Workaround:
private void radButton1_Click(object sender, EventArgs e)
{
    var allNodes = radTreeView1.TreeViewElement.GetNodes().ToList();

    int row = 0;
  
    Workbook workbook = new Workbook();
    Worksheet newWorksheet = workbook.Worksheets.Add();

    foreach (var item in allNodes)
    {

        CellSelection cell = newWorksheet.Cells[row, item.Level];
        cell.SetValue(item.Text);

        cell = newWorksheet.Cells[row++, 2];
        cell.SetValue(item.Checked);

    }

    var formatProvider = new XlsxFormatProvider();


    var bytes = formatProvider.Export(workbook);
    File.WriteAllBytes(@"D:\Test.xlsx", bytes);


}

To reproduce:

radTreeView1.Filter = "new";
var node = new RadTreeNode( "test" );
radTreeView1.Nodes.Add( node );
//here the node is not in the Nodes collection
if ( radTreeView1.Nodes.Contains( node ) == false )
{
 radTreeView1.Nodes.Add( new RadTreeNode( "test" ) );
}

Workaround: remove the filter, perform the desired check and restore the filter

Scenario: We have an object P which has two lists of child objects of types C1 and C2.
If we create a list of P and we try to bind the tree to this list and display the two lists as child nodes, we will not succeed.

Private Sub LoadTvObjectInApp()
 
        Dim objectInApps As IQueryable(Of ObjectInApp)
        objectInApps = _context.ObjectInApps.Where(Function(c) (c.ApplicatieCode = "zis") AndAlso Not (c.GroepNaam = "hulp" AndAlso c.IsSysteemObject = True))
        

Sort the selected nodes according to their position in the tree

RadTreeView. Add node templates as ASP.NET AJAX - http://www.telerik.com/help/aspnet-ajax/treeview-templates-structure.html

I need to drop a simple plain text from a textbox into a Rad Treeview.
I just read the forum, I'm mixing OLE Drag & Drop and RadTreeView Drag & Drop. The Events seems to be right and they seems to work fine.
But I'm just having a problem with the Visual Indicators of the treeview:

When I drag a regular node inside the treeview, I can see that visual indicators (the target node is highlighted, I can see a line of dots showing the direction above or below the target node, or the "forbidden" cursor, etc).
And when I actually try to drag a simple text inside the treeview, I don't see any of those stuff.
I need the same visual behavior when dropping a simple text. I need to see the indicators and I don't know how to activate them.