当前位置: 首页>>代码示例>>VB.NET>>正文


VB.NET TreeView.BeforeExpand事件代码示例

本文整理汇总了VB.NET中System.Windows.Forms.TreeView.BeforeExpand事件的典型用法代码示例。如果您正苦于以下问题:VB.NET TreeView.BeforeExpand事件的具体用法?VB.NET TreeView.BeforeExpand怎么用?VB.NET TreeView.BeforeExpand使用的例子?那么恭喜您, 这里精选的事件代码示例或许可以为您提供帮助。您也可以进一步了解该事件所在System.Windows.Forms.TreeView的用法示例。


在下文中一共展示了TreeView.BeforeExpand事件的1个代码示例,这些例子默认根据受欢迎程度排序。您可以为喜欢或者感觉有用的代码点赞,您的评价将有助于系统推荐出更棒的VB.NET代码示例。

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.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

' 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

' 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
开发者ID:VB.NET开发者,项目名称:System.Windows.Forms,代码行数:48,代码来源:TreeView.BeforeExpand


注:本文中的System.Windows.Forms.TreeView.BeforeExpand事件示例由纯净天空整理自Github/MSDocs等开源代码及文档管理平台,相关代码片段筛选自各路编程大神贡献的开源项目,源码版权归原作者所有,传播和使用请参考对应项目的License;未经允许,请勿转载。