Why isn't there a SelectedNodeChanged event for Windows.Forms.TreeView?

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深忆病人
深忆病人 2020-12-10 10:04

The System.Web.UI.WebControls.TreeView class offers this event, but the Forms version of TreeView doesn\'t. What\'s the equivalent in the Forms world? I\'m using AfterSelect

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  •  慢半拍i
    慢半拍i (楼主)
    2020-12-10 10:33

    OK, this is an OOOLD question, but the problem really annoyed me. I made this little helper class -- it works for me.

    Public Class TreeViewSelectedNodeChangeEventHandler
    Public Event SelectedTreeNodeChanged(sender As Object, e As EventArgs)
    
    Private m_selectedNode As TreeNode
    Private WithEvents m_tvw As TreeView
    
    Public Shared Function FromTree(tree As TreeView) As TreeViewSelectedNodeChangeEventHandler
        If Not IsNothing(tree) Then
            Return New TreeViewSelectedNodeChangeEventHandler(tree)
        End If
        Return Nothing
    End Function
    
    ''' Assigns 'Value' to 'this' and returns 'Value'.
    Private Function InLineAssign(Of V)(ByRef this As V, value As V) As V
        Dim ret = value
        this = value
        Return ret
    End Function
    

    May add other triggers, e.g. Control.Enter, MouseUp etc. etc.

    Private Sub keyUp(sender As Object, e As KeyEventArgs) Handles m_tvw.KeyUp
        If Not Me.m_selectedNode Is InLineAssign(Me.m_selectedNode, m_tvw.SelectedNode)  
    

    Then

        RaiseEvent SelectedTreeNodeChanged(m_tvw, EventArgs.Empty)
            End If
        End Sub
        Private Sub New(tv As TreeView)
            m_tvw = tv
        End Sub
    End Class
    

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