Highlighting cells in WPF DataGrid when the bound value changes

datagrid, mvvm, storyboard, wpf

Solution

Since `TargetUpdated` is truly only UI update based event. It doesn't matter how update is happening. While sorting all the `DataGridCells` remain at their places only data is changed in them according to sorting result hence `TargetUpdated`is raised. hence we have to be dependent on data layer of WPF app. To achieve this I've reset the Binding of `DataGridCell` based on a variable that kind of trace if update is happening at data layer.

XAML:

<Window.Resources>
    <Style x:Key="ChangedCellStyle" TargetType="DataGridCell">
        <Setter Property="Template">
            <Setter.Value>
                <ControlTemplate TargetType="DataGridCell">
                    <ControlTemplate.Triggers>
                        <EventTrigger RoutedEvent="Binding.TargetUpdated">
                            <BeginStoryboard>
                                <Storyboard>
                                    <ColorAnimation Duration="00:00:04" Storyboard.TargetName="myTxt"
                                        Storyboard.TargetProperty="(DataGridCell.Background).(SolidColorBrush.Color)" 
                                        From="Red" To="Transparent" />
                                </Storyboard>
                            </BeginStoryboard>
                        </EventTrigger>                           
                    </ControlTemplate.Triggers>

                    <TextBox HorizontalAlignment="Stretch" VerticalAlignment="Stretch" Background="Transparent"
                             Name="myTxt" >
                        <TextBox.Style>
                            <Style TargetType="TextBox">
                                <Style.Triggers>
                                    <DataTrigger Binding="{Binding RelativeSource={RelativeSource Mode=TemplatedParent},Path=DataContext.SourceUpdating}" Value="True">
                                        <Setter Property="Text" Value="{Binding RelativeSource={RelativeSource Mode=TemplatedParent},Path=Content.Text,NotifyOnSourceUpdated=True,NotifyOnTargetUpdated=True}" />
                                    </DataTrigger>
                                    <DataTrigger Binding="{Binding RelativeSource={RelativeSource Mode=TemplatedParent},Path=DataContext.SourceUpdating}" Value="False">
                                        <Setter Property="Text" Value="{Binding RelativeSource={RelativeSource Mode=TemplatedParent},Path=Content.Text}" />                                            
                                    </DataTrigger>                                       
                                </Style.Triggers>                                    
                            </Style>
                        </TextBox.Style>
                    </TextBox>
                </ControlTemplate>
            </Setter.Value>
        </Setter>
    </Style>
</Window.Resources>

<StackPanel Orientation="Vertical">
    <DataGrid ItemsSource="{Binding list}" CellStyle="{StaticResource ChangedCellStyle}" AutoGenerateColumns="False"
              Name="myGrid"  >
        <DataGrid.Columns>
            <DataGridTextColumn Header="Name" Binding="{Binding Name}" />
            <DataGridTextColumn Header="ID" Binding="{Binding Id}" />
        </DataGrid.Columns>
    </DataGrid>
    <Button Content="Change Values" Click="Button_Click" />
</StackPanel>

Code Behind(DataContext object of Window):

 public MainWindow()
    {
        list = new ObservableCollection<MyClass>();
        list.Add(new MyClass() { Id = 1, Name = "aa" });
        list.Add(new MyClass() { Id = 2, Name = "bb" });
        list.Add(new MyClass() { Id = 3, Name = "cc" });
        list.Add(new MyClass() { Id = 4, Name = "dd" });
        list.Add(new MyClass() { Id = 5, Name = "ee" });
        list.Add(new MyClass() { Id = 6, Name = "ff" });   
        InitializeComponent();
    }

    private ObservableCollection<MyClass> _list;
    public ObservableCollection<MyClass> list
    {
        get{ return _list; }
        set{   
            _list = value;
            updateProperty("list");
        }
    }
   
    Random r = new Random(0);
    private void Button_Click(object sender, RoutedEventArgs e)
    {

        int id = (int)r.Next(6);
        list[id].Id += 1;
        int name = (int)r.Next(6);
        list[name].Name = "update " + r.Next(20000);
    }

Model Class: `SourceUpdating` property is set to true(which set the binding to notify `TargetUpdate` via a `DataTrigger`) when any notification is in progress for `MyClass` in `updateProperty()` method and after update is notified to `UI`, `SourceUpdating` is set to false(which then reset the binding to not notify `TargetUpdate` via a `DataTrigger`).

public class MyClass : INotifyPropertyChanged
{
    private string name;
    public string Name
    {
        get { return name; }
        set { 
            name = value;updateProperty("Name");
        }
    }

    private int id;
    public int Id
    {
        get { return id; }
        set 
        { 
            id = value;updateProperty("Id");
        }
    }

    //the vaiable must set to ture when update in this calss is ion progress
    private bool sourceUpdating;
    public bool SourceUpdating
    {
        get { return sourceUpdating; }
        set 
        { 
            sourceUpdating = value;updateProperty("SourceUpdating");
        }
    }        

    public event PropertyChangedEventHandler PropertyChanged;
    public void updateProperty(string name)
    {
        if (name == "SourceUpdating")
        {
            if (PropertyChanged != null)
            {
                PropertyChanged(this, new PropertyChangedEventArgs(name));
            }
        }
        else
        {
            SourceUpdating = true;               
            if (PropertyChanged != null)
            {
                PropertyChanged(this, new PropertyChangedEventArgs(name));
            }               
           SourceUpdating = false;                
        }
    }

}

Outputs:

Two simultaneous Updates/ Button is clicked once :

Many simultaneous Updates/ Button is clicked many times :

SO after update, when sorting or filtering is happening the bindings know that it doesn't have to invoke the `TargetUpdated` event. Only when the update of source collection is in progress the binding is reset to invoke the `TargetUpdated` event. Also initial coloring problem is also get handled by this.

However as the logic still has some sort comings as for editor `TextBox` the logic is based on with more complexity of data types and UI logic the code will become more complex also for initial binding reset whole row is animated as `TargetUpdated` is raised for all cells of a row.

Problem

Original source