c# - WPF DataGrid列总MVVM模式

Question

我的DataGrid中有一列是Price字段。
在表单底部的TextBlock中。

如何根据“价格”列的值在TextBlock中显示总值？

XAML代码:

 <Grid>
    <DataGrid HorizontalAlignment="Left" ItemsSource="{Binding Path=SaleryDetailsCollection, Mode=TwoWay}" AutoGenerateColumns="False" VerticalAlignment="Top" Width="640" Height="192" >
        <DataGrid.Columns>
            <DataGridTextColumn Header="Type" Binding="{Binding Type, Mode=TwoWay, NotifyOnTargetUpdated=True, ValidatesOnDataErrors=True}" Width="*" />
            <DataGridTextColumn Header="Amount" Binding="{Binding Price, Mode=TwoWay, NotifyOnTargetUpdated=True, ValidatesOnDataErrors=True}" Width="*" />
        </DataGrid.Columns>
    </DataGrid>
    <TextBlock HorizontalAlignment="Left" Margin="415,358,0,0" TextWrapping="Wrap" Text="{Binding SalaryTotal}" VerticalAlignment="Top"/>
</Grid>

ViewModel:

public ObservableCollection<SaleryDetailsModel> SaleryDetailsCollection
{
    get { return _SaleryDetailsCollection; }
    set
    {
        SalaryTotal = SaleryDetailsCollection.Sum(x => x.Amount);
        _SaleryDetailsCollection = value;
        NotifyPropertyChanged("SaleryDetailsCollection");
    }
}
public Double SalaryTotal
{
    get { return _SalaryTotal; }
    set
    {
        _SalaryTotal = value;
        NotifyPropertyChanged("SalaryTotal");
    }
}

类SaleryDetailsMode

  class SaleryDetailsModel:ViewModel
{
    private Double _Amount;
    private String _Type;
    public Double Amount
    {
        get { return _Amount; }
        set
        {
            _Amount = value;
            NotifyPropertyChanged("Amount");
        }
    }
    public String Type { get { return _Type; } set { _Type = value; NotifyPropertyChanged("Type"); } }

}

类ViewModel

public class ViewModel : INotifyPropertyChanged
{
    public event PropertyChangedEventHandler PropertyChanged;

    protected void NotifyPropertyChanged(string propertyName)
    {
        if (this.PropertyChanged != null)
            this.PropertyChanged(this, new PropertyChangedEventArgs(propertyName));
    }
}

Answer 1

将此代码添加到构造函数中

SaleryDetailsCollection = new ObservableCollection<SaleryDetailsModel>();
SaleryDetailsCollection.CollectionChanged += MyItemsSource_CollectionChanged;

在ViewModel中

void MyItemsSource_CollectionChanged(object sender, NotifyCollectionChangedEventArgs e)
    {
        if (e.NewItems != null)
            foreach (SaleryDetailsModel item in e.NewItems)
                item.PropertyChanged += MyType_PropertyChanged;

        if (e.OldItems != null)
            foreach (SaleryDetailsModel item in e.OldItems)
                item.PropertyChanged -= MyType_PropertyChanged;
    }

void MyType_PropertyChanged(object sender, PropertyChangedEventArgs e)
    {
        if (e.PropertyName == "Amount")
            DoWork();
    }

    private void DoWork()
    {
        SalaryTotal = SaleryDetailsCollection.Sum(x => x.Amount);
    }

XAML

<Grid>
<DataGrid HorizontalAlignment="Left" ItemsSource="{Binding Path=SaleryDetailsCollection, Mode=TwoWay}" AutoGenerateColumns="False" VerticalAlignment="Top" Width="640" Height="192" >
    <DataGrid.Columns>
        <DataGridTextColumn Header="Type" Binding="{Binding Type, Mode=TwoWay, UpdateSourceTrigger=PropertyChanged, ValidatesOnDataErrors=True}" Width="*" />
        <DataGridTextColumn Header="Amount" Binding="{Binding Price, Mode=TwoWay, UpdateSourceTrigger=PropertyChanged, ValidatesOnDataErrors=True}" Width="*" />
    </DataGrid.Columns>
</DataGrid>
<TextBlock HorizontalAlignment="Left" Margin="415,358,0,0" TextWrapping="Wrap" Text="{Binding SalaryTotal}" VerticalAlignment="Top"/>