public:
event System::Windows::Forms::TreeViewCancelEventHandler ^ BeforeCheck;
public event System.Windows.Forms.TreeViewCancelEventHandler BeforeCheck;
member this.BeforeCheck : System.Windows.Forms.TreeViewCancelEventHandler
Public Custom Event BeforeCheck As TreeViewCancelEventHandler
下列程式碼範例會在使用者變更其核取狀態時，更新 的所有子樹狀節點
TreeNode
。 此程式碼需要您具有
Form
TreeView
的 ，且其
TreeNodeCollection
中具有
TreeNode
物件。
TreeNodeCollection
應該有具有子節點的樹狀節點。
// Updates all child tree nodes recursively.
void CheckAllChildNodes( TreeNode^ treeNode, bool nodeChecked )
IEnumerator^ myEnum = treeNode->Nodes->GetEnumerator();
while ( myEnum->MoveNext() )
TreeNode^ node = safe_cast<TreeNode^>(myEnum->Current);
node->Checked = nodeChecked;
if ( node->Nodes->Count > 0 )
// If the current node has child nodes, call the CheckAllChildsNodes method recursively.
this->CheckAllChildNodes( node, nodeChecked );
// NOTE This code can be added to the BeforeCheck event handler instead of the AfterCheck event.
// After a tree node's Checked property is changed, all its child nodes are updated to the same value.
void node_AfterCheck( Object^ /*sender*/, TreeViewEventArgs^ e )
// The code only executes if the user caused the checked state to change.
if ( e->Action != TreeViewAction::Unknown )
if ( e->Node->Nodes->Count > 0 )
/* Calls the CheckAllChildNodes method, passing in the current
Checked value of the TreeNode whose checked state changed. */
this->CheckAllChildNodes( e->Node, e->Node->Checked );
// Updates all child tree nodes recursively.
private void CheckAllChildNodes(TreeNode treeNode, bool nodeChecked)
foreach(TreeNode node in treeNode.Nodes)
node.Checked = nodeChecked;
if(node.Nodes.Count > 0)
// If the current node has child nodes, call the CheckAllChildsNodes method recursively.
this.CheckAllChildNodes(node, nodeChecked);
// NOTE This code can be added to the BeforeCheck event handler instead of the AfterCheck event.
// After a tree node's Checked property is changed, all its child nodes are updated to the same value.
private void node_AfterCheck(object sender, TreeViewEventArgs e)
// The code only executes if the user caused the checked state to change.
if(e.Action != TreeViewAction.Unknown)
if(e.Node.Nodes.Count > 0)
/* Calls the CheckAllChildNodes method, passing in the current
Checked value of the TreeNode whose checked state changed. */
this.CheckAllChildNodes(e.Node, e.Node.Checked);
' Updates all child tree nodes recursively.
Private Sub CheckAllChildNodes(treeNode As TreeNode, nodeChecked As Boolean)
Dim node As TreeNode
For Each node In treeNode.Nodes
node.Checked = nodeChecked
If node.Nodes.Count > 0 Then
' If the current node has child nodes, call the CheckAllChildsNodes method recursively.
Me.CheckAllChildNodes(node, nodeChecked)
End If
Next node
End Sub
' NOTE This code can be added to the BeforeCheck event handler instead of the AfterCheck event.
' After a tree node's Checked property is changed, all its child nodes are updated to the same value.
Private Sub node_AfterCheck(sender As Object, e As TreeViewEventArgs) Handles treeView1.AfterCheck
' The code only executes if the user caused the checked state to change.
If e.Action <> TreeViewAction.Unknown Then
If e.Node.Nodes.Count > 0 Then
' Calls the CheckAllChildNodes method, passing in the current
' Checked value of the TreeNode whose checked state changed.
Me.CheckAllChildNodes(e.Node, e.Node.Checked)
End If
End If
End Sub
TreeNode.Checked
從 或
AfterCheck
事件中
BeforeCheck
設定 屬性會導致事件多次引發，而且可能會導致非預期的行為。 例如，當您遞迴更新子節點時，可能會在事件處理常式中設定
Checked
屬性，讓使用者不需要個別展開和檢查每個節點。 若要防止多次引發事件，請將邏輯新增至事件處理常式，只有在 的
TreeViewEventArgs
屬性未設定
TreeViewAction.Unknown
為 時
Action
，才會執行遞迴程式碼。
如需如何處理事件的詳細資訊，請參閱
處理和引發事件
。
