You can provide a combo box that has a drop-down list with the AjaxComboBoxCellType class.
This cell type is dependent on the combo extender of the Microsoft ASP.NET AJAX Control Toolkit. The appearance and behavior of this cell type is controlled by the AJAX Control Toolkit. For more information, see the Microsoft AJAX site. This celltype requires version 3.0.3.512 or later of the Ajax Toolkit.
All controls in the AJAX Control Toolkit can add or attach client behaviors to a target control. The target control is exposed as the Editor property of the extender cell type in Spread.
Unlike the other cell types in Spread, there are no restrictions and validation of any of the Extenders properties, so use this cell type carefully and provide validation as needed.
For a list of limitations with this AJAX cell type, refer to Working with ASP.NET AJAX Extender Cell Types.
For details on the properties and methods for this cell type, refer to the AjaxComboBoxCellType class.