protected override void OnMouseDown(DataGridViewCellMouseEventArgs e) { base.OnMouseDown(e); if (!ReadOnly) { // Any mouse-click on the cell should be passed along to any // combo-box control. if (IsInEditMode) { DataGridViewComboBoxEditingControl cb = (DataGridView.EditingControl as DataGridViewComboBoxEditingControl); if (cb != null) { cb.OnMouseDownInternal(e); } } } }