How to make conditional DataTrigger in WPF

Question

I wanna make coloring DataGridRow in my datagrid using style in WPF. I wanna make percentage of coloring based on value. If I have value binding Error between 0 and 50 it will be red. And if vice versa it will be colored as Green

But How I can do with style?

 <Style TargetType="DataGridRow">
                <Style.Triggers>
                    <DataTrigger Binding="{Binding Error}" Value="Error>50"> //maybe something like this
                        <Setter Property="Foreground" Value="#FFE08F8F" />
                    </DataTrigger>
                    <DataTrigger Binding="{Binding Error}" Value="2">
                        <Setter Property="Foreground" Value="#FF6DBB6D" />
                    </DataTrigger>
                </Style.Triggers>
            </Style>

Answer 1

IMO the most flexible solution will be to add some kind of ErrorToColor converter. Then use this XAML:

<Setter Property="Foreground" >
    <Setter.Value>
        <SolidColorBrush Color="{Binding Error, Converter={StaticResource errorToColorConverter}}" />
    </Setter.Value>
</Setter>

Such converter could look like this:

public class IntToColorConverter : IValueConverter
{
    public object Convert(object value, Type targetType, object parameter, System.Globalization.CultureInfo culture)
    {            
        return value is int && ((int)value) > 50 ? Colors.Green : Colors.Red;
    }

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

This way you can easily manage colors for different error values.

Answer 2

You will need a custom converter that will convert Error to some value indicating the error state; the following converter will return True when Error is greater than 50:

public class ErrorConverter : IValueConverter
{
    public object Convert(object value, Type targetType, object parameter, CultureInfo culture)
    {
        return System.Convert.ToInt(value) > 50;
    }

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

Now reference this in the resources (and True helper, you might not need this, can't remember if the conversion is automatic):

<system:Boolean x:Key="True">True</system:Boolean>
<local:ErrorConverter x:Key="ErrorConverter">

And bind it up like this:

<Style TargetType="DataGridRow">
    <Style.Triggers>
        <DataTrigger 
            Binding="{Binding Error, Converter={StaticResource ErrorConverter}}" 
            Value="{StaticResource True}">
            <Setter Property="Foreground" Value="#FFE08F8F" />
        </DataTrigger>
        <DataTrigger Binding="{Binding Error}" Value="2">
            <Setter Property="Foreground" Value="#FF6DBB6D" />
        </DataTrigger>
    </Style.Triggers>
</Style>

Something along those lines should work.