Combo box and List box in VB.Net.ppt

Combo box and List box in VB.Net

1. Shri Shivaji Science College, Amravati
Department of Computer Science
Topic-VB.NET
Prepared By
Dr. Ujwala S. Junghare
Assistant Professor
Dept. of Computer Science

2. Combo box and List box

3. List Boxes:
•Listboxesdisplayalistofitemsfromwhichtheusercanselectoneormore.Ifthereare
toomanyitemstodisplayatonce,ascrollbarautomaticallyappearstolettheuserscroll
throughthelist.InVisualBasic.NET,eachiteminalistboxisitselfanobject.
•Itallowstheprogrammertoadditemsatdesigntimebyusingthepropertieswindowor
attheruntime.
•YoucancreatealistboxbydraggingaListBoxcontrolfromtheToolboxanddroppingit
ontheform.

4. You can populate the list box items either from the properties window or at runtime.
Properties of the ListBox Control:
Sr.No
.
Property & Description
1 AllowSelection
GetsavalueindicatingwhethertheListBoxcurrentlyenablesselectionoflistitems.
2 BorderStyle
Getsorsetsthetypeofborderdrawnaroundthelistbox.
3 ColumnWidth
Getsofsetsthewidthofcolumnsinamulticolumnlistbox.
4 HorizontalExtent
Getsorsetsthehorizontalscrollingareaofalistbox.
5 HorizontalScrollBar
Getsorsetsthevalueindicatingwhetherahorizontalscrollbarisdisplayedinthelistbox.

5. 6 ItemHeight
Getsorsetstheheightofaniteminthelistbox.
7 Items
Getstheitemsofthelistbox.
8 MultiColumn
Getsorsetsavalueindicatingwhetherthelistboxsupportsmultiple
columns.
9 ScrollAlwaysVisible
Getsorsetsavalueindicatingwhethertheverticalscrollbarisshown
atalltimes.
10SelectedIndex
Getsorsetsthezero-basedindexofthecurrentlyselectediteminalist
box.
11SelectedIndices
Getsacollectionthatcontainsthezero-basedindexesofallcurrently
selecteditemsinthelistbox.

6. 12 SelectedItem
Getsorsetsthecurrentlyselectediteminthelistbox.
13 SelectedItems
Getsacollectioncontainingthecurrentlyselecteditemsinthelistbox.
14 SelectedValue
GetsorsetsthevalueofthememberpropertyspecifiedbytheValueMemberproperty.
15 SelectionMode
Getsorsetsthemethodinwhichitemsareselectedinthelistbox.Thispropertyhas
values−
•None
•One
•MultiSimple
•MultiExtended
16 Sorted
Getsorsetsavalueindicatingwhethertheitemsinthelistboxaresortedalphabetically.
17 Text
Getsorsearchesforthetextofthecurrentlyselectediteminthelistbox.
18 TopIndex
Getsorsetstheindexofthefirstvisibleitemofalistbox.

7. Public Class Form1
Private Sub Form1_Load(sender As Object, e As EventArgs)
Handles MyBase.Load
' Set the caption bar text of the form.
Me.Text = "tutorialspont.com"
ListBox1.Items.Add("Canada")
ListBox1.Items.Add("USA")
ListBox1.Items.Add("UK")
ListBox1.Items.Add("Japan")
ListBox1.Items.Add("Russia")
ListBox1.Items.Add("China")
ListBox1.Items.Add("India")
End Sub
Private Sub Button1_Click(sender As Object, e As
EventArgs) Handles Button1.Click MsgBox("You have selected
" + ListBox1.SelectedItem.ToString()) End Sub
Private Sub ListBox1_SelectedIndexChanged(sender As
Object, e As EventArgs) Handles
ListBox1.SelectedIndexChanged
Label2.Text = ListBox1.SelectedItem.ToString()
End Sub
End Class

8. Private Sub Button1_Click(ByVal sender As System.Object, _ ByVal e As
System.EventArgs) Handles Button1.Click
ListBox1.BeginUpdate()
Dim intLoopIndex As Integer
For intLoopIndex = 1 To 20
ListBox1.Items.Add("Item " &intLoopIndex.ToString())
Next intLoopIndex
ListBox1.EndUpdate()
End Sub

9. Combo box

10. The ComboBox control is used to display a drop-down list of various items. It is a
combination of a text box in which the user enters an item and a drop-down list from
which the user selects an item.
Let's create a combo box by dragging a ComboBox control from the Toolbox and
dropping it on the form.
Sr.No. Property & Description
1 AllowSelection
Getsavalueindicatingwhetherthelistenablesselectionoflistitems.
2 AutoCompleteCustomSource
GetsorsetsacustomSystem.Collections.Specialized.StringCollectionto
usewhentheAutoCompleteSourcepropertyissettoCustomSource.
3 AutoCompleteMode
Getsorsetsanoptionthatcontrolshowautomaticcompletionworksfor
theComboBox.
4 AutoCompleteSource
Getsorsetsavaluespecifyingthesourceofcompletestringsusedfor
automaticcompletion.
5 DataBindings
Getsthedatabindingsforthecontrol.

11. 6 DataManager
GetstheCurrencyManagerassociatedwiththiscontrol.
7 DataSource
GetsorsetsthedatasourceforthisComboBox.
8 DropDownHeight
Getsorsetstheheightinpixelsofthedrop-downportionoftheComboBox.
9 DropDownStyle
Getsorsetsavaluespecifyingthestyleofthecombobox.
10 DropDownWidth
Getsorsetsthewidthoftheofthedrop-downportionofacombobox.
11 DroppedDown
Getsorsetsavalueindicatingwhetherthecomboboxisdisplayingitsdrop-downportion.
12 FlatStyle
GetsorsetstheappearanceoftheComboBox.
13 ItemHeight
Getsorsetstheheightofaniteminthecombobox.
14 Items
GetsanobjectrepresentingthecollectionoftheitemscontainedinthisComboBox.

12. 15 MaxDropDownItems
Getsorsetsthemaximumnumberofitemstobedisplayedinthedrop-downpartofthecombobox.
16 MaxLength
Getsorsetsthemaximumnumberofcharactersausercanenterintheeditableareaofthecombobox.
17 SelectedIndex
Getsorsetstheindexspecifyingthecurrentlyselecteditem.
18 SelectedItem
GetsorsetscurrentlyselecteditemintheComboBox.
19 SelectedText
GetsorsetsthetextthatisselectedintheeditableportionofaComboBox.
20 SelectedValue
GetsorsetsthevalueofthememberpropertyspecifiedbytheValueMemberproperty.
21 SelectionLength
Getsorsetsthenumberofcharactersselectedintheeditableportionofthecombobox.
22 SelectionStart
Getsorsetsthestartingindexoftextselectedinthecombobox.
23 Sorted
Getsorsetsavalueindicatingwhethertheitemsinthecomboboxaresorted.
24 Text
Getsorsetsthetextassociatedwiththiscontrol.

13. PictureBox Control
•ThePictureBoxcontrolisusedfordisplayingimagesontheform.TheImagepropertyof
thecontrolallowsyoutosetanimagebothatdesigntimeoratruntime.
•Let'screateapictureboxbydraggingaPictureBoxcontrolfromtheToolboxanddropping
itontheform.

14. Sr.No. Property & Description
1 AllowDrop
Specifieswhetherthepictureboxacceptsdatathatauserdragsonit.
2 ErrorImage
Getsorspecifiesanimagetobedisplayedwhenanerroroccursduringtheimage-loadingprocessor
iftheimageloadiscancelled.
3 Image
Getsorsetstheimagethatisdisplayedinthecontrol.
4 ImageLocation
GetsorsetsthepathortheURLfortheimagedisplayedinthecontrol.
5 InitialImage
Getsorsetstheimagedisplayedinthecontrolwhenthemainimageisloaded.
PropertiesofthePictureBoxControl
ThefollowingaresomeofthecommonlyusedpropertiesofthePictureBoxcontrol−

15. 6 SizeMode
Determinesthesizeoftheimagetobedisplayedinthecontrol.Thispropertytakesitsvaluefromthe
PictureBoxSizeModeenumeration,whichhasvalues−
•Normal−theupperleftcorneroftheimageisplacedatupperleftpartofthepicturebox
•StrechImage−allowsstretchingoftheimage
•AutoSize−allowsresizingthepictureboxtothesizeoftheimage
•CenterImage−allowscenteringtheimageinthepicturebox
•Zoom−allowsincreasingordecreasingtheimagesizetomaintainthesizeratio.
7 TabIndex
Getsorsetsthetabindexvalue.
8 TabStop
SpecifieswhethertheuserwillbeabletofocusonthepictureboxbyusingtheTABkey.
9 Text
Getsorsetsthetextforthepicturebox.
10 WaitOnLoad
Specifieswhetherornotanimageisloadedsynchronously.

16. Sr.
No.
Method Name & Description
1CancelAsync
Cancelsanasynchronousimageload.
2Load
Displaysanimageinthepicturebox
3LoadAsync
Loadsimageasynchronously.
4ToString
Returnsthestringthatrepresentsthecurrentpicturebox.
MethodsofthePictureBoxControl
ThefollowingaresomeofthecommonlyusedmethodsofthePictureBoxcontrol−

17. PrivateSubButton1_Click(senderAsObject,eAsEventArgs)HandlesButton1.Click
'DimStrAsString="C:\Users\AMITYADAV\Desktop\"
PictureBox1.Image=Image.FromFile("C:\Users\AMITYADAV\Desktop\jtp2.png")
PictureBox1.SizeMode=PictureBoxSizeMode.StretchImage
PictureBox1.Height=250
PictureBox1.Width=400
Label1.Visible=False
EndSub

18. Timer Control -VB.Net
WhatisTimerControl?
TimerControlplaysanimportantroleintheClientsideprogrammingandServersideprogramming,alsousedinWindowsServices.
ByusingthisTimerControl,windowsallowyoutocontrolwhenactionstakeplacewithouttheinteractionofanotherthread.
UseofTimerControl
WecanuseTimerControlinmanysituationsinourdevelopmentenvironment.Ifyouwanttorunsomecode
afteracertainintervaloftimecontinuously,youcanusetheTimercontrol.Aswellastostartaprocessatafixed
timeschedule,toincreaseordecreasethespeedinananimationgraphicswithtimescheduleetc.youcanusethe
TimerControl.TheVisualStudiotoolboxhasaTimerControlthatallowingyoutodraganddropthetimer
controlsdirectlyontoaWindowsFormsdesigner.Atruntimeitdoesnothaveavisualrepresentationandworks
asacomponentinthebackground.

19. HowtoTimerControl?
WiththeTimerControl,wecancontrolprogramsinmillisecond,seconds,minutesandevenin
hours.TheTimerControlallowsustosetIntervalpropertyinmilliseconds(1secondisequalto
1000milliseconds).Forexample,ifwewanttosetanintervaloftwominutewesetthevalueat
Intervalpropertyas120000,means120x1000.
TheTimerControlstartsitsfunctioningonlyafteritsEnabledpropertyissettoTrue,bydefault
EnabledpropertyisFalse.