.Text = ""

txtState.Text = ""

txtZip.Text = ""

txtBeds.Text = ""

txtBaths.Text = ""

txtAsking.Text = ""

SetFormState True


50/59



mstrUpdateType = "A"

txtPropNo.SetFocus

Exit Sub

LocalError:


End Sub

Code the Click event for the cmdUpdate button. In it, the SetFormState sub is called (passing it a parameter ofTrue, which will enable the textboxes and the Save and Cancel buttons and disable all the other buttons), set theform-level variable mstrUpdateType to "U" (indicating that an update is pending), disables the Property Numberfield (because it is the primary key and should not be changed) and sets focus to the Employee Number field.

'-----------------------------------------------------------------------------

Private Sub cmdUpdate_Click()

'-----------------------------------------------------------------------------


SetFormState True

mstrUpdateType = "U"

' being that propno is the primary key, it should not be updatable

txtPropNo.Enabled = False

txtEmpNo.SetFocus

Exit Sub

LocalError:


End Sub


51/59



Code the Click event for the cmdSave button. The user would click this button after they have completed entriesfor an add or update. This sub first invokes the ValidateAllFields function, which returns a Boolean indicatingwhether or not all entries passed their edit checks. If not, we exit the sub and the record is not saved; the userremains in "update pending" mode and has the opportunity to correct the entries. Provided that validation is

successful, the sub proceeds. The mstrUpdateType variable is checked to see whether we are dealing with anadd or an update.

If we are dealing with an add, we invoke the AddNew method of the Recordset object. The AddNew methodprepares a new row you can edit and subsequently add to the Recordset object using the Update method. Afteryou modify the new row, you must use the Update method to save the changes and add the row to the result set.No changes are made to the database until you use the Update method. (The Update method is invoked after thecontent of the textboxes has been assigned to the database fields.)

If we are dealing with an update, we can just start modifying the fields (provided an appropriate cursor type hasbeen selected) unlike DAO and RDO, ADO does not use an Edit method. Changes made to the current rowscolumns are copied to the copy buffer. After you make the desired changes to the row, use the Update method tosave your changes or the CancelUpdate method to discard them. (If you move on to another record without

invoking Update, your changes will be lost.)

The content of the textboxes is assigned to the database fields, then the Update method is invoked. The Updatemethod saves the contents of the copy buffer row to a specified updatable Recordset object and discards thecopy buffer.

The mstrUpdateType variable is checked once again, and if we are dealing with an add, there is some extrawork to do. Although the new record has been added, the original resultset still does not contain the new record.The Requery method must be invoked, which updates the data in a Recordset object by re-executing the queryon which the object is based. The Find method is then used to position to the new record. The ADO Find methodhas the following syntax:

RecordsetObject.Find Criteria, SkipRows, SearchDirection, Start

The Criteriaargument is a String value that specifies the column name, comparison operator, and value to use inthe search. Only a single-column name may be specified in criteria; multi-column searches are notsupported. The comparison operator may be ">" (greater than), "=" (greaterthan or equal), " #7/22/97#"). These values can contain hours, minutes, and seconds toindicate time stamps, but should not contain milliseconds or errors will occur. If the comparison operatoris "like", the string value may contain an asterisk (*) to find one or more occurrences of any character orsubstring. For example, "state like 'M*'" matches Maine and Massachusetts. You can also use leadingand trailing asterisks to find a substring contained within the values. For example, "state like '*as*'"matches Alaska, Arkansas, and Massachusetts. Asterisks can be used only at the end of a criteria string,or together at both the beginning and end of a criteria string, as shown above. You cannot use theasterisk as a leading wildcard ('*str'), or embedded wildcard ('s*r'). This will cause an error.

SkipRowsis an optional Long value, whose default is zero, that specifies the row offset from the current row (orbookmark row specified by the Startargument, if present) to begin the search. By default, the search willstart on the current row.


52/59



SearchDirectionis an optional value that determines in which direction the search is performed. The value isspecified by the constants adSearchForward (the default) or adSearchBackward, which equate tovalues of 1 or -1, respectively.

Startis an optional Variant bookmark that functions as the starting position for the search.

Note: Unlike DAO, ADO does not have a "NoMatch" property. If the ADO Find method is unsuccessful, the recordpointer is positioned at the end of the Recordset.

The SetRecNum sub is then be called to display the status bar information about the new record. TheSetFormState sub is then called with a parameter of False, which causes the textboxes and the Save and Cancelbuttons to be disabled and all other buttons to be enabled.

Note that in the statement that assigns the contents of the txtAsking textbox to the asking field of the table, ourUnFormatNumber function is used to strip off the non-numeric characters. This is because we are using adisplay format that includes a dollar sign and commas on the txtAsking control, and an error would occur if weattempted to assign this directly to the asking field, which is defined as numeric.

'-----------------------------------------------------------------------------

Private Sub cmdSave_Click()

'-----------------------------------------------------------------------------


If Not ValidateAllFields Then Exit Sub

If mstrUpdateType = "A" Then

mobjADORst.AddNew

Else

' We can just update the fields. No explicit Edit method

' is available or needed.

End If

'save the data to the database:

mobjADORst.Fields("propno") = txtPropNo.Text

mobjADORst.Fields("empno") = txtEmpNo.Text

mobjADORst.Fields("address") = txtAddress.Text


53/59



mobjADORst.Fields("city") = txtCity.Text

mobjADORst.Fields("state") = txtState.Text

mobjADORst.Fields("zip") = txtZip.Text

mobjADORst.Fields("beds") = txtBeds.Text

mobjADORst.Fields("baths") = txtBaths.Text

mobjADORst.Fields("asking") = UnFormatNumber(txtAsking.Text)

mobjADORst.Update


'after the new record is added, the db must be re-queried

'so that the resultset contains the new record:

mobjADORst.Requery

' reposition to the record just added

mobjADORst.Find "propno = " & txtPropNo.Text

'display status info about the new record

SetRecNum

End If

Reset:

SetFormState False

Exit Sub

LocalError:


Resume Reset

End Sub


54/59



Code the Click event for the cmdDelete button. The user is first asked to confirm that they want to delete therecord, and if so, the Delete method of the resultset object is invoked, which deletes the current row in anupdatable resultset object. The Requery method is then invoked so that the record is removed from the resultsetthat the user is working with. The Find method is then invoked to position the next record after the deleted one. Ifit was the last record that was deleted, then we position to the "new" last record using the MoveLast property.PopulateFormFields must then be called to display the contents of the new current record.

'-----------------------------------------------------------------------------

Private Sub cmdDelete_Click()

'-----------------------------------------------------------------------------


'when the current record is deleted, the current location in the recordset

'is invalid. use the Requery method to re-execute the query and update

'the data.

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

vbYesNo + vbQuestion, _

"Delete") = vbNo Then

Exit Sub

End If

mobjADORst.Delete

mobjADORst.Requery

' reposition to one past the record just deleted

mobjADORst.Find "propno > " & txtPropNo.Text

' If it was the last record that was deleted, the Find method will

' come back with EOF, in which case we should MoveLast to position

' us to the "new" last record ...

If mobjADORst.EOF Then mobjADORst.MoveLast

'load data into the text boxes:


55/59




Exit Sub

LocalError:


End Sub

The ValidateAllFields function, which returns a Boolean value indicating whether or not all fields have passedvalidation checks. This function calls upon two "helper" functions: PropertyExists and ValidState. When the useris doing an add, the PropertyExist function is called to see whether or not the proposed Property Number isalready being used in the Property table. If so, the user is informed that they can't use that number (because it is

the primary key and must be unique) and so they must use a different number. The ValidState routine is called toensure that the user has entered a valid US state. The code for all three functions is shown below.

'-----------------------------------------------------------------------------

Private Function ValidateAllFields() As Boolean

'-----------------------------------------------------------------------------

ValidateAllFields = False 'guilty until proven innocent


If txtPropNo.Text = "" Then

MsgBox "Property # must not be blank.", vbExclamation, "Property #"

txtPropNo.SetFocus

Exit Function

ElseIf PropertyExists Then

MsgBox "Property # already exists. Please use a different #.", _

vbExclamation, _

"Property #"

txtPropNo.SetFocus


56/59



Exit Function

End If

End If

If txtEmpNo.Text = "" Then

MsgBox "Emp # must not be blank.", vbExclamation, "Emp #"

txtEmpNo.SetFocus

Exit Function

End If

If txtAddress.Text = "" Then

MsgBox "Address must not be blank.", vbExclamation, "Address"

txtAddress.SetFocus

Exit Function

End If

If txtCity.Text = "" Then

MsgBox "City must not be blank.", vbExclamation, "City"

txtCity.SetFocus

Exit Function

End If

If Not ValidState Then

MsgBox "Missing or invalid state.", vbExclamation, "State"

txtState.SetFocus

Exit Function

End If

If txtZip.Text = "" Or Len(txtZip.Text) = 5 Then

' it's OK

Else


57/59



MsgBox "Zip code must either be blank or exactly 5 digits.", _

vbExclamation, _

"Zip Code"

txtZip.SetFocus

Exit Function

End If

If Val(txtBeds.Text) = 0 Then

MsgBox "Beds must not be zero.", vbExclamation, "Beds"

txtBeds.SetFocus

Exit Function

End If

If Val(txtBaths.Text) = 0 Then

MsgBox "Baths must not be zero.", vbExclamation, "Baths"

txtBaths.SetFocus

Exit Function

End If

If Val(UnFormatNumber(txtAsking.Text)) = 0 Then

MsgBox "Asking must not be zero.", vbExclamation, "Asking"

txtAsking.SetFocus

Exit Function

End If

' if we make it here, all fields have passed edit

ValidateAllFields = True

End Function

'--------------------------------------------------------------------------------


58/59



Private Function ValidState() As Boolean

'--------------------------------------------------------------------------------

Dim lngX As Long

Dim blnStateFound As Boolean

blnStateFound = False

For lngX = 0 To UBound(mavntUSStates)

If txtState.Text = mavntUSStates(lngX) Then

blnStateFound = True

Exit For

End If

Next

ValidState = blnStateFound

End Function

'-----------------------------------------------------------------------------

Private Function PropertyExists() As Boolean

'-----------------------------------------------------------------------------

Dim objTempRst As New ADODB.Recordset

Dim strSQL As String

strSQL = "select count(*) as the_count from property where propno = " &txtPropNo.Text

objTempRst.Open strSQL, mobjADOConn, adOpenForwardOnly, , adCmdText

If objTempRst("the_count") > 0 Then

PropertyExists = True


59/59


Else

PropertyExists = False

End If

End Function

Code the Click event for the cmdCancel button. The user would click this button if, during an add or update, theydecide to abandon the operation. Here, PopulateFormFields is called to reset the textboxes to their content priorto the user clicking the Add or Update button, and SetFormState is called with a parameter of False, whichcauses the textboxes and the Save and Cancel buttons to be disabled and all other buttons to be enabled.

'-----------------------------------------------------------------------------

Private Sub cmdCancel_Click()

'-----------------------------------------------------------------------------

PopulateFormFields

SetFormState False

End Sub

Code the Click event for the cmdExit button, which issues the Unload Me statement to fire the Form_Unloadevent, which will unload the form and end the application.

'-----------------------------------------------------------------------------

Private Sub cmdExit_Click()

'-----------------------------------------------------------------------------

Unload Me

End Sub


Documents

leccion 7 - usando ado