Maintains performance when items are added to the System.Windows.Forms.ComboBox one at a time.
This method prevents the control from painting until the ComboBox.EndUpdate method is called.
The preferred way to add items to the System.Windows.Forms.ComboBox is to use the System.Windows.Forms.ComboBox.ObjectCollection.AddRange(Object) method of the System.Windows.Forms.ComboBox.ObjectCollection class (through the ComboBox.Items property of the System.Windows.Forms.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 System.Windows.Forms.ComboBox.ObjectCollection.Add(object) method of the System.Windows.Forms.ComboBox.ObjectCollection class, you can use the ComboBox.BeginUpdate method to prevent the control from repainting the System.Windows.Forms.ComboBox each time an item is added to the list. Once you have completed the task of adding items to the list, call the ComboBox.EndUpdate method to enable the System.Windows.Forms.ComboBox to repaint. This way of adding items can prevent flicker during the drawing of the System.Windows.Forms.ComboBox when a large number of items are being added to the list.