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

Question

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

Answer 1

There's none in WinForms TreeView. To quote MSDN for TreeView.AfterSelect:

This event does not occur when the node is unselected. To detect this occurrence, handle the Control.MouseUp event and test the TreeNode.IsSelected property.

Yes, this sucks.

Answer 2

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

''' <summary>Assigns 'Value' to 'this' and returns 'Value'.</summary>
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

Answer 3

There's nothing wrong with using AfterSelect.

However, note that it won't fire if the selection is cleared (if SelectedNode becomes null) Instead, you can handle MouseUp, as recommended in the documentation.

Answer 4

There's none in WinForms TreeView. To quote MSDN for TreeView.AfterSelect:

This event does not occur when the node is unselected. To detect this occurrence, handle the Control.MouseUp event and test the TreeNode.IsSelected property.

You'd better use TreeView.NodeMouseClick event combined with AfterSelect. AfterSelect isn't called when you select the previously selected SelectedNode. So just call AfterSelect when necessary, e.Node helps you.

private void treeView1_NodeMouseClick(object sender, TreeNodeMouseClickEventArgs e)
    {
        if (e.Node == tv.SelectedNode)
            treeView1_AfterSelect(sender, null);
    }