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ComboBox.BeginUpdate Method

Maintains performance when items are added to the ComboBox one at a time.

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

'Declaration
Public Sub BeginUpdate

This method prevents the control from painting until the EndUpdate method is called.

The preferred way to add items to the ComboBox is to use the AddRange method of the ComboBox.ObjectCollection class (through the Items property of the ComboBox). This enables you to add an array of items to the list at one time. However, if you want to add items one at a time using the Add method of the ComboBox.ObjectCollection class, you can use the BeginUpdate method to prevent the control from repainting the ComboBox 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 ComboBox to repaint. This way of adding items can prevent flicker during the drawing of the ComboBox when a large number of items are being added to the list.

The following code example shows the usage of the BeginUpdate and EndUpdate methods. The example is part of a complete code example in the ComboBox class overview.

Private Sub addGrandButton_Click(ByVal sender As Object, ByVal e As System.EventArgs)
    comboBox1.BeginUpdate()
    Dim I As Integer 
    For I = 0 To 1000
        comboBox1.Items.Add("New Item " + i.ToString())
    Next
    comboBox1.EndUpdate()
End Sub

.NET Framework

Supported in: 4.5.2, 4.5.1, 4.5, 4, 3.5, 3.0, 2.0, 1.1, 1.0

.NET Framework Client Profile

Supported in: 4, 3.5 SP1

Windows 8.1, Windows Server 2012 R2, Windows 8, Windows Server 2012, Windows 7, Windows Vista SP2, Windows Server 2008 (Server Core Role not supported), Windows Server 2008 R2 (Server Core Role supported with SP1 or later; Itanium not supported)

The .NET Framework does not support all versions of every platform. For a list of the supported versions, see .NET Framework System Requirements.

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