WPF DataGridColumn foreground color turn red if value is negative

Question

I want the foreground color of a DataGridColumn to change based on its value. I have

<DataGridTextColumn x:Name="Diff1" 
                    Binding="{Binding Change}" Header="Net Chng" 
                    Width="*" IsReadOnly="True"
                    Foreground="{Binding Change,Converter={StaticResource negativeToColor}}">
</DataGridTextColumn>

and the converter

public class negativeToColorConverter : IValueConverter
{
    public object Convert(object value, Type targetType, object parameter, System.Globalization.CultureInfo culture)
    {
        SolidColorBrush brush = new SolidColorBrush(Colors.LimeGreen);
        double doubleValue = 0.0;
        Double.TryParse(value.ToString(), out doubleValue);

        if (doubleValue < 0)
            brush = new SolidColorBrush(Colors.Red);

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

But the converter shows no effect.

Answer 1

its because all regular DataGridColumn Binding's are relative of the DataGrid element, not the Row. in The DataGrid level no property named Change, only in row level.

Solution is: using DataGridTemplateColumn.

<DataGridTemplateColumn Header="Net Chng" Width="*" IsReadOnly="True">
        <DataGridTemplateColumn.CellTemplate>
            <DataTemplate>
                <TextBlock Text="{Binding Change}" Foreground="{Binding Change, Converter={StaticResource negativeToColorConverter}}" />
            </DataTemplate>
        </DataGridTemplateColumn.CellTemplate>
</DataGridTemplateColumn>

EDIT: see Binding in a WPF data grid text column for more solutions.

Answer 2

foreground color of a DataGridColumn to change based on its value if value is negative then color is red other black xmal code is`

<Local:AlphabetTextColumn 
                        Header="  Contribution %"
                         x:Name="SalesaAmount2"
                        Binding="{Binding salesContribution}"                        
                        >

                    <DataGridTextColumn.ElementStyle>
                        <Style TargetType="{x:Type TextBlock}">
                            <Setter Property="Foreground" Value="{Binding ColorSet}" />                         
                        </Style>
                    </DataGridTextColumn.ElementStyle>
                </Local:AlphabetTextColumn>`

code in viewmodel is

 if(model.salesContribution<0)
{
model.ColorSet="Red";
}
else
{
model.ColorSet="Black";
}

add colorset variable is model

public string  ColorSet { get; set; }