样式如下图！
这种带三态复选框的TreeView可以显示出 下级节点是否全部选中，是否有选中，在很多应用程序的开发中都可能会用到！
代码如下：
// ---------------------------------------------------------------------------------------------
#region // Copyright (c) 2004, SIL International. All Rights Reserved. 
// <copyright from='2004' to='2004' company='SIL International'>// Copyright (c) 2004, SIL International. All Rights Reserved. // // Distributable under the terms of either the Common Public License or the// GNU Lesser General Public License, as specified in the LICENSING.txt file.// </copyright> 
#endregion// // File: TriStateTreeView.cs// Responsibility: Eberhard Beilharz/Tim Steenwyk// // <remarks>// </remarks>// ---------------------------------------------------------------------------------------------using System;using System.Collections;using System.ComponentModel;using System.Drawing;using System.Data;using System.Runtime.InteropServices;using System.Windows.Forms;namespace xxx{
/// ----------------------------------------------------------------------------------------
/// <summary> /// A tree view with tri-state check boxes /// </summary> /// <remarks> /// REVIEW: If we want to have icons in addition to the check boxes, we probably have to /// set the icons for the check boxes in a different way. The windows tree view control /// can have a separate image list for states. /// </remarks>
/// ---------------------------------------------------------------------------------------- public class TriStateTreeView : TreeView { private System.Windows.Forms.ImageList m_TriStateImages; private System.ComponentModel.IContainer components; /// <summary> /// The check state /// </summary> /// <remarks>The states corresponds to image index</remarks> public enum CheckState { /// <summary>greyed out</summary> GreyChecked = 0, /// <summary>Unchecked</summary> Unchecked = 1, /// <summary>Checked</summary> Checked = 2, } #region Redefined Win-API structs and methods /// <summary></summary> [StructLayout(LayoutKind.Sequential, Pack=1)] public struct TV_HITTESTINFO { /// <summary>Client coordinates of the point to test.</summary> public Point pt; /// <summary>Variable that receives information about the results of a hit test.</summary> public TVHit flags; /// <summary>Handle to the item that occupies the point.</summary> public IntPtr hItem; } /// <summary>Hit tests for tree view</summary> [Flags] public enum TVHit { /// <summary>In the client area, but below the last item.</summary> NoWhere = 0x0001, /// <summary>On the bitmap associated with an item.</summary> OnItemIcon = 0x0002, /// <summary>On the label (string) associated with an item.</summary> OnItemLabel = 0x0004, /// <summary>In the indentation associated with an item.</summary> OnItemIndent = 0x0008, /// <summary>On the button associated with an item.</summary> OnItemButton = 0x0010, /// <summary>In the area to the right of an item. </summary> OnItemRight = 0x0020, /// <summary>On the state icon for a tree-view item that is in a user-defined state.</summary> OnItemStateIcon = 0x0040, /// <summary>On the bitmap or label associated with an item. </summary> OnItem = (OnItemIcon | OnItemLabel | OnItemStateIcon), /// <summary>Above the client area. </summary> Above = 0x0100, /// <summary>Below the client area.</summary> Below = 0x0200, /// <summary>To the right of the client area.</summary> ToRight = 0x0400, /// <summary>To the left of the client area.</summary> ToLeft = 0x0800 } /// <summary></summary> public enum TreeViewMessages { /// <summary></summary> TV_FIRST = 0x1100, // TreeView messages /// <summary></summary> TVM_HITTEST = (TV_FIRST + 17), } /// <summary></summary> [DllImport("user32.dll", CharSet=CharSet.Auto)] private static extern int SendMessage(IntPtr hWnd, TreeViewMessages msg, int wParam, ref TV_HITTESTINFO lParam); #endregion #region Constructor and destructor /// ------------------------------------------------------------------------------------ /// <summary> /// Initializes a new instance of the <see cref="TriStateTreeView"/> class. /// </summary> /// ------------------------------------------------------------------------------------ public TriStateTreeView() { // This call is required by the Windows.Forms Form Designer. InitializeComponent(); ImageList = m_TriStateImages; ImageIndex = (int)CheckState.Unchecked; SelectedImageIndex = (int)CheckState.Unchecked; } /// ----------------------------------------------------------------------------------- /// <summary> /// Clean up any resources being used. /// </summary> /// <param name="disposing"><c>true</c> to release both managed and unmanaged /// resources; <c>false</c> to release only unmanaged resources. /// </param> /// ----------------------------------------------------------------------------------- protected override void Dispose( bool disposing ) { if( disposing ) { if(components != null) { components.Dispose(); } } base.Dispose( disposing ); } #endregion #region Component Designer generated code /// ----------------------------------------------------------------------------------- /// <summary> /// Required method for Designer support - do not modify /// the contents of this method with the code editor. /// </summary> /// ----------------------------------------------------------------------------------- private void InitializeComponent() { this.components = new System.ComponentModel.Container(); System.Resources.ResourceManager resources = new System.Resources.ResourceManager(typeof(TriStateTreeView)); this.m_TriStateImages = new System.Windows.Forms.ImageList(this.components); // // m_TriStateImages // this.m_TriStateImages.ImageSize = new System.Drawing.Size(16, 16); this.m_TriStateImages.ImageStream = ((System.Windows.Forms.ImageListStreamer)(resources.GetObject("m_TriStateImages.ImageStream"))); this.m_TriStateImages.TransparentColor = System.Drawing.Color.Magenta; } #endregion #region Overrides /// ------------------------------------------------------------------------------------ /// <summary> /// Called when the user clicks on an item /// </summary> /// <param name="e"></param> /// ------------------------------------------------------------------------------------ protected override void OnClick(EventArgs e) { base.OnClick (e); TV_HITTESTINFO hitTestInfo = new TV_HITTESTINFO(); hitTestInfo.pt = PointToClient(Control.MousePosition); SendMessage(Handle, TreeViewMessages.TVM_HITTEST, 0, ref hitTestInfo); if ((hitTestInfo.flags & TVHit.OnItemIcon) == TVHit.OnItemIcon) { TreeNode node = GetNodeAt(hitTestInfo.pt); if (node != null) ChangeNodeState(node); } } /// ------------------------------------------------------------------------------------ /// <summary> /// Toggle item if user presses space bar /// </summary> /// <param name="e"></param> /// ------------------------------------------------------------------------------------ protected override void OnKeyDown(KeyEventArgs e) { base.OnKeyDown (e); if (e.KeyCode == Keys.Space) { ChangeNodeState(SelectedNode); } } #endregion #region Private methods /// ------------------------------------------------------------------------------------ /// <summary> /// Checks or unchecks all children /// </summary> /// <param name="node"></param> /// <param name="state"></param> /// ------------------------------------------------------------------------------------ private void CheckNode(TreeNode node, CheckState state) { node.ImageIndex = (int)state; node.SelectedImageIndex = (int)state; foreach (TreeNode child in node.Nodes) CheckNode(child, state); } /// ------------------------------------------------------------------------------------ /// <summary> /// Called after a node changed its state. Has to go through all direct children and /// set state based on children's state. /// </summary> /// <param name="node">Parent node</param> /// ------------------------------------------------------------------------------------ private void ChangeParent(TreeNode node) { if (node == null) return; CheckState state = GetChecked(node.FirstNode); foreach (TreeNode child in node.Nodes) state &= GetChecked(child); InternalSetChecked(node, state); ChangeParent(node.Parent); } /// ------------------------------------------------------------------------------------ /// <summary> /// Handles changing the state of a node /// </summary> /// <param name="node"></param> /// ------------------------------------------------------------------------------------ private void ChangeNodeState(TreeNode node) { BeginUpdate(); CheckState newState; if (node.ImageIndex == (int)CheckState.Unchecked || node.ImageIndex < 0) newState = CheckState.Checked; else newState = CheckState.Unchecked; CheckNode(node, newState); ChangeParent(node.Parent); EndUpdate(); } /// ------------------------------------------------------------------------------------ /// <summary> /// Sets the checked state of a node, but doesn't deal with children or parents /// </summary> /// <param name="node">Node</param> /// <param name="state">The new checked state</param> /// ------------------------------------------------------------------------------------ private void InternalSetChecked(TreeNode node, CheckState state) { node.ImageIndex = (int)state; node.SelectedImageIndex = (int)state; } #endregion #region Public methods /// ------------------------------------------------------------------------------------ /// <summary> /// Gets the checked state of a node /// </summary> /// <param name="node">Node</param> /// <returns>The checked state</returns> /// ------------------------------------------------------------------------------------ public CheckState GetChecked(TreeNode node) { if (node.ImageIndex < 0) return CheckState.Unchecked; else return (CheckState)node.ImageIndex; } /// ------------------------------------------------------------------------------------ /// <summary> /// Sets the checked state of a node /// </summary> /// <param name="node">Node</param> /// <param name="state">The new checked state</param> /// ------------------------------------------------------------------------------------ public void SetChecked(TreeNode node, CheckState state) { InternalSetChecked(node, state); CheckNode(node, state); ChangeParent(node.Parent); } #endregion }}代码下载