update listItem file

Hi,

I have an issue with listItem file update ?

I have to update file attached to listItem. But sometimes a new file is created with the default contenttype in the documentset.

Here the code i use.

using (SPSite site = new SPSite(missionOrder.Web.Site.ID))
                        using (SPWeb web = site.OpenWeb(missionOrder.Web.ID))
                        {
                            bool allowUnsafeUpdate = web.AllowUnsafeUpdates;
                            bool parserEnabled = web.ParserEnabled;

                            try
                            {
                                web.AllowUnsafeUpdates = true;
                                web.ParserEnabled = false;
                                web.Update();

                                SPListItem item = web.Lists[missionOrder.ParentList.ID].GetItemById(missionOrder.ID);

                                item.File.SaveBinary(docmStream);
                                item.File.Update();

                                //fix for eventReceiver
                                int nbrOftry = 0;
                                item = web.Lists[missionOrder.ParentList.ID].GetItemById(missionOrder.ID);

                                while (item.File.ParentFolder.Name.Equals("Technique") == false || nbrOftry == 3)
                                {
                                    System.Threading.Thread.Sleep(1000);
                                    item = web.Lists[missionOrder.ParentList.ID].GetItemById(missionOrder.ID);
                                    nbrOftry++;
                                }
//updating metadata and ContentType
                                SPContentType missionOrderCT = missionOrder.ParentList.ContentTypes["MissionOrder"];

                                item["ProjIDAffaire"] = affaireID;
                                item["MissionOrderID"] = missionID;
                                item["ContentTypeId"] = missionOrderCT.Id.ToString();
                                item["SynchroVersNomade"] = "True";
                                item.UpdateOverwriteVersion();

                                item = web.Lists[missionOrder.ParentList.ID].GetItemById(missionOrder.ID);

                                //Delete old item version.
                                try
                                {
                                    SPListItemVersionCollection coll = item.Versions;

                                    for (int i = 0; i < item.Versions.Count; i++)
                                    {
                                        if (!coll[1].IsCurrentVersion)
                                            coll[1].Delete();
                                    }
                                }
                                catch { }


                                web.ParserEnabled = parserEnabled;
                                web.AllowUnsafeUpdates = allowUnsafeUpdate;
                                web.Update();
                            }
                            catch (Exception)
                            {
                                web.ParserEnabled = parserEnabled;
                                web.AllowUnsafeUpdates = allowUnsafeUpdate;
                                web.Update();
                            }
                        }

Regards,

J.D.