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Drag & Drop...

My first time using TreeViews. I have TreeView1 set up to display my
directory structure just like Windows Explorer. I can drag & drop files and
folders over to TreeView2. I can re-arrange the structure in TreeView2
(putting files in different folders and such...like you do when you create a
structure for burning a CD).

I have two questions.

1. How can I remember the full path from TreeView1 (when it comes time to
actually do something with the arrangement in TreeView2)?
2. I have not been able to figure out how to get the DragOver part to work
correctly. In the code below, when I drag over a file node, it's supposed
to display the "not here" cursor. When I drag over a directory node (or the
root), it's supposed to display the "drop" cursor. It does fine except when
I drag over a file node and then drag off the file node. When I drag over
the file node, the cursor changes to "not here". When I drag off the file
node, I get an exception "object reference not set to an instance, try using
the NEW keyword". Looking for help to correct this.

Thanks.
Public Sub TreeViewISO_Dra gOver(ByVal sender As System.Object, ByVal e As
DragEventArgs) Handles TreeViewISO.Dra gOver
'Check that there is a TreeNode being dragged
If e.Data.GetDataP resent("System. Windows.Forms.T reeNode", True) = False Then
Exit Sub
'Get the TreeView raising the event (incase multiple on form)
Dim selectedTreevie w As TreeView = CType(sender, TreeView)
'As the mouse moves over nodes, provide feedback to
'the user by highlighting the node that is the
'current drop target
Dim pt As Point = CType(sender, TreeView).Point ToClient(New Point(e.X, e.Y))
Dim targetNode As TreeNode = selectedTreevie w.GetNodeAt(pt)
'See if the targetNode is currently selected,
'if so no need to validate again
If Not (selectedTreevi ew.SelectedNode Is targetNode) Then
'Select the node currently under the cursor
selectedTreevie w.SelectedNode = targetNode
'Check that the selected node is not the dropNode and
'also that it is not a child of the dropNode and
'therefore an invalid target
Dim dropNode As TreeNode =
CType(e.Data.Ge tData("System.W indows.Forms.Tr eeNode"), TreeNode)
If targetNode.Imag eIndex = 2 Then <== Exception thrown here...
e.Effect = DragDropEffects .None
Else
'Currently selected node is a suitable target
e.Effect = DragDropEffects .Move
End If
End If
End Sub
Nov 21 '05 #1
1 2299

1. Im not sure what your asking here. If you just want a path then why cant
you store it in a string? If you want the tree list structure then just
clone the node thats interests you (or its root) and store a reference to
this node in a variable.

2. If Not (selectedTreevi ew.SelectedNode Is targetNode)

If target node is Nothing then the code in the conditional still executes.
You then try to access a property of Nothing which is why the excepion gets
thrown.

targetNode.Imag eIndex

I would chnage the conditional too

If Not targetNot Is Nothing AndAlso (selectedTreevi ew.SelectedNode Is
targetNode) then

RR

"Terry Olsen" <to******@hotma il.com> wrote in message
news:OY******** ******@TK2MSFTN GP14.phx.gbl...
My first time using TreeViews. I have TreeView1 set up to display my
directory structure just like Windows Explorer. I can drag & drop files and folders over to TreeView2. I can re-arrange the structure in TreeView2
(putting files in different folders and such...like you do when you create a structure for burning a CD).

I have two questions.

1. How can I remember the full path from TreeView1 (when it comes time to
actually do something with the arrangement in TreeView2)?
2. I have not been able to figure out how to get the DragOver part to work
correctly. In the code below, when I drag over a file node, it's supposed
to display the "not here" cursor. When I drag over a directory node (or the root), it's supposed to display the "drop" cursor. It does fine except when I drag over a file node and then drag off the file node. When I drag over
the file node, the cursor changes to "not here". When I drag off the file
node, I get an exception "object reference not set to an instance, try using the NEW keyword". Looking for help to correct this.

Thanks.
Public Sub TreeViewISO_Dra gOver(ByVal sender As System.Object, ByVal e As
DragEventArgs) Handles TreeViewISO.Dra gOver
'Check that there is a TreeNode being dragged
If e.Data.GetDataP resent("System. Windows.Forms.T reeNode", True) = False Then Exit Sub
'Get the TreeView raising the event (incase multiple on form)
Dim selectedTreevie w As TreeView = CType(sender, TreeView)
'As the mouse moves over nodes, provide feedback to
'the user by highlighting the node that is the
'current drop target
Dim pt As Point = CType(sender, TreeView).Point ToClient(New Point(e.X, e.Y)) Dim targetNode As TreeNode = selectedTreevie w.GetNodeAt(pt)
'See if the targetNode is currently selected,
'if so no need to validate again
If Not (selectedTreevi ew.SelectedNode Is targetNode) Then
'Select the node currently under the cursor
selectedTreevie w.SelectedNode = targetNode
'Check that the selected node is not the dropNode and
'also that it is not a child of the dropNode and
'therefore an invalid target
Dim dropNode As TreeNode =
CType(e.Data.Ge tData("System.W indows.Forms.Tr eeNode"), TreeNode)
If targetNode.Imag eIndex = 2 Then <== Exception thrown here...
e.Effect = DragDropEffects .None
Else
'Currently selected node is a suitable target
e.Effect = DragDropEffects .Move
End If
End If
End Sub

Nov 21 '05 #2

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