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Error Handling (2)
VB6 Database

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VB6 Database Example - Phone Directory - Managing the Database

1. Before starting, make a copy of your phone database file using the Windows Explorer. That way, in case we mess up, you still have a good copy. And, create a data link to the database. Here, we develop a simple DBMS for our phone number database. We will be able to display individual records and edit them. And, we will be able to add or delete records. Note this is a simple system and many of the fancy ‘bells and whistles’ (for example, asking if you really want to delete a record) that should really be here are not. Adding such amenities is left as an exercise to the student.

2. Load your last Books Database application (Example 8-2 - the one with the ‘Rolodex’ search). We will modify this application to fit the phone number DBMS. Resave your form and project with different names. Add three command buttons to the upper right corner of the form. Modify/set the following properties for each tool. For the data control and text boxes, make sure you follow the order shown.

*frmBooks (this is the old name):
Caption - Phone List
Name - frmPhone

*dtaTitles (this is the old name):
Caption - Phone Numbers
ConnectionString - [your phone database data link] (select, don’t type)
RecordSource - SELECT * FROM PhoneList ORDER BY Name (the ORDER keyword sorts the database by the given field)
Name - dtaPhone
LockType - adLockOptimistic

Caption - Description

Caption - Phone

Caption - Name

*txtAuthor (this is the old name):
DataSource - dtaPhone (select, don’t type)
DataField - Name (select, don’t type)
Locked - False
Name - txtName
MaxLength - 40
TabIndex - 1

*txtISBN (this is the old name):
DataSource - dtaPhone (select, don’t type)
DataField - Phone (select, don’t type)
Locked - False
Name - txtPhone
MaxLength - 15
TabIndex - 3

*txtTitle (this is the old name):
DataSource - dtaPhone (select, don’t type)
DataField - Description (select, don’t type)
Locked - False
Name - txtDesc
MaxLength - 40
TabIndex - 2

Caption - &Add
Name - cmdAdd

Caption - &Save
Enabled - False
Name - cmdSave

Caption - &Delete
Name - cmdDelete

When done, my form looked like this:

At this point, you can run your application and you should be able to navigate through your phone database using the data control. Don’t try any other options, though. We need to do some coding.

3. In Form_Load, replace the word frmBooks with frmPhone. This will allow the letter keys to be displayed properly.

4. In the cmdLetter_Click procedure, replace all occurrences of the word dtaTitles with dtaPhone. Replace all occurrences of Author with Name. The modified code will be:

Private Sub cmdLetter_Click(Index As Integer)
Dim BookMark1 As Variant
'Mark your place in case no match is found
BookMark1 = dtaPhone.Recordset.Bookmark
dtaPhone.Recordset.Find "Name >= '" + cmdLetter(Index).Caption + "'"
If dtaPhone.Recordset.EOF = True Then
dtaPhone.Recordset.Bookmark = BookMark1
End If
End Sub

5. Attach this code to the cmdAdd_Click procedure. This code invokes the code needed to add a record to the database. The Add and Delete buttons are disabled. Click the Save button when done adding a new record.

Private Sub cmdAdd_Click()
cmdAdd.Enabled = False
cmdSave.Enabled = True
cmdDelete.Enabled = False
End Sub

6. Add this code to the cmdSave_Click procedure. When done entering a new record, the command button status’s are toggled, the Recordset updated, and the data control Refresh method invoked to insure proper record sorting.

Private Sub cmdSave_Click()
cmdAdd.Enabled = True
cmdSave.Enabled = False
cmdDelete.Enabled = True
End Sub

7. Attach this code to the cmdDelete_Click procedure. This deletes the current record and moves to the next record. If we bump into the end of file, we need to check if there are no records remaining. If no records remain in the table, we display a message box. If records remain, we move around to the first record.

Private Sub cmdDelete_Click()
If dtaPhone.Recordset.EOF = True Then
If dtaPhone.Recordset.BOF = True Then
MsgBox "You must add a record.", vbOKOnly + vbInformation, "Empty file"
Call cmdAdd_Click
End If
End If
End Sub

8. Save the application. Try running it. Add records, delete records, edit records. If you’re really adventurous, you could add a button that dials your phone (via modem) for you! Look at the custom communications control.


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