' 导入命名空间
Imports System.Drawing
Imports System.Windows.Forms

Public Class Form1
    Inherits Form
    Private treeView1 As TreeView
    Private showCheckedNodesButton As Button

    Public Sub New()
        treeView1 = New TreeView
        showCheckedNodesButton = New Button

        Me.SuspendLayout()

        ' Initialize treeView1.
        treeView1.Location = New Point(0, 25)
        treeView1.Size = New Size(292, 248)
        treeView1.Anchor = AnchorStyles.Top Or AnchorStyles.Left Or AnchorStyles.Bottom Or AnchorStyles.Right
        treeView1.CheckBoxes = True

        ' Add nodes to treeView1.
        Dim node As TreeNode
        Dim x As Integer
        For x = 0 To 3
            ' Add a root node.
            node = treeView1.Nodes.Add(String.Format("Node{0}", x * 4))
            Dim y As Integer
            For y = 1 To 4
                ' Add a node as a child of the previously added node.
                node = node.Nodes.Add(String.Format("Node{0}", x * 4 + y))
            Next y
        Next x

        ' Set the checked state of one of the nodes to
        ' demonstrate the showCheckedNodesButton button behavior.
        treeView1.Nodes(1).Nodes(0).Nodes(0).Checked = True

        ' Initialize showCheckedNodesButton.
        showCheckedNodesButton.Size = New Size(144, 24)
        showCheckedNodesButton.Text = "Show Checked Nodes"
        AddHandler showCheckedNodesButton.Click, AddressOf showCheckedNodesButton_Click

        ' Initialize the form.
        Me.ClientSize = New Size(292, 273)
        Me.Controls.AddRange(New Control() {showCheckedNodesButton, treeView1})

        Me.ResumeLayout(False)
    End Sub

    <STAThreadAttribute()> _
    Shared Sub Main()
        Application.Run(New Form1)
    End Sub

    Private Sub showCheckedNodesButton_Click(ByVal sender As Object, ByVal e As EventArgs)
        ' Disable redrawing of treeView1 to prevent flickering 
        ' while changes are made.
        treeView1.BeginUpdate()

        ' Collapse all nodes of treeView1.
        treeView1.CollapseAll()

        ' Add the CheckForCheckedChildren event handler to the BeforeExpand event.
        AddHandler treeView1.BeforeExpand, AddressOf CheckForCheckedChildren

        ' Expand all nodes of treeView1. Nodes without checked children are 
        ' prevented from expanding by the checkForCheckedChildren event handler.
        treeView1.ExpandAll()

        ' Remove the checkForCheckedChildren event handler from the BeforeExpand 
        ' event so manual node expansion will work correctly.
        RemoveHandler treeView1.BeforeExpand, AddressOf CheckForCheckedChildren

        ' Enable redrawing of treeView1.
        treeView1.EndUpdate()
    End Sub

    ' Prevent expansion of a node that does not have any checked child nodes.
    Private Sub CheckForCheckedChildren(ByVal sender As Object, ByVal e As TreeViewCancelEventArgs)
        If Not HasCheckedChildNodes(e.Node) Then
            e.Cancel = True
        End If
    End Sub

    ' Returns a value indicating whether the specified 
    ' TreeNode has checked child nodes.
    Private Function HasCheckedChildNodes(ByVal node As TreeNode) As Boolean
        If node.Nodes.Count = 0 Then
            Return False
        End If
        Dim childNode As TreeNode
        For Each childNode In node.Nodes
            If childNode.Checked Then
                Return True
            End If
            ' Recursively check the children of the current child node.
            If HasCheckedChildNodes(childNode) Then
                Return True
            End If
        Next childNode
        Return False
    End Function 'HasCheckedChildNodes

End Class

' 导入命名空间
Imports System.Drawing
Imports System.Drawing.Drawing2D
Imports System.Windows.Forms

public class TreeViewSelectionCheckBoxes
   public Shared Sub Main
        Application.Run(New Form1)
   End Sub
End class

Public Class Form1
    Inherits System.Windows.Forms.Form

#Region " Windows Form Designer generated code "

    Public Sub New()
        MyBase.New()

        'This call is required by the Windows Form Designer.
        InitializeComponent()

        'Add any initialization after the InitializeComponent() call

    End Sub

    'Form overrides dispose to clean up the component list.
    Protected Overloads Overrides Sub Dispose(ByVal disposing As Boolean)
        If disposing Then
            If Not (components Is Nothing) Then
                components.Dispose()
            End If
        End If
        MyBase.Dispose(disposing)
    End Sub

    'Required by the Windows Form Designer
    Private components As System.ComponentModel.IContainer

    'NOTE: The following procedure is required by the Windows Form Designer
    'It can be modified using the Windows Form Designer.  
    'Do not modify it using the code editor.
    Friend WithEvents TreeView1 As System.Windows.Forms.TreeView
    Friend WithEvents TextBox1 As System.Windows.Forms.TextBox
    Friend WithEvents Button1 As System.Windows.Forms.Button
    <System.Diagnostics.DebuggerStepThrough()> Private Sub InitializeComponent()
        Me.TreeView1 = New System.Windows.Forms.TreeView
        Me.TextBox1 = New System.Windows.Forms.TextBox
        Me.Button1 = New System.Windows.Forms.Button
        Me.SuspendLayout()
        '
        'TreeView1
        '
        Me.TreeView1.ImageIndex = -1
        Me.TreeView1.Location = New System.Drawing.Point(88, 64)
        Me.TreeView1.Name = "TreeView1"
        Me.TreeView1.Nodes.AddRange(New System.Windows.Forms.TreeNode() {New System.Windows.Forms.TreeNode("Root", New System.Windows.Forms.TreeNode() {New System.Windows.Forms.TreeNode("Node 1", New System.Windows.Forms.TreeNode() {New System.Windows.Forms.TreeNode("Node 2"), New System.Windows.Forms.TreeNode("Node 3")}), New System.Windows.Forms.TreeNode("Node 4", New System.Windows.Forms.TreeNode() {New System.Windows.Forms.TreeNode("Node 5"), New System.Windows.Forms.TreeNode("Node 6")})})})
        Me.TreeView1.SelectedImageIndex = -1
        Me.TreeView1.Size = New System.Drawing.Size(121, 120)
        Me.TreeView1.TabIndex = 0
        '
        'TextBox1
        '
        Me.TextBox1.Location = New System.Drawing.Point(88, 200)
        Me.TextBox1.Name = "TextBox1"
        Me.TextBox1.Size = New System.Drawing.Size(120, 20)
        Me.TextBox1.TabIndex = 1
        Me.TextBox1.Text = ""
        '
        'Button1
        '
        Me.Button1.Location = New System.Drawing.Point(88, 232)
        Me.Button1.Name = "Button1"
        Me.Button1.Size = New System.Drawing.Size(120, 23)
        Me.Button1.TabIndex = 3
        Me.Button1.Text = "Show Check Boxes"
        '
        'Form1
        '
        Me.AutoScaleBaseSize = New System.Drawing.Size(5, 13)
        Me.ClientSize = New System.Drawing.Size(292, 273)
        Me.Controls.Add(Me.Button1)
        Me.Controls.Add(Me.TextBox1)
        Me.Controls.Add(Me.TreeView1)
        Me.Name = "Form1"
        Me.Text = "Form1"
        Me.ResumeLayout(False)

    End Sub

#End Region

    Private Sub TreeView1_AfterSelect(ByVal sender As System.Object, ByVal e As System.Windows.Forms.TreeViewEventArgs) Handles TreeView1.AfterSelect
        TextBox1.Text = e.Node.Text & " was selected."
    End Sub

    Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click
        TreeView1.CheckBoxes = True
    End Sub

    Private Sub TreeView1_AfterCheck(ByVal sender As Object, ByVal e As System.Windows.Forms.TreeViewEventArgs) Handles TreeView1.AfterCheck
        If e.Node.Checked Then
            TextBox1.Text = e.Node.Text & " is checked."
        Else
            TextBox1.Text = e.Node.Text & " is not checked."
        End If
    End Sub
End Class