更改WPF DataGrid单元格时如何更新总计摘要？

Question

I have a grid with total summaries. They update when a new row is entered. However, I want them to update as cells are changed in a new or existing row. I read a few articles and determined that handling the cell changed event and then running the UpdateTotalSummary method on the grid would do the trick, but it does not. Below is the code I am using and I verified that the code is being hit via debugging. Any help is appreciated:

<Grid DataContext="{Binding Source={StaticResource VM}}">
    <Grid.Resources>
        <local:TotalSumConverter x:Key="sumConverter" />
    </Grid.Resources>
    <Grid.RowDefinitions>
        <RowDefinition Height="*"/>
        <RowDefinition Height="auto"/>
    </Grid.RowDefinitions>
    <DataGrid x:Name="myGrid" AutoGenerateColumns="False" ItemsSource="{Binding TrsFundDocItems,Mode=TwoWay,UpdateSourceTrigger=PropertyChanged}">
        <DataGrid.Columns>
            <DataGridTextColumn Binding="{Binding Amount,Mode=TwoWay,UpdateSourceTrigger=PropertyChanged}" Header="Amount"/>
            <DataGridTextColumn Binding="{Binding FCAmount,Mode=TwoWay,UpdateSourceTrigger=PropertyChanged}" Header="FCAmount"/>
        </DataGrid.Columns>
    </DataGrid>
    <Grid Grid.RowSpan="2">
        <Grid.RowDefinitions>
            <RowDefinition Height="*"/>
            <RowDefinition Height="auto"/>
        </Grid.RowDefinitions>
        <Grid.ColumnDefinitions>
            <ColumnDefinition />
            <ColumnDefinition Width="auto"/>
        </Grid.ColumnDefinitions>
        <Grid Grid.Row="1" Grid.Column="1" Margin="8">
            <Grid.RowDefinitions>
                <RowDefinition/>
                <RowDefinition/>
            </Grid.RowDefinitions>
            <Grid.ColumnDefinitions>
                <ColumnDefinition Width="auto"/>
                <ColumnDefinition  Width="auto"/>
                <ColumnDefinition  Width="auto"/>
            </Grid.ColumnDefinitions>
            <TextBlock Text="SumTotal :" Grid.Row="0" Grid.Column="0"/>


            <TextBox Grid.Row="0" Grid.Column="1"  Text="{Binding ItemsSource, ConverterParameter=Amount, Converter={StaticResource sumConverter}, ElementName=myGrid, FallbackValue=0, Mode=TwoWay, UpdateSourceTrigger=PropertyChanged}" />

        </Grid>
    </Grid>
    </Grid>

This is my View Model :

public class WindowxViewModel : INotifyPropertyChanged
{
    public WindowxViewModel()
    {
        TrsFundDocItems = new ObservableCollection<TrsFundDocItem> { new TrsFundDocItem { Amount = 10, FCAmount = 1 }, new TrsFundDocItem { Amount = 5, FCAmount = 8 } };
    }


    private ObservableCollection<TrsFundDocItem> _TrsFundDocItems;

    public ObservableCollection<TrsFundDocItem> TrsFundDocItems
    {
        get { return _TrsFundDocItems; }
        set
        {
            if (_TrsFundDocItems == value) return;
            _TrsFundDocItems = value;
            PropertyChanged(this, new PropertyChangedEventArgs(nameof(TrsFundDocItems)));
        }
    }

    public event PropertyChangedEventHandler PropertyChanged = delegate { };
}

Converter :

////////////////
    public class TotalSumConverter : IValueConverter
    {
        public object Convert(object value, Type targetType, object parameter, CultureInfo culture)
        {
            var users = value as IEnumerable<object>;
            if (users == null)
                return "$0.00";

            double sum = 0;

            foreach (var u in users)
            {
                sum += ((TrsFundDocItem)u).Amount;
            }


            return sum.ToString("c");
        }

        public object ConvertBack(object value, Type targetType, object parameter, CultureInfo culture)
        {
            return 0;
        }
    }

Entity :

   public class TrsFundDocItem:INotifyPropertyChanged
    {
        //public double Amount { get; set; }
        private double amount;

        public double Amount
        {
            get { return amount; }
            set {
                if (amount == value) return;
                amount = value;
                PropertyChanged(this, new PropertyChangedEventArgs(nameof(Amount)));
            }
        }

        public double FCAmount { get; set; }

        public event PropertyChangedEventHandler PropertyChanged=delegate { };
    }

Answer 1

ItemsSource is not updated when you edit the cell. That is why TextBox binding does not work. Add TotalAmount property and Update method to the WindowxViewModel :

    public string TotalAmount
    {
        get { return _totalAmount; }
        set
        {
            if (_totalAmount == value) return;
            _totalAmount = value;
            PropertyChanged(this, new PropertyChangedEventArgs(nameof(TotalAmount)));
        }
    }

    private void UpdateAmount()
    {
        double sum = 0;

        foreach (var u in TrsFundDocItems)
        {
            sum += u.Amount;
        }


        TotalAmount = sum.ToString("c");
    }

Pass UpdateAmount method to TrsFundDocItem:

public class TrsFundDocItem : INotifyPropertyChanged
{
    private readonly Action _updateAction;

    //public double Amount { get; set; }
    private double amount;

    public TrsFundDocItem(Action updateAction)
    {
        _updateAction = updateAction;
    }
    public double Amount
    {
        get { return amount; }
        set
        {
            if (amount == value) return;
            amount = value;
            PropertyChanged(this, new PropertyChangedEventArgs(nameof(Amount)));
            _updateAction();
        }
    }

    public double FCAmount { get; set; }

    public event PropertyChangedEventHandler PropertyChanged = delegate { };
}

Update the binding:

<TextBox Grid.Row="0" Grid.Column="1"  Text="{Binding TotalAmount, FallbackValue=0, Mode=TwoWay, UpdateSourceTrigger=PropertyChanged}" />