TreeView.CheckBoxes-Eigenschaft
Ruft einen Wert ab, der angibt, ob neben den Strukturknoten im Strukturansicht-Steuerelement Kontrollkästchen angezeigt werden, oder legt diesen fest.
Namespace: System.Windows.Forms
Assembly: System.Windows.Forms (in system.windows.forms.dll)
Syntax
'Declaration
Public Property CheckBoxes As Boolean
'Usage
Dim instance As TreeView
Dim value As Boolean
value = instance.CheckBoxes
instance.CheckBoxes = value
public bool CheckBoxes { get; set; }
public:
property bool CheckBoxes {
bool get ();
void set (bool value);
}
/** @property */
public boolean get_CheckBoxes ()
/** @property */
public void set_CheckBoxes (boolean value)
public function get CheckBoxes () : boolean
public function set CheckBoxes (value : boolean)
Eigenschaftenwert
true, wenn neben jedem Strukturknoten im Strukturansicht-Steuerelement ein Kontrollkästchen angezeigt wird, andernfalls false. Der Standardwert ist false.
Hinweise
Ein Kontrollkästchen wird jeweils links neben der Strukturknotenbezeichnung und, sofern vorhanden, dem Image des Strukturknotens angezeigt. Mit den Kontrollkästchen lassen sich mehrere Strukturknoten gleichzeitig auswählen.
Wenn die CheckBoxes-Eigenschaft einer TreeView auf true festgelegt und die StateImageList-Eigenschaft festgelegt sind, zeigt jeder TreeNode in der TreeView in aktiviertem bzw. deaktiviertem Zustand entsprechend das erste oder das zweite Bild aus der StateImageList an. Die angezeigten Bilder können davon jedoch in den folgenden Situationen abweichen: Wenn der SelectedImageIndex des Knotens nicht auf den Wert 0 (null) oder 1 festgelegt und die CheckBoxes-Eigenschaft der übergeordneten TreeView auf false festgelegt ist, wird der SelectedImageIndex nicht automatisch auf -1 zurückgesetzt, um anzuzeigen, dass er nicht festgelegt ist. In diesem Fall wird das Zustandsbild an der angegebenen Indexposition angezeigt. Wenn CheckBoxes wieder auf true festgelegt wird, steht das erste bzw. zweite Bild von StateImageList jeweils für einen aktivierten bzw. deaktivierten Zustand.
Hinweis
Wenn die CheckBoxes-Eigenschaft zur Laufzeit festgelegt wird, wird das TreeView-Handle neu erstellt (siehe Control.RecreateHandle), um die Darstellung des Steuerelements zu aktualisieren. Dadurch werden alle Strukturknoten mit Ausnahme des ausgewählten TreeNode reduziert.
Beispiel
Im folgenden Codebeispiel wird das Ändern des Zustands einer TreeView veranschaulicht, um alle aktivierten Knoten anzuzeigen. Zu Beginn sind alle Knoten reduziert, und für das BeforeExpand-Ereignis wird ein Handler hinzugefügt. Anschließend werden alle Knoten erweitert. Der BeforeExpand-Ereignishandler bestimmt, ob ein bestimmter Knoten über aktivierte untergeordnete Knoten verfügt. Wenn ein Knoten über keine aktivierten untergeordneten Knoten verfügt, wird die Erweiterung an dem Knoten beendet. Damit Knoten wieder standardmäßig über Klicken auf das Pluszeichen neben dem Knoten erweitert werden können, wird der BeforeExpand-Ereignishandler anschließend entfernt.
Dieses Verhalten können Sie auch durch Behandeln des BeforeCollapse-Ereignisses implementieren. Das entsprechende Vorgehen wird im Beispiel zu dem Thema veranschaulicht.
Imports System
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 'New
<STAThreadAttribute()> _
Shared Sub Main()
Application.Run(New Form1)
End Sub 'Main
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 'showCheckedNodesButton_Click
' 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 'CheckForCheckedChildren
' 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 'Form1
using System;
using System.Drawing;
using System.Windows.Forms;
public class Form1 : Form
{
private TreeView treeView1;
private Button showCheckedNodesButton;
private TreeViewCancelEventHandler checkForCheckedChildren;
public Form1()
{
treeView1 = new TreeView();
showCheckedNodesButton = new Button();
checkForCheckedChildren =
new TreeViewCancelEventHandler(CheckForCheckedChildrenHandler);
this.SuspendLayout();
// Initialize treeView1.
treeView1.Location = new Point(0, 25);
treeView1.Size = new Size(292, 248);
treeView1.Anchor = AnchorStyles.Top | AnchorStyles.Left |
AnchorStyles.Bottom | AnchorStyles.Right;
treeView1.CheckBoxes = true;
// Add nodes to treeView1.
TreeNode node;
for (int x = 0; x < 3; ++x)
{
// Add a root node.
node = treeView1.Nodes.Add(String.Format("Node{0}", x*4));
for (int y = 1; y < 4; ++y)
{
// Add a node as a child of the previously added node.
node = node.Nodes.Add(String.Format("Node{0}", x*4 + y));
}
}
// 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";
showCheckedNodesButton.Click +=
new EventHandler(showCheckedNodesButton_Click);
// Initialize the form.
this.ClientSize = new Size(292, 273);
this.Controls.AddRange(new Control[]
{ showCheckedNodesButton, treeView1 } );
this.ResumeLayout(false);
}
[STAThreadAttribute()]
static void Main()
{
Application.Run(new Form1());
}
private void showCheckedNodesButton_Click(object sender, EventArgs e)
{
// 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.
treeView1.BeforeExpand += 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.
treeView1.BeforeExpand -= checkForCheckedChildren;
// Enable redrawing of treeView1.
treeView1.EndUpdate();
}
// Prevent expansion of a node that does not have any checked child nodes.
private void CheckForCheckedChildrenHandler(object sender,
TreeViewCancelEventArgs e)
{
if (!HasCheckedChildNodes(e.Node)) e.Cancel = true;
}
// Returns a value indicating whether the specified
// TreeNode has checked child nodes.
private bool HasCheckedChildNodes(TreeNode node)
{
if (node.Nodes.Count == 0) return false;
foreach (TreeNode childNode in node.Nodes)
{
if (childNode.Checked) return true;
// Recursively check the children of the current child node.
if (HasCheckedChildNodes(childNode)) return true;
}
return false;
}
}
#using <System.dll>
#using <System.Windows.Forms.dll>
#using <System.Drawing.dll>
using namespace System;
using namespace System::Drawing;
using namespace System::Windows::Forms;
public ref class Form1: public Form
{
private:
TreeView^ treeView1;
Button^ showCheckedNodesButton;
TreeViewCancelEventHandler^ checkForCheckedChildren;
public:
Form1()
{
treeView1 = gcnew TreeView;
showCheckedNodesButton = gcnew Button;
checkForCheckedChildren = gcnew TreeViewCancelEventHandler( this, &Form1::CheckForCheckedChildrenHandler );
this->SuspendLayout();
// Initialize treeView1.
treeView1->Location = Point(0,25);
treeView1->Size = System::Drawing::Size( 292, 248 );
treeView1->Anchor = static_cast<AnchorStyles>(AnchorStyles::Top | AnchorStyles::Left | AnchorStyles::Bottom | AnchorStyles::Right);
treeView1->CheckBoxes = true;
// Add nodes to treeView1.
TreeNode^ node;
for ( int x = 0; x < 3; ++x )
{
// Add a root node.
node = treeView1->Nodes->Add( String::Format( "Node{0}", x * 4 ) );
for ( int y = 1; y < 4; ++y )
{
// Add a node as a child of the previously added node.
node = node->Nodes->Add( String::Format( "Node{0}", x * 4 + y ) );
}
}
// 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 = System::Drawing::Size( 144, 24 );
showCheckedNodesButton->Text = "Show Checked Nodes";
showCheckedNodesButton->Click += gcnew EventHandler( this, &Form1::showCheckedNodesButton_Click );
// Initialize the form.
this->ClientSize = System::Drawing::Size( 292, 273 );
array<Control^>^temp0 = {showCheckedNodesButton,treeView1};
this->Controls->AddRange( temp0 );
this->ResumeLayout( false );
}
private:
void showCheckedNodesButton_Click( Object^ /*sender*/, EventArgs^ /*e*/ )
{
// 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.
treeView1->BeforeExpand += 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.
treeView1->BeforeExpand -= checkForCheckedChildren;
// Enable redrawing of treeView1.
treeView1->EndUpdate();
}
// Prevent expansion of a node that does not have any checked child nodes.
void CheckForCheckedChildrenHandler( Object^ /*sender*/, TreeViewCancelEventArgs^ e )
{
if ( !HasCheckedChildNodes( e->Node ) )
e->Cancel = true;
}
// Returns a value indicating whether the specified
// TreeNode has checked child nodes.
bool HasCheckedChildNodes( TreeNode^ node )
{
if ( node->Nodes->Count == 0 )
return false;
System::Collections::IEnumerator^ myEnum = node->Nodes->GetEnumerator();
while ( myEnum->MoveNext() )
{
TreeNode^ childNode = safe_cast<TreeNode^>(myEnum->Current);
if ( childNode->Checked )
return true;
// Recursively check the children of the current child node.
if ( HasCheckedChildNodes( childNode ) )
return true;
}
return false;
}
};
int main()
{
Application::Run( gcnew Form1 );
}
import System.*;
import System.Drawing.*;
import System.Windows.Forms.*;
public class Form1 extends Form
{
private TreeView treeView1;
private Button showCheckedNodesButton;
private TreeViewCancelEventHandler checkForCheckedChildren;
public Form1()
{
treeView1 = new TreeView();
showCheckedNodesButton = new Button();
checkForCheckedChildren =
new TreeViewCancelEventHandler(CheckForCheckedChildrenHandler);
this.SuspendLayout();
// Initialize treeView1.
treeView1.set_Location(new Point(0, 25));
treeView1.set_Size(new Size(292, 248));
treeView1.set_Anchor(AnchorStyles.Top | AnchorStyles.Left
| AnchorStyles.Bottom | AnchorStyles.Right);
treeView1.set_CheckBoxes(true);
// Add nodes to treeView1.
TreeNode node;
for (int x = 0; x < 3; ++x) {
// Add a root node.
node = treeView1.get_Nodes().Add(String.Format
("Node{0}", (Int32)(x * 4)));
for (int y = 1; y < 4; ++y) {
// Add a node as a child of the previously added node.
node = node.get_Nodes().Add(String.Format
("Node{0}", (Int32)(x * 4 + y)));
}
}
// Set the checked state of one of the nodes to
// demonstrate the showCheckedNodesButton button behavior.
treeView1.get_Nodes().get_Item(1).get_Nodes().get_Item(0).
get_Nodes().get_Item(0).set_Checked(true);
// Initialize showCheckedNodesButton.
showCheckedNodesButton.set_Size(new Size(144, 24));
showCheckedNodesButton.set_Text("Show Checked Nodes");
showCheckedNodesButton.add_Click(
new EventHandler(showCheckedNodesButton_Click));
// Initialize the form.
this.set_ClientSize(new Size(292, 273));
this.get_Controls().AddRange(new Control[]
{ showCheckedNodesButton, treeView1 });
this.ResumeLayout(false);
} //Form1
public static void main(String[] args)
{
Application.Run(new Form1());
} //main
private void showCheckedNodesButton_Click(Object sender, EventArgs e)
{
// 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.
treeView1.add_BeforeExpand(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.
treeView1.remove_BeforeExpand(checkForCheckedChildren);
// Enable redrawing of treeView1.
treeView1.EndUpdate();
} //showCheckedNodesButton_Click
// Prevent expansion of a node that does not have any checked child nodes.
private void CheckForCheckedChildrenHandler(Object sender,
TreeViewCancelEventArgs e)
{
if (!(HasCheckedChildNodes(e.get_Node()))) {
e.set_Cancel(true);
}
} //CheckForCheckedChildrenHandler
// Returns a value indicating whether the specified
// TreeNode has checked child nodes.
private boolean HasCheckedChildNodes(TreeNode node)
{
if (node.get_Nodes().get_Count() == 0) {
return false;
}
for (int iCtr = 0; iCtr < node.get_Nodes().get_Count(); iCtr++) {
TreeNode childNode = node.get_Nodes().get_Item(iCtr);
if (childNode.get_Checked()) {
return true;
}
// Recursively check the children of the current child node.
if (HasCheckedChildNodes(childNode)) {
return true;
}
}
return false;
} //HasCheckedChildNodes
} //Form1
Plattformen
Windows 98, Windows 2000 SP4, Windows CE, Windows Millennium Edition, Windows Mobile für Pocket PC, Windows Server 2003, Windows XP Media Center Edition, Windows XP Professional x64 Edition, Windows XP SP2, Windows XP Starter Edition
.NET Framework unterstützt nicht alle Versionen sämtlicher Plattformen. Eine Liste der unterstützten Versionen finden Sie unter Systemanforderungen.
Versionsinformationen
.NET Framework
Unterstützt in: 2.0, 1.1, 1.0
.NET Compact Framework
Unterstützt in: 2.0, 1.0
Siehe auch
Referenz
TreeView-Klasse
TreeView-Member
System.Windows.Forms-Namespace
TreeNode.Checked-Eigenschaft