How to drag and drop a datagridviewrow onto a treeview

[Nitesh]

Hi Guys,

I want to make u user control that contains a treeview. I will dynamically generate them on the form according to an option selected on a combobox. Then I have two datagridviews. One contains Categories(ID, Name) and the other contains Subcategories(ID,Name,CategoryID).

When I drag a row from gridview 1 it must add a node with that category name to the treeview.
When I drag a row from gridview2(subcategory) it must add a child node to the parent node it has been dropped on.

Please help me get going.

[jmcilhinney]

Do you already know the basics of drag & drop or are you starting from scratch?

[Nitesh]

hi JM,

I've got the basics down. I set the allowdrop property to true for both controls. Here is the treeview usercontrol code

Private Sub TreeView1_DragDrop(sender As Object, e As DragEventArgs) Handles TreeView1.DragDrop
        Dim row As DataRow = TryCast(e.Data.GetData(GetType(DataRow)), DataRow)
        If row IsNot Nothing Then
            Dim pt As Point

            pt = TreeView1.PointToClient(New Point(e.X, e.Y))

            Dim DestinationNode As TreeNode
            ' Get a handle to the node the source node was dragged onto

            DestinationNode = TreeView1.GetNodeAt(pt)

            If Not DestinationNode Is Nothing Then
                TreeView1.Nodes.Add(row.Field(Of Integer)("ID").ToString, row.Field(Of String)("Name"))
            End If

            'Dim hi As TreeListHitInfo = TreeList1.CalcHitInfo(TreeList1.PointToClient(New Point(e.X, e.Y)))
            ''If hi Is Nothing Then
            ''    Return
            ''End If
            'TreeView1. .AppendNode(row, hi.Node)
        End If
    End Sub


    Private Sub TreeView1_DragEnter(sender As Object, e As DragEventArgs) Handles TreeView1.DragEnter
        e.Effect = DragDropEffects.Copy
    End Sub

here is the gridview code:

Private Sub gcCategory_MouseDown(sender As Object, e As MouseEventArgs) Handles gcCategory.MouseDown
        hitInfo = GridView1.CalcHitInfo(New Point(e.X, e.Y))
    End Sub

    Private Sub gcCategory_MouseMove(sender As Object, e As MouseEventArgs) Handles gcCategory.MouseMove
        If hitInfo Is Nothing Then
            Return
        End If
        If e.Button <> MouseButtons.Left Then
            Return
        End If
        Dim dragRect As Rectangle = _
            New Rectangle(New Point(hitInfo.HitPoint.X - SystemInformation.DragSize.Width / 2, _
            hitInfo.HitPoint.Y - SystemInformation.DragSize.Height / 2), SystemInformation.DragSize)
        If (Not dragRect.Contains(New Point(e.X, e.Y))) Then
            Dim data As DataRow = GridView1.GetDataRow(hitInfo.RowHandle)
            gcCategory.DoDragDrop(data, DragDropEffects.Copy)
        End If
    End Sub

I am able to drag and drop onto the treeview. Not sure if my code is the best. I'm stuck on adding sub nodes. Right now I can only add parent nodes

[jmcilhinney]

When you drop, you should first identify the source of the row being dropped. As you're passing a DataRow, you could test its Table property to see whether you should be creating a root node or a child node. If you need to create a child node then you need to determine which node you dropped on and then add to its Nodes collection rather than the tree's Nodes collection.

You should also be handling the DragOver event of the TreeView. If dropping the current row would result in a new root node then you should display the Copy effect no matter where the cursor is. If it would result in a child node then the cursor must be over a root node to display the copy effect, otherwise dropping is no valid. If the cursor is over a child node or no node at all then no effect should be displayed because dropping cannot create a new node.

[Nitesh]

thanks again. will let you know how I get along