How to detect if no node selected in TreeView

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Hi All.
I Am wondering how to detect if user doesn't chose the node on a tree view.
Because I get the Node name to do something like

dim id as string

id = TreeView1.SelectedNode.Name

it get error if user doesn't chose the node.

This function seem to have problem

SQL

Public Function NoNodeSelected(ByVal TView As TreeView)
    Dim nodes As TreeNodeCollection = TView.Nodes
    Dim n As TreeNode
    For Each n In nodes
        If n.IsSelected Then
            NoNodeSelected = False
        End If
    Next
    NoNodeSelected = True 'Không có node nào được chọn
    'Scroll through each Treeview Node

    'For i = 0 To TView.GetNodeCount(True) Step 1
    '    If TView.Nodes(i).IsSelected Then
    '        NoNodeSelected = False
    '    End If

    'Next
    'For Each Node As TreeNode In TView.Nodes
    '    If Node.IsSelected Then
    '        NoNodeSelected = False
    '    End If
    'Next
End Function

It only search the level 1.

Can anybody correct it?

Posted 20-Mar-13 22:13pm

hmanhha

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Maciej Los · Answer 1 · 2013-03-21T07:24:00

Solution 1

windows forms:
Use TreeView.SelectedNode[^] property, which get or set selected node for currently selected Treeview. If no TreeNode is currently selected, the SelectedNode property is a null reference (Nothing in Visual Basic).

To check it in code:

VB

Dim tvn As System.Windows.Forms.TreeNode = Me.TreeView1.SelectedNode
MsgBox("Is selected node: " & (Not tvn Is Nothing).ToString)

Posted 21-Mar-13 7:24am

Maciej Los

Comments

phil.o 21-Mar-13 13:51pm

5'd!

No need to iterate through the complete collection, which can be huge with TreeViews.
Smart and concise. Thanks ;)

Maciej Los 21-Mar-13 14:22pm

Thank you, phil.o ;)