单元格值更改时如何更新DataGrid单元格背景

Question

All, I have the following XAML to change the cells background colour at run-time based on whether the cells content is 'Help'.

<UserControl.Resources>
  <local:CellColorConverter x:Key ="cellColorConverter"/>
</UserControl.Resources>

   <DataGrid x:Name="dataGrid" AlternatingRowBackground="Gainsboro" 
       AlternationCount="2" HorizontalAlignment="Stretch"
       VerticalAlignment="Stretch">
    <DataGrid.CellStyle>
       <Style TargetType="DataGridCell" >
          <Setter Property="Background">
             <Setter.Value>
                <MultiBinding Converter="{StaticResource cellColorConverter}" >
                   <MultiBinding.Bindings>
                      <Binding RelativeSource="{RelativeSource Self}"/>
                      <Binding Path="Row"/>
                   </MultiBinding.Bindings>
                </MultiBinding>
             </Setter.Value>
          </Setter>
          <Style.Triggers>
             <Trigger Property="IsSelected" Value="True">
                <Setter Property="Background" Value="#FF007ACC"/>
                <Setter Property="Foreground" Value="White"/>
             </Trigger>
          </Style.Triggers>
       </Style>
    </DataGrid.CellStyle>
</DataGrid>

The CellColorConverter class handle the 'converion'/colour update.

public class CellColorConverter : IMultiValueConverter
{
    public object Convert(object[] values, Type targetType, object parameter, CultureInfo culture)
    {
        if (values[1] is DataRow)
        {
            //Change the background of any cell with 1.0 to light red.
            var cell = (DataGridCell)values[0];
            var row = (DataRow)values[1];
            var columnName = cell.Column.SortMemberPath;
            if (row[columnName].ToString().CompareTo("Help") == 0)
                return new SolidColorBrush(Colors.LightSalmon);
        }
        return SystemColors.AppWorkspaceColor;
    }

    public object[] ConvertBack(object value, Type[] targetTypes, object parameter, CultureInfo culture)
    {
     throw new System.NotImplementedException();
    }
}

This works when the data is loaded in, but I also want the colour to be updated if the user types 'Help' into a cell. So I have tried amending the binding to

<Setter Property="Background">
    <Setter.Value>
         <MultiBinding Converter="{StaticResource cellColorConverter}" >
              <MultiBinding.Bindings>
                   <Binding RelativeSource="{RelativeSource Self}" // Changed this!
                            Mode="TwoWay" UpdateSourceTrigger="PropertyChanged"/>
                   <Binding Path="Row"/>
              </MultiBinding.Bindings>
         </MultiBinding>
     </Setter.Value>

But this has not worked. How to I get the background cell colour to change when the cell value is changed and committed?

Thanks for your time.

Answer 1

If I can assume your data grid is bound to a collection of items in a view model, then for a specific column you can use a DataTrigger:

<DataGrid ItemsSource="{Binding Items}" ...>
    <DataGrid.Columns>
        ... columns
        <DataGridTextColumn Header="My column" 
            Binding="{Binding MyItem, UpdateSourceTrigger=PropertyChanged}">
            <DataGridTextColumn.CellStyle>
                <Style TargetType="{x:Type DataGridCell}">
                    <Style.Triggers>
                        <DataTrigger Binding="{Binding MyItem}" Value="Help">
                            <Setter Property="Background" Value="LightSalmon"/>
                        </DataTrigger>
                    </Style.Triggers>
                </Style>
            </DataGridTextColumn.CellStyle>
        </DataGridTextColumn>

The problem would be if you needed to apply this to all columns, in which case you would need a separate style for each.