private void ExecuteSaveStorageCommand(object param)
        {
            StorageAdded = false;

            if (_isNew)
            {
                ExternStorage = _dataAccess.CreateExternStorage(Name, CompanyName, Street, Number, ZipCode, City, CompanyId, TaxId);
                StorageAdded  = true;
            }
            else
            {
                ExternStorage.Name        = Name;
                ExternStorage.Prefix      = Prefix;
                ExternStorage.CompanyName = CompanyName;
                ExternStorage.Street      = Street ?? String.Empty;
                ExternStorage.Number      = Number;
                ExternStorage.ZipCode     = ZipCode;
                ExternStorage.City        = City;
                ExternStorage.CompanyId   = CompanyId ?? String.Empty;
                ExternStorage.TaxId       = TaxId ?? String.Empty;
                ExternStorage.Save();
            }

            IsValid = true;
            _closeAction();
        }