WPF datatrigger not firing - wpf

Question

I'm trying to change the background colour of a text box in WPF based on its content.
Using breakpoints, I see my ValueConverter gets constructed, but neither Convert nor ConvertBack methods ever get called, and so the styling doesn't work.
The 'LightBlue' style in the XAML does work at startup.
I tried to use Snoop but I don't know what I'm looking for.
XAML...
<Grid.Resources>
<local:ThreadCreationLimitChanged x:Key="ThreadCreationLimitChanged"></local:ThreadCreationLimitChanged>
</Grid.Resources>
<Label Grid.Row="0" Grid.Column="0" Margin="0, 5, 0, 0" Content="New Thread Limit"></Label>
<TextBox Grid.Row="0" Grid.Column="1" Margin="10, 5, 10, 0" Width="100" Text="{Binding Path=ManagerConfig.ThreadCreationLimit, Mode=TwoWay, UpdateSourceTrigger=PropertyChanged}" >
<TextBox.Style>
<Style>
<Setter Property="TextBox.Background" Value="LightBlue"></Setter>
<Style.Triggers>
<DataTrigger Binding="{Binding Path=Text,Converter={StaticResource ThreadCreationLimitChanged}}" Value="false">
<Setter Property="TextBox.Background" Value="Yellow"></Setter>
</DataTrigger>
</Style.Triggers>
</Style>
</TextBox.Style>
</TextBox>
ValueConverter...
public class ThreadCreationLimitChanged : IValueConverter
{
public ThreadCreationLimitChanged()
{
}
public object Convert(object value, Type targetType, object parameter, System.Globalization.CultureInfo culture)
{
return value.ToString() == "120";
}
public object ConvertBack(object value, Type targetType, object parameter, System.Globalization.CultureInfo culture)
{
return null;
}
}
A bit of class ManagerConfig... (NotifyPropertyChanged implements INotifyPropertyChanged)
class ManagerConfig : NotifyPropertyChanged
{
private uint _ThreadCreationLimit;
public uint ThreadCreationLimit
{
get { return _ThreadCreationLimit; }
set
{
_ThreadCreationLimit = value;
OnPropertyChanged("ThreadCreationLimit");
}
}

Answer 1

Why not create a computed property on ManagerConfig which reports a status for the change of the ThreadCreationLimit? That way one doesn't need a converter. Code such as this:
public bool IsOverLimit { get { return ThreadCreationLimit > 120 } }
public uint ThreadCreationLimit
{
get { return _ThreadCreationLimit; }
set
{
_ThreadCreationLimit = value;
OnPropertyChanged("ThreadCreationLimit");
OnPropertyChanged("IsOverLimit");
}
}
Then bind the data trigger to IsOverLimit which will have a change notification sent everytime ThreadCreationLimit is set/changed.
An added plus is that the business logic is on the intended class and not a converter.

Answer 2

Change this {Binding Path=Text,Converter={StaticResource ThreadCreationLimitChanged}} to {Binding Path=Text, RelativeSource={RelativeSource Self} ,Converter={StaticResource ThreadCreationLimitChanged}}

Answer 3

I guess you are having Binding errors.Have checked like below,
1) Accessing TextBox directly for Value,
<Grid.Resources>
<local:ThreadCreationLimitChanged x:Key="ThreadCreationLimitChanged"></local:ThreadCreationLimitChanged>
</Grid.Resources>
<Label Grid.Row="0" Grid.Column="0" Margin="0, 5, 0, 0" Content="New Thread Limit"></Label>
<TextBox x:Name="tBox" Grid.Row="0" Grid.Column="1" Margin="10, 5, 10, 0" Width="100" Text="{Binding Path=ManagerConfig.ThreadCreationLimit, Mode=TwoWay, UpdateSourceTrigger=PropertyChanged}" >
<TextBox.Style>
<Style>
<Setter Property="TextBox.Background" Value="LightBlue"></Setter>
<Style.Triggers>
<DataTrigger Binding="{Binding Path=Text, ElementName=tBox,Converter={StaticResource ThreadCreationLimitChanged}}" Value="false">
<Setter Property="TextBox.Background" Value="Yellow"></Setter>
</DataTrigger>
</Style.Triggers>
</Style>
</TextBox.Style>
</TextBox>
2) Accesing proper Model values,
<Grid.Resources>
<local:ThreadCreationLimitChanged x:Key="ThreadCreationLimitChanged"></local:ThreadCreationLimitChanged>
</Grid.Resources>
<Label Grid.Row="0" Grid.Column="0" Margin="0, 5, 0, 0" Content="New Thread Limit"></Label>
<TextBox Grid.Row="0" Grid.Column="1" Margin="10, 5, 10, 0" Width="100" Text="{Binding Path=ManagerConfig.ThreadCreationLimit, Mode=TwoWay, UpdateSourceTrigger=PropertyChanged}" >
<TextBox.Style>
<Style>
<Setter Property="TextBox.Background" Value="LightBlue"></Setter>
<Style.Triggers>
<DataTrigger Binding="{Binding Path=ManagerConfig.ThreadCreationLimit,Converter={StaticResource ThreadCreationLimitChanged}}" Value="false">
<Setter Property="TextBox.Background" Value="Yellow"></Setter>
</DataTrigger>
</Style.Triggers>
</Style>
</TextBox.Style>
</TextBox>