An empty cell would be fine with me. How can I do it?

That depends. I assuming your tree is bound to a data source, and that you are showing a CheckBox in the cell by setting the Editor property of the column to a CheckEditor. If that's the case, you could change the editor on the child node cells to an image renderer.

        private EmbeddableImageRenderer embeddableImageRenderer = new EmbeddableImageRenderer();
        private void ultraTree1_InitializeDataNode(object sender, Infragistics.Win.UltraWinTree.InitializeDataNodeEventArgs e)
        {
            if (null != e.Node.Parent)
            {
                e.Node.Cells["Boolean 1"].Editor = embeddableImageRenderer;
            }
        }

This is kind've a hack. Basically, you are telling the cell to display as an image, and since the boolean value in the cell cannot be converted into an image, it shows a blank. It also makes it so the user cannot edit the cell, so it works pretty well.

If this doesn't work because one of my assumptions is wrong, then the next best thing would be to use a CreationFilter to prevent the cell from creating the CheckBox elements.

my tree is not bound. If I am not mistaken, the InitializeDataNode won't be triggered.

What would be the method for an unbound tree?

If the tree is not bound, then you must be adding each node to the tree in code.

So you could add the node and then set the Editor on the cell immediately after adding the node to the tree.

Another option would be to use a CreationFilter, which is a bit more code, but it might be a bit more efficient and also it will work for both a bound and unbound tree.

        private void Form1_Load(object sender, EventArgs e)
        {
            this.ultraTree1.CreationFilter = new NodeCheckboxCreationFilter();
        }

        public class NodeCheckboxCreationFilter : IUIElementCreationFilter
        {

            void IUIElementCreationFilter.AfterCreateChildElements(UIElement parent)
            {
                // Do nothing. 
            }

            bool IUIElementCreationFilter.BeforeCreateChildElements(UIElement parent)
            {

                UltraTreeNodeCellUIElement ultraTreeNodeCellUIElement = parent as UltraTreeNodeCellUIElement;
                if (null != ultraTreeNodeCellUIElement)
                {
                    UltraTreeNodeCell cell = ultraTreeNodeCellUIElement.GetContext(typeof(UltraTreeNodeCell)) as UltraTreeNodeCell;
                    if (null != cell)
                    {
                        if (cell.Column.Key == "Boolean 1" && cell.Node.Parent != null)
                        {
                            return true;
                        }
                    }
                }
                
                return false;   
            }
        }

It seems that it does the job! Thanks again

Hm, maybe those are leftover checkbox elements that are not getting removed. Right before you return true from the CreationFilter, add this:

parent.ChildElements.Clear();

Let me know if that doesn't help.

Any ideas why I sometimes see some ghost?

As shown on the attached image, only the purple line (level 0) should show a checkbox.

The ghosts appear here and there not always and the same place, sometimes after I do a ExpandAll, sometime when scrolling, ...

Hi

The CreationFilter does the trick. Thanks.

I just checked again and I don't have an editor. Here is my code (referencing v.12.2):

			//set the ColumnSet
			UltraTreeColumnSet rootColumnSet = treeHeaders.ColumnSettings.RootColumnSet;
 
			rootColumnSet.AllowCellEdit = AllowCellEdit.Full;
			
 
			_columnSelected = rootColumnSet.Columns.Add("Selected");
			_columnSelected.DataType = typeof (bool);
			_columnSelected.AllowCellEdit = AllowCellEdit.Full;
			_columnSelected.ButtonDisplayStyle = ButtonDisplayStyle.Always;

Really? If I don't assign a CheckEditor to the column, it displays as "true" or "false" on mine.

Anyway, no - it doesn't matter whether you use an editor or not.