Computer Programming Concepts and Visual Basic David I. Schneider

population (in descending order). When an item in the list box is double-clicked, the list box’s Text property
is used to display the name of the country’s unit of currency in a label. (Recall that the value of the
Text property is the currently highlighted item.) The data control is made invisible since it is not needed
by the user.
Object Property Setting
frmCountries Caption Large Countries
datCountries Caption Countries
Database MEGACTY2.MDB
Name
Record Countries
Source
dblCountries RowSource datCountries
ListField Country
cmdSort Caption Sort by 1995
Population
lblCurrency Caption Currency:
lblUnit Caption (blank)
BorderStyle 1- Fixed Single
Private Sub CmdSort_Click()
datCountries.RecordSource = “SELECT * FROM Countries “ & _ “ORDER by pop1995
DESC”
datCountries.Refresh
End Sub
Private Sub dblCountries_dblClick()
datCountries.Recordset.FindFirst _
“Country =” & “‘“ & dblCountries.Text & “‘“
lblUnit.Caption = datCountries.Recordset.Fields(“currency”).Value
End Sub
[Run, click on the command button, and then double-click on Japan.]
When used to enhance data entry, a data-bound list or combo control is usually linked to two
data controls. The first data control is used to fill the list and the second to update a field in a
table. As demonstrated in Example 2, the first data control fills the list as designated by the
data-bound control’s ListField and RowSource properties. The second control updates a field in
a table specified by the data-bound control’s DataSource and DataField properties. Another
property of the data-bound control, the BoundColumn property, specifies the name of a field
in the first data control’s recordset. Once the user chooses one of the items in the list (and thereby
one of the rows), the value in the row’s specified field is passed to the field to be updated.
Usually, the BoundColumn property has the same setting as the DataField property.
EXAMPLE 3
Creating and Designing Databases 341
The following program adds cities to the Cities table of MEGACTY2.MDB. Of course, only cities in a
country found in the Countries table are acceptable. A data-bound combo box is employed to show the
user a list of the acceptable countries. (The experienced data-entry person can just type a name directly
into the text box portion of the combo box, whereas the novice must refer to the list.) When the program