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ListBox.BeginUpdate Method

Maintains performance while items are added to the ListBox one at a time by preventing the control from drawing until the EndUpdate method is called.

Namespace:  System.Windows.Forms
Assembly:  System.Windows.Forms (in System.Windows.Forms.dll)

'Declaration
Public Sub BeginUpdate

The preferred way to add multiple items to the ListBox is to use the AddRange method of the ListBox.ObjectCollection class (through the Items property of the ListBox). This enables you to add an array of items to the list in a single operation. However, if you want to add items one at a time using the Add method of the ListBox.ObjectCollection class, you can use the BeginUpdate method to prevent the control from repainting the ListBox each time an item is added to the list. Once you have completed the task of adding items to the list, call the EndUpdate method to enable the ListBox to repaint. This way of adding items can prevent flickered drawing of the ListBox when a large number of items are being added to the list.

The following code example uses the BeginUpdate and EndUpdate methods while adding five thousand items to a ListBox. This example requires that a ListBox control, named listBox1, has been added to a Form and that this method is placed within the form and called from it.

 Public Sub AddToMyListBox()
     ' Stop the ListBox from drawing while items are added.
     listBox1.BeginUpdate()

     ' Loop through and add five thousand new items. 
     Dim x As Integer 
     For x = 1 To 4999
         listBox1.Items.Add("Item " & x.ToString())
     Next x
     ' End the update process and force a repaint of the ListBox.
     listBox1.EndUpdate()
 End Sub

.NET Framework

Supported in: 4.6, 4.5, 4, 3.5, 3.0, 2.0, 1.1

.NET Framework Client Profile

Supported in: 4, 3.5 SP1
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