If the cell is editable, this list of values is used to populate the drop-down System.Windows.Forms.ComboBox used to edit the cell. In this case, the order of the items in the combo list is determined by the order of the elements in the dictionary.

The most common dictionary class, System.Collections.Hashtable, uses arbitrary order. If you want control over the item order, use a different dictionary class such as System.Collections.Specialized.ListDictionary.

The C1FlexGrid assembly also includes a MultiColumnDictionary class, which can be used to create multi-column and data-bound dictionaries.

Reference

CellStyle Class
CellStyle Members