TFS ComboBox

using Microsoft.TeamFoundation.WorkItemTracking.Client;
using Microsoft.TeamFoundation.WorkItemTracking.Controls;
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Windows.Forms;

namespace MyTFSCustomFields
{
    public class TFSCombo: ComboBox, IWorkItemControl
    {
        public TFSCombo()
        {
            this.SelectedValueChanged += TFSCombo_SelectedValueChanged;

            // Simulation de la récupération des éléments :
            this.Items.Clear();
            this.Items.AddRange(new string[] { "1", "2", "3" });
        }

        void TFSCombo_SelectedValueChanged(object sender, EventArgs e)
        {
            // On enregistre dès la modification.
            this.FlushToDatasource();
        }

        #region Implementation Interface
        // Propriétés
        public event EventHandler AfterUpdateDatasource;

        public event EventHandler BeforeUpdateDatasource;

        public bool ReadOnly { get; set; }

        public object WorkItemDatasource { get; set; }

        public string WorkItemFieldName { get; set; }

        public System.Collections.Specialized.StringDictionary Properties { get; set; }

        // Méthodes
        public void Clear()
        {
            this.SelectedIndex = -1;
        }

        public void FlushToDatasource()
        {
            // Sauvegarde de la valeur vers le WI.
            if ((this.WorkItemDatasource as WorkItem) == null || (this.WorkItemDatasource as WorkItem).Fields[this.WorkItemFieldName] == null)
            {
//                this.Items.Add(string.Format("Either WI is null : '{0}'", this.WorkItemDatasource as WorkItem));
                return;
            }

            (WorkItemDatasource as WorkItem).Fields[WorkItemFieldName].Value = this.SelectedItem;
//            this.Items.Add(string.Format("WI has been changed with value : {0} / {1} / {2} / {3}", this.SelectedText, this.SelectedIndex, this.SelectedItem, this.SelectedValue));
        }

        public void InvalidateDatasource()
        {
            // Réinitialise le champ à la valeur stockée sur le WI.
            if ((this.WorkItemDatasource as WorkItem) == null || (this.WorkItemDatasource as WorkItem).Fields[this.WorkItemFieldName] == null
                 || (this.WorkItemDatasource as WorkItem).Fields[this.WorkItemFieldName].Value == null)
            {
                return;
            }

            base.SelectedItem = (this.WorkItemDatasource as WorkItem).Fields[this.WorkItemFieldName].Value;
        }

        public void SetSite(IServiceProvider serviceProvider)
        {
            serviceProvider.GetService(typeof(IWorkItemControlHost));
        }
        #endregion
    }
}