I'm trying to change the text colour in a datagrid depending on a bool in my model using a converter but I get the following error.

System.Windows.Data Error: 2 : Cannot find governing FrameworkElement or FrameworkContentElement for target element. BindingExpression:Path=DiameterCustom; DataItem=null; target element is 'DataGridTextColumn' (HashCode=7886611); target property is 'Foreground' (type 'Brush')

Does anyone know why this is?

My xaml is as follows:

<UserControl.Resources>
    <conv:UnitConverter x:Key="UnitConverter"></conv:UnitConverter>
    <conv:CustomColourConverter x:Key="CustomColourConverter"></conv:CustomColourConverter>
</UserControl.Resources>

<DataGridTextColumn 
  Header="Diameter &#x0a;(mm)"  
  Binding="{Binding Diameter, Mode=TwoWay, StringFormat={}{0:n0}, Converter={StaticResource UnitConverter}, ConverterParameter=1000}" 
  Foreground="{Binding DiameterCustom, Converter={StaticResource CustomColourConverter}}"/>

This is my converter:

public object Convert(object value, Type targetType, object parameter, CultureInfo culture)
{
    bool v = (bool)value;

    if (v == true)
    {            
       //return return System.Windows.Media.Brushes.Red;
       return new SolidColorBrush(Colors.Red);            
    }

  //return return System.Windows.Media.Brushes.Blue;
  return new SolidColorBrush(Colors.Blue);
}

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

and just for completeness, here is my model property:

private bool diameterCustom;

public bool DiameterCustom
{
   get { return diameterCustom; }
   set { SetAndNotify(ref this.diameterCustom, value); }
}

Note, the data binding for Diameter and the unit converter work fine.

CodePudding user response：

To change the text colour cell by cell the following solution worked:

<DataGridTextColumn 
    Header="Diameter &#x0a;(mm)"  
    Binding="{Binding Diameter, Mode=TwoWay, StringFormat={}{0:n0}, Converter={StaticResource UnitConverter}, ConverterParameter=1000}">
    <DataGridTextColumn.ElementStyle>
        <Style TargetType="{x:Type TextBlock}">
            <Setter Property="Foreground" Value="{Binding DiameterCustom, Converter={StaticResource CustomColourConverter}}"/>
        </Style>
    </DataGridTextColumn.ElementStyle>
</DataGridTextColumn>