TreeView.TopNode 属性
获取树视图控件中第一个完全可见的树节点。
**命名空间:**System.Windows.Forms
**程序集:**System.Windows.Forms（在 system.windows.forms.dll 中）
语法
声明
Public Property TopNode As TreeNode
用法
Dim instance As TreeView
Dim value As TreeNode
value = instance.TopNode
instance.TopNode = value
public TreeNode TopNode { get; set; }
public:
property TreeNode^ TopNode {
TreeNode^ get ();
void set (TreeNode^ value);
}
/** @property */
public TreeNode get_TopNode ()
/** @property */
public void set_TopNode (TreeNode value)
public function get TopNode () : TreeNode
public function set TopNode (value : TreeNode)
属性值
TreeNode，表示树视图控件中第一个完全可见的树节点。
备注
最初，TopNode 将返回第一个根树节点，它位于 TreeView 的顶部。但是，如果用户已滚动查看内容，则可能会有另一个树节点位于顶部。
提示
当 Scrollable 属性值为 false 时，设置此属性不起任何作用。
示例
下面的代码示例演示如何使用 BeforeLabelEditAfterSelect 和 TopNode 成员。若要运行该示例，请将以下代码粘贴到一个包含名为 TreeView1 的 TreeView 控件的窗体中。从窗体的构造函数或 Load 方法调用 InitializeTreeView 方法。
Private Sub InitializeTreeView()
' Construct the TreeView object.
Me.TreeView1 = New System.Windows.Forms.TreeView
' Set dock, location, size name, and tab order
' values for the TreeView object.
With TreeView1
.Dock = System.Windows.Forms.DockStyle.Left
.Location = New System.Drawing.Point(0, 0)
.Name = "TreeView1"
.Size = New System.Drawing.Size(152, 266)
.TabIndex = 1
End With
' Set the LabelEdit property to true to allow the
' user to edit the TreeNode text.
Me.TreeView1.LabelEdit = True
' Declare and create objects needed to populate
' the TreeView.
Dim file, files(), filePath As String
files = New String() {"bigPresentation.ppt", "myFinances.xls", _
"myResume.doc"}
filePath = "c:\myFiles"
Dim nodes As New System.Collections.ArrayList
' Create a node for each file, setting the Text property to the
' file's name and the Tag property to file's fully-qualified name.
For Each file In files
Dim node As New TreeNode(file)
node.Tag = filePath & "\" & file
nodes.Add(node)
Next
' Create a new node named topNode and add the ArrayList of
' nodes to topNode.
Dim topNode As New TreeNode("myFiles", _
nodes.ToArray(GetType(TreeNode)))
topNode.Tag = filePath
' Add topNode to the TreeView.
TreeView1.Nodes.Add(topNode)
' Add the TreeView to the form.
Me.Controls.Add(TreeView1)
End Sub
Private Sub TreeView1_BeforeLabelEdit(ByVal sender As Object, _
ByVal e As NodeLabelEditEventArgs) Handles TreeView1.BeforeLabelEdit
' Determine whether the user has selected the top node. If so,
' change the LabelEdit property to false so the user cannot
' edit this label.
If (e.Node Is TreeView1.TopNode) Then
TreeView1.LabelEdit = False
MessageBox.Show("You are not allowed to edit the top node")
End If
' Set the LabelEdit property to true again.
TreeView1.LabelEdit = True
End Sub
...
' Handle the After_Select event.
Private Sub TreeView1_AfterSelect(ByVal sender As System.Object, _
ByVal e As System.Windows.Forms.TreeViewEventArgs) _
Handles TreeView1.AfterSelect
' Vary the response depending on which TreeViewAction
' triggered the event.
Select Case (e.Action)
Case TreeViewAction.ByKeyboard
MessageBox.Show("You like the keyboard!")
Case TreeViewAction.ByMouse
MessageBox.Show("You like the mouse!")
End Select
End Sub
private void InitializeTreeView()
{
// Construct the TreeView object.
this.TreeView1 = new System.Windows.Forms.TreeView();
// Set dock, location, size name, and tab order
// values for the TreeView object.
TreeView1.Dock = System.Windows.Forms.DockStyle.Left;
TreeView1.Location = new System.Drawing.Point(0, 0);
TreeView1.Name = "TreeView1";
TreeView1.Size = new System.Drawing.Size(152, 266);
TreeView1.TabIndex = 1;
// Associate the event-handling methods with the
// BeforeLabeEdit and the AfterSelect events.
TreeView1.BeforeLabelEdit +=
new NodeLabelEditEventHandler(TreeView1_BeforeLabelEdit);
TreeView1.AfterSelect +=
new TreeViewEventHandler(TreeView1_AfterSelect);
// Set the LabelEdit property to true to allow the
// user to edit the TreeNode text.
this.TreeView1.LabelEdit = true;
// Declare and create objects needed to populate
// the TreeView.
string[] files = new string[]{"bigPresentation.ppt",
"myFinances.xls", "myResume.doc"};;
string filePath = "c:\\myFiles";
System.Collections.ArrayList nodes =
new System.Collections.ArrayList();
// Create a node for each file, setting the Text property to the
// file's name and the Tag property to file's fully-qualified name.
foreach ( string file in files )
{
TreeNode node = new TreeNode(file);
node.Tag = filePath+"\\"+file;
nodes.Add(node);
}
TreeNode[] treeNodes = new TreeNode[nodes.Count];
nodes.CopyTo(treeNodes);
// Create a new node named topNode and add the ArrayList of
// nodes to topNode.
TreeNode topNode = new TreeNode("myFiles", treeNodes);
topNode.Tag = filePath;
// Add topNode to the TreeView.
TreeView1.Nodes.Add(topNode);
// Add the TreeView to the form.
this.Controls.Add(TreeView1);
}
private void TreeView1_BeforeLabelEdit(object sender,
NodeLabelEditEventArgs e)
{
// Determine whether the user has selected the top node. If so,
// change the LabelEdit property to false so the user cannot
// edit this label.
if (e.Node == TreeView1.TopNode)
{
TreeView1.LabelEdit = false;
MessageBox.Show("You are not allowed to edit the top node");
}
// Set the LabelEdit property to true again.
TreeView1.LabelEdit = true;
}
...
// Handle the After_Select event.
private void TreeView1_AfterSelect(System.Object sender,
System.Windows.Forms.TreeViewEventArgs e)
{
// Vary the response depending on which TreeViewAction
// triggered the event.
switch((e.Action))
{
case TreeViewAction.ByKeyboard:
MessageBox.Show("You like the keyboard!");
break;
case TreeViewAction.ByMouse:
MessageBox.Show("You like the mouse!");
break;
}
}
private:
void InitializeTreeView()
{
// Construct the TreeView object.
this->TreeView1 = gcnew System::Windows::Forms::TreeView;
// Set dock, location, size name, and tab order
// values for the TreeView object.
TreeView1->Dock = System::Windows::Forms::DockStyle::Left;
TreeView1->Location = System::Drawing::Point( 0, 0 );
TreeView1->Name = "TreeView1";
TreeView1->Size = System::Drawing::Size( 152, 266 );
TreeView1->TabIndex = 1;
// Associate the event-handling methods with the
// BeforeLabeEdit and the AfterSelect events.
TreeView1->BeforeLabelEdit += gcnew NodeLabelEditEventHandler( this, &Form1::TreeView1_BeforeLabelEdit );
TreeView1->AfterSelect += gcnew TreeViewEventHandler( this, &Form1::TreeView1_AfterSelect );
// Set the LabelEdit property to true to allow the
// user to edit the TreeNode text.
this->TreeView1->LabelEdit = true;
// Declare and create objects needed to populate
// the TreeView.
array<String^>^files = {"bigPresentation.ppt","myFinances.xls","myResume.doc"};
;
String^ filePath = "c:\\myFiles";
System::Collections::ArrayList^ nodes = gcnew System::Collections::ArrayList;
// Create a node for each file, setting the Text property to the
// file's name and the Tag property to file's fully-qualified name.
System::Collections::IEnumerator^ myEnum = files->GetEnumerator();
while ( myEnum->MoveNext() )
{
String^ file = safe_cast<String^>(myEnum->Current);
TreeNode^ node = gcnew TreeNode( file );
node->Tag = String::Concat( filePath, "\\", file );
nodes->Add( node );
}
array<TreeNode^>^treeNodes = gcnew array<TreeNode^>(nodes->Count);
nodes->CopyTo( treeNodes );
// Create a new node named topNode and add the ArrayList of
// nodes to topNode.
TreeNode^ topNode = gcnew TreeNode( "myFiles",treeNodes );
topNode->Tag = filePath;
// Add topNode to the TreeView.
TreeView1->Nodes->Add( topNode );
// Add the TreeView to the form.
this->Controls->Add( TreeView1 );
}
void TreeView1_BeforeLabelEdit( Object^ /*sender*/, NodeLabelEditEventArgs^ e )
{
// Determine whether the user has selected the top node. If so,
// change the LabelEdit property to false so the user cannot
// edit this label.
if ( e->Node == TreeView1->TopNode )
{
TreeView1->LabelEdit = false;
MessageBox::Show( "You are not allowed to edit the top node" );
}
// Set the LabelEdit property to true again.
TreeView1->LabelEdit = true;
}
...
private:
// Handle the After_Select event.
void TreeView1_AfterSelect( System::Object^ /*sender*/, System::Windows::Forms::TreeViewEventArgs^ e )
{
// Vary the response depending on which TreeViewAction
// triggered the event.
switch ( (e->Action) )
{
case TreeViewAction::ByKeyboard:
MessageBox::Show( "You like the keyboard!" );
break;
case TreeViewAction::ByMouse:
MessageBox::Show( "You like the mouse!" );
break;
}
}
private void InitializeTreeView()
{
// Construct the TreeView object.
this.treeView1 = new System.Windows.Forms.TreeView();
// Set dock, location, size name, and tab order
// values for the TreeView object.
treeView1.set_Dock(System.Windows.Forms.DockStyle.Left);
treeView1.set_Location(new System.Drawing.Point(0, 0));
treeView1.set_Name("TreeView1");
treeView1.set_Size(new System.Drawing.Size(152, 266));
treeView1.set_TabIndex(1);
// Associate the event-handling methods with the
// BeforeLabeEdit and the AfterSelect events.
treeView1.add_BeforeLabelEdit(
new NodeLabelEditEventHandler(treeView1_BeforeLabelEdit));
treeView1.add_AfterSelect(new TreeViewEventHandler(
treeView1_AfterSelect));
// Set the LabelEdit property to true to allow the
// user to edit the TreeNode text.
this.treeView1.set_LabelEdit(true);
// Declare and create objects needed to populate
// the TreeView.
String files[] = new String[] { "bigPresentation.ppt", "myFinances.xls",
"myResume.doc" };
String filePath = "c:\\myFiles";
System.Collections.ArrayList nodes = new System.Collections.ArrayList();
// Create a node for each file, setting the Text property to the
// file's name and the Tag property to file's fully-qualified name.
for (int iCtr = 0; iCtr < files.length; iCtr++) {
String file = files[iCtr];
TreeNode node = new TreeNode(file);
node.set_Tag(filePath + "\\" + file);
nodes.Add(node);
}
TreeNode treeNodes[] = new TreeNode[nodes.get_Count()];
nodes.CopyTo(treeNodes);
// Create a new node named topNode and add the ArrayList of
// nodes to topNode.
TreeNode topNode = new TreeNode("myFiles", treeNodes);
topNode.set_Tag(filePath);
// Add topNode to the TreeView.
treeView1.get_Nodes().Add(topNode);
// Add the TreeView to the form.
this.get_Controls().Add(treeView1);
} //InitializeTreeView
private void treeView1_BeforeLabelEdit(Object sender,
NodeLabelEditEventArgs e)
{
// Determine whether the user has selected the top node. If so,
// change the LabelEdit property to false so the user cannot
// edit this label.
if (e.get_Node().Equals(treeView1.get_TopNode())) {
treeView1.set_LabelEdit(false);
MessageBox.Show("You are not allowed to edit the top node");
}
// Set the LabelEdit property to true again.
treeView1.set_LabelEdit(true);
} //treeView1_BeforeLabelEdit
...
// Handle the After_Select event.
private void treeView1_AfterSelect(Object sender,
System.Windows.Forms.TreeViewEventArgs e)
{
// Vary the response depending on which TreeViewAction
// triggered the event.
switch (e.get_Action()) {
case TreeViewAction.ByKeyboard:
MessageBox.Show("You like the keyboard!");
break;
case TreeViewAction.ByMouse:
MessageBox.Show("You like the mouse!");
break;
}
} //treeView1_AfterSelect
平台
Windows 98、Windows 2000 SP4、Windows CE、Windows Millennium Edition、Windows Mobile for Pocket PC、Windows Mobile for Smartphone、Windows Server 2003、Windows XP Media Center Edition、Windows XP Professional x64 Edition、Windows XP SP2、Windows XP Starter Edition
.NET Framework 并不是对每个平台的所有版本都提供支持。有关受支持版本的列表，请参见系统要求。
版本信息
.NET Framework
受以下版本支持：2.0、1.1、1.0
请参见
参考
TreeView 类
TreeView 成员
System.Windows.Forms 命名空间
TreeNode.IsVisible 属性