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TreeView.BeginUpdate Method

Disables any redrawing of the tree view.

[Visual Basic]
Public Sub BeginUpdate()
[C#]
public void BeginUpdate();
[C++]
public: void BeginUpdate();
[JScript]
public function BeginUpdate();

Remarks

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 control the control to resume painting, call the EndUpdate method when all the tree nodes have been added to the tree view.

Example

[Visual Basic, C#, C++] The following 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 assumes you have a Customer object that can hold a collection of Order objects. It also assumes that you have a cursor file named MyWait.cur in the application directory and that you have created an instance of a TreeView control on a Form.

[Visual Basic] 
' 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.
   treeView1.BeginUpdate()

   ' Clear the TreeView each time the method is called.
   treeView1.Nodes.Clear()

   ' 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.
   treeView1.EndUpdate()
End Sub 'FillMyTreeView

[C#] 
// Create a new ArrayList to hold the Customer objects.
private ArrayList customerArray = new ArrayList(); 

private void FillMyTreeView()
{
   // Add customers to the ArrayList of Customer objects.
   for(int x=0; x<1000; x++)
   {
      customerArray.Add(new Customer("Customer" + x.ToString()));
   }

   // Add orders to each Customer object in the ArrayList.
   foreach(Customer customer1 in customerArray)
   {
      for(int y=0; y<15; y++)
      {
         customer1.CustomerOrders.Add(new Order("Order" + y.ToString()));    
      }
   }

   // 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.
   treeView1.BeginUpdate();

   // Clear the TreeView each time the method is called.
   treeView1.Nodes.Clear();

   // Add a root TreeNode for each Customer object in the ArrayList.
   foreach(Customer customer2 in customerArray)
   {
      treeView1.Nodes.Add(new TreeNode(customer2.CustomerName));
          
      // Add a child treenode for each Order object in the current Customer object.
      foreach(Order order1 in customer2.CustomerOrders)
      {
         treeView1.Nodes[customerArray.IndexOf(customer2)].Nodes.Add(
           new TreeNode(customer2.CustomerName + "." + order1.OrderID));
      }
   }

   // Reset the cursor to the default for all controls.
   Cursor.Current = Cursors.Default;

   // Begin repainting the TreeView.
   treeView1.EndUpdate();
}

[C++] 
void FillMyTreeView() {
    // Add customers to the ArrayList of Customer objects.
    for (int x=0; x<1000; x++) {
        customerArray->Add(new Customer(String::Concat(S"Customer ", __box(x))));
    }

    // Add orders to each Customer object in the ArrayList.
    IEnumerator* myEnum = customerArray->GetEnumerator();
    while (myEnum->MoveNext()) {
        Customer* customer1 = __try_cast<Customer*>(myEnum->Current);

        for (int y=0; y<15; y++) {
            customer1->CustomerOrders->Add(new Order(String::Concat(S"Order ", __box(y))));
        }
    }

    // Display a wait cursor while the TreeNodes are being created.
    Cursor::Current = new System::Windows::Forms::Cursor(S"MyWait.cur");

    // Suppress repainting the TreeView until all the objects have been created.
    treeView1->BeginUpdate();

    // Clear the TreeView each time the method is called.
    treeView1->Nodes->Clear();

    // Add a root TreeNode for each Customer object in the ArrayList.
    while (myEnum->MoveNext()) {
        Customer* customer2 = __try_cast<Customer*>(myEnum->Current);

        treeView1->Nodes->Add(new TreeNode(customer2->CustomerName));

        // Add a child treenode for each Order object in the current Customer object.
        IEnumerator* myEnum = customer2->CustomerOrders->GetEnumerator();
        while (myEnum->MoveNext()) {
            Order* order1 = __try_cast<Order*>(myEnum->Current);

            treeView1->Nodes->Item[customerArray->IndexOf(customer2)]->Nodes->Add(
                new TreeNode(String::Concat(customer2->CustomerName, S".", order1->OrderID)));
        }
    }

    // Reset the cursor to the default for all controls.
    Cursor::Current = Cursors::Default;

    // Begin repainting the TreeView.
    treeView1->EndUpdate();
}

[JScript] No example is available for JScript. To view a Visual Basic, C#, or C++ example, click the Language Filter button Language Filter in the upper-left corner of the page.

Requirements

Platforms: Windows 98, Windows NT 4.0, Windows Millennium Edition, Windows 2000, Windows XP Home Edition, Windows XP Professional, Windows Server 2003 family, .NET Compact Framework

See Also

TreeView Class | TreeView Members | System.Windows.Forms Namespace | EndUpdate

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