ASP.Net Treeview check node exists

Question

I am working with ASP.Net Treeview and I need to check the existence of a node before adding a new node so that I don't have a duplication (which is what I am getting at the moment because of the state of the data.

I have tried TreeView1.FindNode(newNode.Text) which does get me a value if the nodes exists, but when trying to run a if statement on it to check its not nothing, or if it exists visual studio gives me an error to advise that cannot convert string to Boolean.

When trying

If Convert.ToBoolean(TreeView1.FindNode(node.Id)) = Nothing Then
                exists = False
            Else
                exists = True
End If

this always returns false even if it is not nothing

when trying

If TreeView1.FindNode(node.Id) = Nothing Then
                exists = False
            Else
                exists = True
End If`

this is where I get the error.

Any and all help would be very much appreciated.

thanks

I think this post describes a solution to your issue : stackoverflow.com/questions/6097029/… Hope it helps. — Marius B.
– Marius B., Commented Nov 19, 2015 at 15:15

Rahul Singh · Accepted Answer · 2015-11-19 16:54:38Z

2

The problem is TreeView1.FindNode returns TreeNode and you are trying to convert that to a boolean which will never work. This should work:-

If TreeView1.FindNode(node.Id) Is Nothing Then
      exists = False
Else
      exists = True
End If

Update:

You can also use a little bit of LINQ to find existance. I personally like this approach:-

Dim exist As Boolean = TreeView1.Nodes.OfType(Of TreeNode)() _
                                      .Any(Function(x) x.Value = node.Id)

edited Nov 19, 2015 at 16:54

answered Nov 19, 2015 at 15:18

Rahul Singh

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3 Comments

Simon Price Over a year ago

I realized this just before seeing your answer... anyone can feel free to mark me down for my utter stupidity

Rahul Singh Over a year ago

@SimonPrice - Hey its not stupidity, these things happens in coding world :) I have added one more approach by which we can find the existence of a treenode.

Simon Price Over a year ago

Thank you, I am able to find the parent with the initial attempt but I'm unable to find specific child nodes now so hopefully this new bit of code will help me too.

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