Refresh style in datagrid bound to datatable WPF

I have a DataGrid bound to a DataTable and the DataGrid has a cellstyle that changes the Foreground of the numbers in the cells depending on its value (positive-black or negative-red). When the DataTable gets updated, the DataGrid is properly updated, so the binding is working fine. The problem is that the Style is just applied when the DataGrid is loaded the first time. When the DataGrid gets updated by the binding, if a negative number becomes a positive one, the Foreground remains red instead of becoming black.

Am I missing something, any propery or event?

Thanks in advance开发者_开发技巧.

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I am not sure how are you trying to do this.Any way i have tried and it is working fine.Check this code and find out what is going wrong

Xaml:

 <StackPanel Loaded="StackPanel_Loaded" >
    <StackPanel.Resources>
        <WpfApplication50:ValueToForegroundColorConverter x:Key="valueToForegroundColorConverter"/>
        <DataTemplate x:Key="Valuetemplate">
            <TextBlock x:Name="txt" Text="{Binding Value}" Foreground="{Binding Path=Value,Converter={StaticResource valueToForegroundColorConverter}}"/>
        </DataTemplate>
    </StackPanel.Resources>
    <dtgrd:DataGrid ItemsSource="{Binding Source}"  
                     Name="datagrid"                          
                     ColumnHeaderHeight="25" 
                     AutoGenerateColumns="False"   
                          >
        <dtgrd:DataGrid.Columns>
            <dtgrd:DataGridTemplateColumn CellTemplate="{StaticResource Valuetemplate}" Header="Value"/>
        </dtgrd:DataGrid.Columns>
    </dtgrd:DataGrid>
    <Button Height="30" Click="Button_Click"/>
</StackPanel>

and in your codebehind

 public partial class Window10 : Window,INotifyPropertyChanged
{  
    private DataTable source;
    public DataTable Source
    {
        get { return source; }
        set { source = value; OnPropertyChanged("Source"); }
    }
    public Window10()
    {
        InitializeComponent();
        this.DataContext = this;
    }
    #region INotifyPropertyChanged Members

    public event PropertyChangedEventHandler PropertyChanged;
    public void OnPropertyChanged(string name)
    {
        if(PropertyChanged!=null)
        PropertyChanged(this,new PropertyChangedEventArgs(name));
    }

    #endregion

    private void Button_Click(object sender, RoutedEventArgs e)
    {
        Source.Rows.Add("-1");
    }

    private void StackPanel_Loaded(object sender, RoutedEventArgs e)
    {
        Source = new DataTable();
        Source.Columns.Add("Value");
        Source.Rows.Add("1");
    }
}

also this converter

 class ValueToForegroundColorConverter : IValueConverter
{
    #region IValueConverter Members

    public object Convert(object value, Type targetType, object parameter, System.Globalization.CultureInfo culture)
    {
        SolidColorBrush brush = new SolidColorBrush(Colors.Black);
        int val = 0;
        int.TryParse(value.ToString(), out val);
        if (val < 0)
            brush = new SolidColorBrush(Colors.Red);
        return brush;
    }

    public object ConvertBack(object value, Type targetType, object parameter, System.Globalization.CultureInfo culture)
    {
        throw new NotImplementedException();
    }

    #endregion
}