TreeView.BeforeCheck TreeView.BeforeCheck TreeView.BeforeCheck TreeView.BeforeCheck Event

定義

ツリー ノードのチェック ボックスがオンにされる前に発生します。Occurs before the tree node check box is checked.

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 

次のコード例のすべての子ツリー ノードの更新をTreeNodeにユーザーがチェック状態を変更します。The following code example updates all the child tree nodes of a TreeNode when the user changes its checked state. このコードが必要です、Formで、TreeViewを持つTreeNode内のオブジェクトそのTreeNodeCollectionThis code requires that you have a Form with a TreeView that has TreeNode objects in its TreeNodeCollection. TreeNodeCollection子ノードを持つツリー ノードを持つ必要があります。The TreeNodeCollection should have tree nodes with child nodes.

// 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 

注釈

注意

設定、TreeNode.Checked内からのプロパティ、BeforeCheckまたはAfterCheckイベントがイベントを複数回発生して、予期しない動作が発生することができます。Setting the TreeNode.Checked property from within the BeforeCheck or AfterCheck event causes the event to be raised multiple times and can result in unexpected behavior. たとえば、設定することがあります、Checkedしたら、ユーザーが展開し、それぞれを個別に確認する必要があるないようには、更新、子ノードを再帰的にイベント ハンドラーのプロパティ。For example, you might set the Checked property in the event handler when you are recursively updating the child nodes, so that the user does not have to expand and check each one individually. 場合のみ再帰的なコードを実行するイベント ハンドラーにロジックを追加、イベントが複数回発生していることを防ぐために、Actionのプロパティ、TreeViewEventArgsに設定されていないTreeViewAction.Unknownします。To prevent the event from being raised multiple times, add logic to your event handler that only executes your recursive code if the Action property of the TreeViewEventArgs is not set to TreeViewAction.Unknown.

イベントを処理する方法の詳細については、次を参照してください。処理とイベントの発生します。For more information about how to handle events, see Handling and Raising Events.

適用対象

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