Hi Sajin
Have you tried using EditingControlShowing event of the Datagridview?
if (e.Control is DataGridViewComboBoxEditingControl)
{
((ComboBox)e.Control).DropDownStyle = ComboBoxStyle.DropDown;
((ComboBox)e.Control).AutoCompleteSource = AutoCompleteSource.ListItems;
((ComboBox)e.Control).AutoCompleteMode = System.Windows.Forms.AutoCompleteMode.Suggest;
}
Hope this helps.