c# - 无法更新数据网格并将更改保存到数据库

Question

我有一个数据网格、一个 ViewModel 中产品类型的 ObservableCollection 和一个 EventToCommand 的实现，如下所示。我想从 Quantity 和 Cost Column 的乘积更新 Total Column 并保存更改，而不使用背后的恶意代码或 Windows Forms DataGridView。我怎样才能做到这一点？数据网格:

<DataGrid x:Name="dataGrid" Margin="5,5,10,5" AutoGenerateColumns="False"  HorizontalAlignment="Stretch" ItemsSource="{Binding ProductList, Mode=TwoWay, UpdateSourceTrigger=PropertyChanged}" VerticalAlignment="Stretch" Height="566"  >
<i:Interaction.Triggers>
     <i:EventTrigger EventName="CellEditEnding" SourceObject="{Binding ElementName=Control}">
        <cmd:EventToCommand Command="{Binding EndEdit}" PassEventArgsToCommand="True"/>
     </i:EventTrigger>
</i:Interaction.Triggers>
<DataGrid.Columns>
  <DataGridTextColumn x:Name="Id" Binding="{Binding Path=Id, Mode=TwoWay}" Header="Id"/>
    <DataGridTextColumn x:Name="name" Binding="{Binding Path=Name, Mode=TwoWay}" Header="Name"/>
    <DataGridTextColumn x:Name="cost" Binding="{Binding Path=Cost, Mode=TwoWay}" Header="Cost"/>
    <DataGridTextColumn x:Name="Quantity" Binding="{Binding Path=Quantity, Mode=TwoWay}" Header="Quantity"/>
    <DataGridTextColumn x:Name="total" Binding="{Binding Path=Total, Mode=TwoWay}" Header="Total"/>
</DataGrid.Columns>

然后在 ViewModel 中

 private ObservableCollection<Product> _product;
    public ObservableCollection<Product> MyProduct
    {
        get
        {
            return _product;
        }
        set
        {
            Set(ref _product, value);
        }
    }

public ProductViewModel(IDataService proxy)
    {
        _proxy = proxy;

        LoadCommand = new RelayCommand(DoGetProducts);
        EndEdit = new RelayCommand<DataGridCellEditEndingEventArgs>(DoEndEdit);

    }

    private void DoEndEdit(DataGridCellEditEndingEventArgs obj)
    {
        DataGridRow row = obj.Row;
        Product p = (Product)row.Item;
        p.Total = p.Cost*p.Quantity;
        _proxy.SaveAll();
    }

然后在模型中:

public class DataService : IDataService
{
    ProductEntities context;
    public DataService()
    {
        context = new ProductEntities();
    }
    public ObservableCollection<Product> GetProducts(){
        ObservableCollection<Product> products = new ObservableCollection<Product>();
            foreach(var p in context.Products.Tolist()){
                products.add(p);
            }
        return products;
    }
    public void SaveAll()
    {
        context.SaveChanges();
    }
}

当成本和数量发生变化时，数据网格正在加载产品但不会更新总计。此外，不保存数据库中的更改

Answer 1

要更新 DataGrid 中的“总计”列，Product 类应实现 INotifyPropertyChanged接口(interface)并引发 Total 属性的 PropertyChanged 事件:

private double _total;
public double Total
{
    get { return _total; }
    set { _total = value; OnPropertyChanged("Total"); }
}

为了能够将值保存到数据库中，您需要将 Total 属性映射到数据库表中的列，就像您(希望)对其他列所做的那样.