Filter doesn't work anymore

Hello,

I’ve a Flegrid.
all works good.

I replace a Texbox’s column by a Combobox’s Column.
All is ok but my filter on this colum doesn’t work anymore.

this is my filter :

var f = new C1.Win.C1FlexGrid.ColumnFilter();
                var c1 = f.ConditionFilter.Condition1;
                c1.Operator = C1.Win.C1FlexGrid.ConditionOperator.Contains;
                c1.Parameter = this.cmbCategorie.Text;



                this.C1ListeAliment.Cols["CATEGORIE"].Filter = f;

this is my combobox :

private Hashtable ListCat = new Hashtable();
….
…
 C1ListeAliment.Cols["CATEGORIE"].DataMap = ListCat;
..
..
..
private void C1ListeAliment_AfterRowColChange(object sender, RangeEventArgs e)
        {
        
                this.GestionComboCategorie(C1ListeAliment[C1ListeAliment.Row, C1ListeAliment.Cols["CATEGORIE"].Index].ToString().Trim());
                            

        }
…
…
…
 private void GestionComboCategorie(string _CatEncours)
        {
            ListCat.Clear();
            
            switch (_CatEncours)
            {
                case "P":
                case "F":
                    ListCat.Add("P ", "P ");
                    ListCat.Add("F ", "F ");

                    break;
                case "JB":
                case "CA":
                case "CE":
                case "CP":
                    ListCat.Add("JB", "JB");
                    ListCat.Add("CA", "CA");
                    ListCat.Add("CE", "CE");
                    ListCat.Add("CP", "CP");
                    break;
                case "M":
                case "A":
                    ListCat.Add("M ", "M ");
                    ListCat.Add("A ", "A ");
                    break;
                case "U":
                case "SP":
                    ListCat.Add("U ", "U ");
                    ListCat.Add("SP", "SP");
                    break;

                default:
                    _CatEncours = _CatEncours.Length == 0 ? "  " : _CatEncours;
                    ListCat.Add(_CatEncours, _CatEncours);
                    break;
            }

               

        }

do you see any problem?
thk