ListBox en Visual Basic .NET

The ListBox control displays a list of items from which we can make a selection. We can select one or more than one of the items from the list. The ListBox control is based on the ListControl class which is based on the Control class. The image below displays a ListBox.

Notable Properties of the ListBox

In the Behavior Section

HorizontalScrollbar: Displays a horizontal scrollbar to the ListBox. Works when the ListBox has MultipleColumns.
MultiColumn: The default value is set to False. Set it to True if you want the list box to display multiple columns.
ScrollAlwaysVisible: Default value is set to False. Setting it to True will display both Vertical and Horizontal scrollbar always.
SelectionMode: Default value is set to one. Select option None if you do not any item to be selected. Select it to MultiSimple if you want multiple items to be selected. Setting it to MultiExtended allows you to select multiple items with the help of Shift, Control and arrow keys on the keyboard.
Sorted: Default value is set to False. Set it to True if you want the items displayed in the ListBox to be sorted by alphabetical order.

In the Data Section

Notable property in the Data section of the Properties window is the Items property. The Items property allows us to add the items we want to be displayed in the list box. Doing so is simple, click on the ellipses to open the String Collection Editor window and start entering what you want to be displayed in the ListBox. After entering the items click OK and doing that adds all the items to the ListBox.

ListBox Event

The default event of ListBox is the SelectedIndexChanged which looks like this in code:

Private Sub ListBox1_SelectedIndexChanged(ByVal sender As System.Object, _ ByVal e As System.EventArgs) Handles ListBox1.SelectedIndexChanged End Sub

Working with ListBoxes

Drag a TextBox and a ListBox control to the form and add some items to the ListBox with it's items property.

Referring to Items in the ListBox

Items in a ListBox are referred by index. When items are added to the ListBox they are assigned an index. The first item in the ListBox always has an index of 0 the next 1 and so on.

Code to display the index of an item

Private Sub ListBox1_SelectedIndexChanged(ByVal sender As System.Object, _ ByVal e As System.EventArgs) Handles ListBox1.SelectedIndexChanged TextBox1.Text = ListBox1.SelectedIndex 'using the selected index property of the list box to select the index End Sub

When you run the code and select an item from the ListBox, it's index is displayed in the textbox.

Counting the number of Items in a ListBox

Add a Button to the form and place the following code in it's click event.

Private Sub Button1_Click(ByVal sender As System.Object, ByVal e _ As System.EventArgs) Handles Button1.Click TextBox1.Text = ListBox1.Items.Count 'counting the number of items in the ListBox with the Items.Count End Sub

When you run the code and click the Button it will display the number of items available in the ListBox.

Code to display the item selected from ListBox in a TextBox

Private Sub ListBox1_SelectedIndexChanged(ByVal sender As System.Object,_ ByVal e As System.EventArgs) Handles ListBox1.SelectedIndexChanged TextBox1.Text = ListBox1.SelectedItem 'using the selected item property End Sub

When you run the code and click an item in the ListBox that item will be displayed in the TextBox.

Code to Remove items from a ListBox

You can remove all items or one particular item from the list box.

Code to remove a particular item

Private Sub Button1_Click(ByVal sender As System.Object, ByVal e _ As System.EventArgs) Handles Button1.Click ListBox1.Items.RemoveAt(4) 'removing an item by specifying it's index End Sub

Code to Remove all items

Private Sub Button1_Click(ByVal sender As System.Object, _
ByVal e As System.EventArgs) Handles Button1.Click
ListBox1.Items.Clear()
'using the clear method to clear the list box
End Sub

Fuente: http://www.startvbdotnet.com/controls/listbox.aspx