本文整理匯總了VB.NET中System.Windows.Forms.TreeView.BeforeCollapse事件的典型用法代碼示例。如果您正苦於以下問題：VB.NET TreeView.BeforeCollapse事件的具體用法？VB.NET TreeView.BeforeCollapse怎麽用？VB.NET TreeView.BeforeCollapse使用的例子？那麽, 這裏精選的事件代碼示例或許可以為您提供幫助。您也可以進一步了解該事件所在類System.Windows.Forms.TreeView的用法示例。
在下文中一共展示了TreeView.BeforeCollapse事件的1個代碼示例，這些例子默認根據受歡迎程度排序。您可以為喜歡或者感覺有用的代碼點讚，您的評價將有助於係統推薦出更棒的VB.NET代碼示例。
示例1: CheckForCheckedChildren
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.ExpandAll()
' Add the CheckForCheckedChildren event handler to the BeforeExpand event.
AddHandler treeView1.BeforeCollapse, AddressOf CheckForCheckedChildren
' Expand all nodes of treeView1. Nodes without checked children are
' prevented from expanding by the checkForCheckedChildren event handler.
treeView1.CollapseAll()
' Remove the checkForCheckedChildren event handler from the BeforeExpand
' event so manual node expansion will work correctly.
RemoveHandler treeView1.BeforeCollapse, AddressOf CheckForCheckedChildren
' Enable redrawing of treeView1.
treeView1.EndUpdate()
End Sub
' Prevent collapse of a node that has checked child nodes.
Private Sub CheckForCheckedChildren(ByVal sender As Object, ByVal e As TreeViewCancelEventArgs)
If 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