private void AddMaterialCommand(object model) { ErrorMessage = ""; var material = model as Material; if (material.BillAmount <= 0 || material.Quantity <= 0 || string.IsNullOrWhiteSpace(material.BillNumber) || SelectedVendor.VendorId == 0 || material.SelectedMaterialType.MaterialTypeId == 0 || material.SelectedUnit.UnitId == 0) { ErrorMessage = "*Please check the entry. Some field's Values are missing."; return; } material.SelectedVendor = Vendors.Single(x => x.VendorId == SelectedVendor.VendorId); material.SiteId = SiteId; material.CreatedDate = DateTime.Now; _repositoryManager.AddMaterial(material); Materials = new ObservableCollection <Material>(_repositoryManager.GetMaterialBySiteId(SiteId)); MaterialToAdd = new Material(); MaterialToAdd.SelectedUnit = Units.First(); SelectedVendor = VendorList.First(); MaterialToAdd.SelectedMaterialType = MaterialTypes.First(); OnPropertyChanged(nameof(MaterialToAdd)); OnPropertyChanged(nameof(SelectedVendor)); }