A root item is an item that has no parent (ItemParent() = 0). Use the RootItem property of the Items object to enumerates the root items. Use the AddItem to add root items to the control. Use the InsertItem method to insert child items.

The following VB sample enumerates all root items:

Dim i As Long, n As Long
With ComboBox1.Items
    n = .RootCount
    For i = 0 To n - 1
        Debug.Print .CellCaption(.RootItem(i), 0)
    Next
End With

The following C++ sample enumerates all root items:

#include "Items.h"
CItems items = m_combobox.GetItems();
for ( long i = 0 ; i < items.GetRootCount(); i++ )
{
	COleVariant vtItem( items.GetRootItem(i) ), vtColumn( long(0) );
	OutputDebugString( V2S( &items.GetCellCaption( vtItem, vtColumn ) ) );
}

The following VB.NET sample enumerates all root items:

With AxComboBox1.Items
    Dim i As Integer
    For i = 0 To .RootCount - 1
        Debug.Print(.CellCaption(.RootItem(i), 0))
    Next
End With

The following C# sample enumerates all root items:

for (int i = 0; i < axComboBox1.Items.RootCount; i++)
{
	object strCaption = axComboBox1.Items.get_CellCaption(axComboBox1.Items.get_RootItem(i), 0);
	System.Diagnostics.Debug.WriteLine(strCaption != null ? strCaption.ToString() : "");
}

The following VFP sample enumerates all root items:

with thisform.ComboBox1.Items
	local i
	for i = 0 to .RootCount - 1
		.DefaultItem = .RootItem(i)
		wait window nowait .CellCaption(0,0)
	next
endwith