1. The document discusses various list box and combo box controls in Visual Basic 6. It describes the different styles of combo boxes and how to add, remove, and clear items from list boxes and combo boxes at both design-time and run-time. 2. It also covers list box and combo box properties like ListIndex, ListCount, and List as well as looping structures like Do/Loop and For/Next loops. 3. The document provides examples of using string functions like Left, Right, Mid, Len, InStr, LTrim, RTrim, and Trim in Visual Basic code. It concludes with a sample application demonstrating the use of list boxes and combo boxes.

1. VISUAL BASIC 6 – 3 CUBE COMPUTER INSTITUTE (3CCI)
Chapter 7
List Box Control
A list box control displays a list of items from which the user can select one or more.
List boxes present a list of choices to the user. By default, the choices are displayed vertically in
a single column.
If the number of items exceeds what can be displayed in the list box, scroll bars automatically
appear on the control. The user can then scroll up and down, or left to right through the list.
Combo Box Control
A combo box control combines the features of a text box and a list box. This control allows the
user to select an item either by typing text into the combo box, or by selecting it from the list.
Combo boxes present a list of choices to the user. If the number of items exceeds what can be
displayed in the combo box, scroll bars will automatically appear on the control. The user can
then scroll up and down or left to right through the list.
Combo Box Styles
There are three combo box styles. Each style can be set at design time and uses values, or
equivalent Visual Basic constants, to set the style of the combo box.
Style Value Constant
Drop-down combo box 0 vbComboDropDown
Simple combo box 1 vbComboSimple
Drop-down list box 2 vbComboDropDownList
1. Drop-down Combo Box
With the default setting (Style = 0 – Dropdown Combo), a combo box is a drop-down
combo box. The user can either enter text directly (as in a text box) or click the detached
arrow at the right of the combo box to open a list of choices. Selecting one of the choices
inserts it into the text portion at the top of the combo box.
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2. VISUAL BASIC 6 – 3 CUBE COMPUTER INSTITUTE (3CCI)
2. Simple Combo Box
Setting the Style property of a combo box to 1 – Simple Combo specifies a simple combo
box in which the list is displayed at all times. To display all entries in the list, you must draw
the list box large enough to display the entries. A vertical scroll bar is automatically inserted
when there are more entries than can be displayed. The user can still enter text directly or
select from the list. As with a drop-down combo box, a simple combo box also allows users
to enter choices not on the list.
3. Drop-down List Box
A drop-down list box (Style = 2 – Dropdown List) is like a regular list box — it displays a
list of items from which a user must choose. Unlike list boxes, however, the list is not
displayed until you click the arrow to the right of the box. The key difference between this
and a drop-down combo box is that the user can't type into the box, he can only select
an item from the list.
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3. VISUAL BASIC 6 – 3 CUBE COMPUTER INSTITUTE (3CCI)
Adding Items to list Box / Combo Box at Design-Time:
1. Place the list box/ Combo box in form and choose the list box/ Combo box.
2. Go to list property of List Box Control/ Combo box Control.
3. Add 1st item to the list box/ Combo box.
4. To add 2nd item press Ctrl + Enter.
5. Repeat 4th step for adding more items to the list.
6. After Last item is added, don’t press Ctrl + Enter, otherwise at the end of list box/ Combo
box an empty string will be added.
Adding Items to list Box / Combo Box at Run-Time:
If you want to add item in the list box/ Combo Box during runtime, you have to use the Addtem
method.
General form – Object.AddItem Value [, Index]
Value is the value to add to the list. If the value is a string literal, enclose it in quotation marks.
Index specifies the position in the list where the value must be stored, the first element in the
list box has the Index = 0.
Example: lstName.AddItem “A”
cboName.AddItem “B”
Clearing The List Box/ Combo Box Items:
To clear items of the list box or a combo box at runtime, use the Clear Method to empty the
combo box and list box.
General form – Object.Clear
Example: lstName.Clear
cboName.Clear
ListIndex Property
Returns or sets the index of the currently selected item in the control. Not available at design
time.
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4. VISUAL BASIC 6 – 3 CUBE COMPUTER INSTITUTE (3CCI)
When a project is running, the user select an item from the list box/combo box, the index of
that selected item is stored in the ListIndex property.
ListIndex of the first item in the list is 0.
If no list item is selected then the ListIndex property is set to -1.
Example:
Private Sub cmdOk_Click ()
MsgBox cboName.ListIndex
End Sub
ListCount Property
The ListCount property of a list box/combo box is used to store the number of items in the list.
ListCount is always one more that the highest ListIndex, since ListIndex starts from 0.
Example:
Private Sub Form_Load()
Combo1.AddItem "A"
Combo1.AddItem "B"
Combo1.AddItem "C"
Combo1.AddItem "D"
End Sub
Private Sub cmdOk_Click ()
MsgBox cboName.ListCount
End Sub
List Property
The List Property is used to display a item from the list. The list property of list box/combo box
holds the text of all list elements.
Specify the element by using its Index.
General form –Object.List(Index) [ = Value]
Example:
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5. VISUAL BASIC 6 – 3 CUBE COMPUTER INSTITUTE (3CCI)
Private Sub Command1_Click()
MsgBox Combo1.List(Combo1.ListIndex) ‘gets the current selected item
End Sub
RemoveItem Property
The RemoveItem Property is used to remove a single element from the list.
General form – Object.RemoveItem Index.
The index is required as it specifies which item is to be removed.
Example:
Private Sub Command1_Click()
Combo1.RemoveItem Combo1.ListIndex ‘removes the current selected item
End Sub
Do/Loops
The process of repeating a series of instructions is called Looping. The group of repeated
instructions is called a loop.
An iteration is a single execution of the statements in the loop.
A Do/Loop terminates on the condition that you specify. Execution of a Do/Loop continues
while a condition is True or until a condition is true.
The first form of the Do/loop tests for completion at the top of the loop. This type of loop is
called as pretest. The statements inside the loop may never be executed if the terminating
condition is true the first time it is tested.
Syntax
Do [{While | Until} condition]
[statements]
[Exit Do]
[statements]
Loop
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6. VISUAL BASIC 6 – 3 CUBE COMPUTER INSTITUTE (3CCI)
The second form of Do/Loop tests for completion at the bottom of the loop. This type of loop is
called as posttest. Which means the statements of the loop will always be executed at least once.
Syntax
Do
[statements]
[Exit Do]
[statements]
Loop [{While | Until} condition]
The Do Loop statement syntax has these parts:
Part Description
condition Optional. Numeric expression or string expression that is True or False.
If condition is Null, condition is treated as False.
statements One or more statements that are repeated while, or until, condition is
True.
For...Next Statement
Repeats a group of statements a specified number of times.
Syntax
For counter = start To end [Step step]
[statements]
[Exit For]
[statements]
Next [counter]
The For…Next statement syntax has these parts:
Part Description
Counter Required. Numeric variable used as a loop counter.
start Required. Initial value of counter.
end Required. Final value of counter.
step Optional. Amount counter is changed each time through the loop. If not
specified, step defaults to one.
statements Optional. One or more statements between For and Next that are
executed the specified number of times.
Remarks
The step argument can be either positive or negative.
After all statements in the loop have executed, step is added to counter. At this point, either the
statements in the loop execute again (based on the same test that caused the loop to execute
initially), or the loop is exited and execution continues with the statement following the Next
statement.
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7. VISUAL BASIC 6 – 3 CUBE COMPUTER INSTITUTE (3CCI)
String Function
1. Left Function
Returns a Variant (String) containing a specified number of characters from the left side of a string.
Syntax
Left(string, length)
The Left function syntax has these named arguments:
Part Description
string Required. String expression from which the leftmost characters are returned. If string
contains Null, Null is returned.
length Required; Variant (Long). Numeric expression indicating how many characters to
return. If 0, a zero-length string ("") is returned. If greater than or equal to the number
of characters in string, the entire string is returned.
Left Function Example
This example uses the Left function to return a specified number of characters from the left
side of a string.
Dim AnyString, MyStr
AnyString = "Hello World" ' Define string.
MyStr = Left(AnyString, 1) ' Returns "H".
MyStr = Left(AnyString, 7) ' Returns "Hello W".
MyStr = Left(AnyString, 20) ' Returns "Hello World".
2. Right Function
Returns a Variant (String) containing a specified number of characters from the right side of a
string.
Syntax
Right(string, length)
The Right function syntax has these named arguments:
Part Description
string Required. String expression from which the rightmost characters are returned. If
string contains Null, Null is returned.
length Required; Variant (Long). Numeric expression indicating how many characters to
return. If 0, a zero-length string ("") is returned. If greater than or equal to the
number of characters in string, the entire string is returned.
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8. VISUAL BASIC 6 – 3 CUBE COMPUTER INSTITUTE (3CCI)
Right Function Example
This example uses the Right function to return a specified number of characters from the right
side of a string.
Dim AnyString, MyStr
AnyString = "Hello World" ' Define string.
MyStr = Right(AnyString, 1) ' Returns "d".
MyStr = Right(AnyString, 6) ' Returns " World".
MyStr = Right(AnyString, 20) ' Returns "Hello World".
3. Mid Function
Returns a Variant (String) containing a specified number of characters from a string.
Syntax
Mid(string, start[, length])
The Mid function syntax has these named arguments:
Part Description
string Required. String expression from which characters are returned. If string contains
Null, Null is returned.
start Required; Long. Character position in string at which the part to be taken begins. If
start is greater than the number of characters in string, Mid returns a zero-length
string ("").
length Optional; Variant (Long). Number of characters to return. If omitted or if there are
fewer than length characters in the text (including the character at start), all
characters from the start position to the end of the string are returned.
Mid Function Example
The first example uses the Mid function to return a specified number of characters from a
string.
Dim MyString, FirstWord, LastWord, MidWords
MyString = "Mid Function Demo" ' Create text string.
FirstWord = Mid(MyString, 1, 3) ' Returns "Mid".
LastWord = Mid(MyString, 14, 4) ' Returns "Demo".
MidWords = Mid(MyString, 5) ' Returns "Function Demo".
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9. VISUAL BASIC 6 – 3 CUBE COMPUTER INSTITUTE (3CCI)
4. Len Function
Returns a Long containing the number of characters in a string or the number of bytes required
to store a variable.
Syntax
Len(string | varname)
The Len function syntax has these parts:
Part Description
string Any valid string expression. If string contains Null, Null is returned.
Varname Any valid variable name. If varname contains Null, Null is returned. If varname is
a Variant, Len treats it the same as a String and always returns the number of
characters it contains.
Len Function Example
The first example uses Len to return the number of characters in a string or the number of bytes
required to store a variable.
Dim MyString, MyLen
MyString = "Hello World" ' Initialize variable.
MyLen = Len(MyString) ' Returns 11.
5. InStr Function
Returns a Variant (Long) specifying the position of the first occurrence of one string within another.
Syntax: InStr([start, ]string1, string2)
The InStr function syntax has these arguments:
Part Description
start Optional. Numeric expression that sets the starting position for each search. If
omitted, search begins at the first character position. If start contains Null, an
error occurs. The start argument is required if compare is specified.
string1 Required. String expression being searched.
string2 Required. String expression sought.
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10. VISUAL BASIC 6 – 3 CUBE COMPUTER INSTITUTE (3CCI)
InStr Function Example
This example uses the InStr function to return the position of the first occurrence of one string
within another.
Dim SearchString, SearchChar, MyPos
SearchString ="XXpXXpXXPXXP" ' String to search in.
SearchChar = "P" ' Search for "P".
' A textual comparison starting at position 4. Returns 6.
MyPos = Instr(4, SearchString, SearchChar, 1)
' A binary comparison starting at position 1. Returns 9.
MyPos = Instr(1, SearchString, SearchChar, 0)
' Comparison is binary by default (last argument is omitted).
MyPos = Instr(SearchString, SearchChar) ' Returns 9.
MyPos = Instr(1, SearchString, "W") ' Returns 0.
6. LTrim, RTrim, and Trim Functions
Returns a Variant (String) containing a copy of a specified string without leading spaces
(LTrim), trailing spaces (RTrim), or both leading and trailing spaces (Trim).
Syntax
LTrim(string)
RTrim(string)
Trim(string)
The required string argument is any valid string expression. If string contains Null, Null is
returned.
LTrim, RTrim, and Trim Functions Example
This example uses the LTrim function to strip leading spaces and the RTrim function to strip
trailing spaces from a string variable. It uses the Trim function to strip both types of spaces.
Dim MyString, TrimString
MyString = " <-Trim-> " ' Initialize string.
TrimString = LTrim(MyString) ' TrimString = "<-Trim-> ".
TrimString = RTrim(MyString) ' TrimString = " <-Trim->".
TrimString = LTrim(RTrim(MyString)) ' TrimString = "<-Trim->".
' Using the Trim function alone achieves the same result.
TrimString = Trim(MyString) ' TrimString = "<-Trim->".
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11. VISUAL BASIC 6 – 3 CUBE COMPUTER INSTITUTE (3CCI)
SAMPLE APPLICATION
Private Sub cmdAddCoffee_Click()
'Add a new coffee flavor to the coffee list
If cboCoffee.Text <> "" Then
With cboCoffee
.AddItem .Text
.Text = ""
End With
Else
MsgBox "Entere a coffee name to add", vbExclamation, "Missing Data"
End If
cboCoffee.SetFocus
End Sub
Private Sub mnuEditAdd_Click(Index As Integer)
'Add a new coffee to list
cmdAddCoffee_Click
End Sub
Private Sub mnuEditClear_Click(Index As Integer)
'Clear the coffee list
Dim intResponse As Integer
intResponse = MsgBox("Clear the coffee flavor list?", _
vbYesNo + vbQuestion, "Clear coffee list")
If intResponse = vbYes Then
cboCoffee.Clear
End If
End Sub
Private Sub mnuEditCount_Click(Index As Integer)
'Display a count of the coffee list
MsgBox "The number of coffee types is " & cboCoffee.ListCount
End Sub
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12. VISUAL BASIC 6 – 3 CUBE COMPUTER INSTITUTE (3CCI)
Private Sub mnuEditRemove_Click(Index As Integer)
'Remove the selected coffee from list
If cboCoffee.ListIndex <> -1 Then
cboCoffee.RemoveItem cboCoffee.ListIndex
Else
MsgBox "First select the coffee to remove", vbInformation, _
"No selection made"
End If
End Sub
Private Sub mnuFileExit_Click(Index As Integer)
'Terminate the Project
End
End Sub
Private Sub mnuFilePrintAll_Click(Index As Integer)
'Print the contents of the coffee flavors combo box on the printer
Dim intIndex As Integer
Dim intFinalValue As Integer
Printer.Print 'Blank Line
Printer.Print Tab(20); "Coffee Flavors"
Printer.Print 'Blank Line
intFinalValue = cboCoffee.ListCount - 1
'List index starts at 0
For intIndex = 0 To intFinalValue
Printer.Print Tab(20); cboCoffee.List(intIndex)
Next intIndex
Printer.EndDoc
End Sub
Private Sub mnuFilePrintSelect_Click(Index As Integer)
'Send the current selection of coffee flavor
'and syrup flavor to the printer
If cboCoffee.ListIndex <> -1 And lstSyrup.ListIndex <> -1 Then
Printer.Print 'Blank Line
Printer.Print Tab(15); "Coffee Selection"
Printer.Print 'Blank Line
Printer.Print Tab(10); "Coffee Flavor: "; cboCoffee.Text
Printer.Print 'Blank Line
Printer.Print Tab(10); "Syrup Flavor: "; lstSyrup.Text
Else
MsgBox "Make a selection for coffee and syrup.", vbExclamation, _
"Missing Data"
End If
End Sub
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