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TreeView.BeginUpdate Method

Disables any redrawing of the tree view.

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

Public Sub BeginUpdate

To maintain performance while items are added one at a time to the TreeView, call the BeginUpdate method. The BeginUpdate method prevents the control from painting until the EndUpdate method is called.

The preferred way to add items to a tree view control is to use the AddRange method to add an array of tree node items to a tree view. However, if you want to add items one at a time, use the BeginUpdate method to prevent the TreeView control from painting during the add operations. To allow the control to resume painting, call the EndUpdate method when all the tree nodes have been added to the tree view.

The following code example displays customer information in a TreeView control. The root tree nodes display customer names, and the child tree nodes display the order numbers assigned to each customer. In this example, 1,000 customers are displayed with 15 orders each. The repainting of the TreeView is suppressed by using the BeginUpdate and EndUpdate methods, and a wait Cursor is displayed while the TreeView creates and paints the TreeNode objects. This example requires that you have a Customer object that can hold a collection of Order objects. It also requires that you have a cursor file that is named MyWait.cur in the application directory and that you have created an instance of a TreeView control on a Form.

Public Class Customer
   Inherits [Object]
   Private custName As String = "" 
   Friend custOrders As New ArrayList()

   Public Sub New(ByVal customername As String)
      Me.custName = customername
   End Sub 

   Public Property CustomerName() As String 
         Return Me.custName
      End Get 
      Set(ByVal Value As String)
         Me.custName = Value
      End Set 
   End Property 

   Public ReadOnly Property CustomerOrders() As ArrayList
         Return Me.custOrders
      End Get 
   End Property 
End Class 'End Customer class

Public Class Order
   Inherits [Object]
   Private ordID As String 

   Public Sub New(ByVal orderid As String)
      Me.ordID = orderid
   End Sub 'New 

   Public Property OrderID() As String 
         Return Me.ordID
      End Get 
      Set(ByVal Value As String)
         Me.ordID = Value
      End Set 
   End Property 
End Class ' End Order class

' Create a new ArrayList to hold the Customer objects. 
Private customerArray As New ArrayList()

Private Sub FillMyTreeView()
   ' Add customers to the ArrayList of Customer objects. 
   Dim x As Integer 
   For x = 0 To 999
      customerArray.Add(New Customer("Customer" + x.ToString()))
   Next x

   ' Add orders to each Customer object in the ArrayList. 
   Dim customer1 As Customer
   For Each customer1 In customerArray
      Dim y As Integer 
      For y = 0 To 14
         customer1.CustomerOrders.Add(New Order("Order" + y.ToString()))
      Next y
   Next customer1

   ' Display a wait cursor while the TreeNodes are being created.
   Cursor.Current = New Cursor("MyWait.cur")

   ' Suppress repainting the TreeView until all the objects have been created.

   ' Clear the TreeView each time the method is called.

   ' Add a root TreeNode for each Customer object in the ArrayList. 
   Dim customer2 As Customer
   For Each customer2 In customerArray
      treeView1.Nodes.Add(New TreeNode(customer2.CustomerName))

      ' Add a child TreeNode for each Order object in the current Customer object. 
      Dim order1 As Order
      For Each order1 In customer2.CustomerOrders
         treeView1.Nodes(customerArray.IndexOf(customer2)).Nodes.Add( _
    New TreeNode(customer2.CustomerName + "." + order1.OrderID))
      Next order1
   Next customer2

   ' Reset the cursor to the default for all controls.
   Cursor.Current = System.Windows.Forms.Cursors.Default 

   ' Begin repainting the TreeView.
End Sub 'FillMyTreeView

.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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