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TreeNode Class

Represents a node of a TreeView.

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

public class TreeNode : MarshalByRefObject, ICloneable, 

The Nodes collection holds all the child TreeNode objects assigned to the current TreeNode. You can add, remove, or clone a TreeNode; when doing so, all child tree nodes are added, removed, or cloned. Each TreeNode can contain a collection of other TreeNode objects. This can make it difficult to determine where you are in the TreeView when iterating through the collection. To determine your location in a tree structure, use the FullPath property. The FullPath string can be parsed using the PathSeparator string value to determine where a TreeNode label begins and ends.

The TreeNode label is set by setting the Text property explicitly. The alternative is to create the tree node using one of the TreeNode constructors that has a string parameter that represents the Text property. The label is displayed next to the TreeNode image, if one is displayed.

To display images next to the tree nodes, assign an ImageList to the ImageList property of the parent TreeView control and assign an Image by referencing its index value in the ImageList property. Set the ImageIndex property to the index value of the Image you want to display when the TreeNode is in an unselected state. Likewise, set the SelectedImageIndex property to the index value of the Image you want to display when the TreeNode is selected.

Selecting specific tree nodes and iterating through the Nodes collection can be achieved by using the following property values: FirstNode, LastNode, NextNode, PrevNode, NextVisibleNode, PrevVisibleNode. Assign the TreeNode returned by one of aforementioned properties to the TreeView.SelectedNode property to select that tree node in the TreeView control.

Tree nodes can be expanded to display the next level of child tree nodes. The user can expand the TreeNode by pressing the plus (+) button next to the TreeNode, if one is displayed, or you can expand the TreeNode by calling the Expand method. To expand all child tree node levels in the Nodes collection, call the ExpandAll method. You can collapse the child TreeNode level by calling the Collapse method, or the user can press the minus (-) button next to the TreeNode, if one is displayed. You can also call the Toggle method to alternate the TreeNode between the expanded and collapsed states.

Tree nodes can optionally display a check box. To display the check boxes, set the CheckBoxes property of the TreeView to true. The Checked property is set to true for tree nodes that are in a checked state.

Notes to Inheritors:

Because the TreeNode class implements the ISerializable interface, derived classes intended to be serializable must also implement this interface and special constructors as described in Custom Serialization.

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 created an instance of a TreeView control on a Form.

// The basic Customer class. 
public class Customer : System.Object
   private string custName = "";
   protected ArrayList custOrders = new ArrayList();

   public Customer(string customername)
      this.custName = customername;

   public string CustomerName
      get{return this.custName;}
      set{this.custName = value;}

   public ArrayList CustomerOrders 
      get{return this.custOrders;}

} // End Customer class  

// The basic customer Order class. 
public class Order : System.Object
   private string ordID = "";

   public Order(string orderid)
      this.ordID = orderid;

   public string OrderID
      get{return this.ordID;}
      set{this.ordID = value;}

} // End Order class 

// 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.

   // Clear the TreeView each time the method is called.

   // 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)
           new TreeNode(customer2.CustomerName + "." + order1.OrderID));

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

   // Begin repainting the TreeView.

Any public static (Shared in Visual Basic) members of this type are thread safe. Any instance members are not guaranteed to be thread safe.

Windows 7, Windows Vista, Windows XP SP2, Windows XP Media Center Edition, Windows XP Professional x64 Edition, Windows XP Starter Edition, Windows Server 2008 R2, Windows Server 2008, Windows Server 2003, Windows Server 2000 SP4, Windows Millennium Edition, Windows 98, Windows CE, Windows Mobile for Smartphone, Windows Mobile for Pocket PC

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

.NET Framework

Supported in: 3.5, 3.0, 2.0, 1.1, 1.0

.NET Compact Framework

Supported in: 3.5, 2.0, 1.0