Are you setting e.Size? Setting this event arg property in CurrentCellShowingDropDown is normally how the dropdown width is controlled.
For ComboBoxes and GridListControl cells, you control the number of items displayed in the list by setting the DropDownRows property at some point (in CurrentCellShowingDropoDown is OK or you can do it in FormLoad if it is fixed grid-wide).
private void gridControl1_CurrentCellShowingDropDown(object sender, GridCurrentCellShowingDropDownEventArgs e)
{
GridCurrentCell cc = this.gridControl1.CurrentCell;
if(cc.ColIndex == 1 && cc.RowIndex == 23)
{
GridComboBoxCellRenderer cr = cc.Renderer as GridComboBoxCellRenderer;
if(cr != null)
{
((GridComboBoxListBoxPart)cr.ListBoxPart).DropDownRows = 3;
cr.ListBoxPart.BackColor = Color.Blue;
}
}
else if(cc.ColIndex == 1 && cc.RowIndex == 35)
{
GridDropDownGridListControlCellRenderer cr = cc.Renderer as GridDropDownGridListControlCellRenderer;
if(cr != null)
{
((GridDropDownGridListControlPart)cr.ListControlPart).DropDownRows = 3;
cr.ListControlPart.BackColor = Color.Blue;
cr.ListControlPart.ShowColumnHeader = false;
}
}
}