WPF textbox's toolip foreground not changing - wpf

Question

I have created a customized textbox which have a property SelfPropertyInfo. This again have some other property which we use(like IsValid, Description etc). I am trying to add style on text box so that if if IsValid is false it should show a tooltip(which contains Description).
<Style TargetType="{x:Type ToolTip}">
<Setter Property = "Foreground" Value=" Red "/>
</Style>
<Style TargetType="{x:Type CustomControls:TextBox}">
<Setter Property="Height" Value="22"/>
<Setter Property="Margin" Value="2,2,2,2"/>
<Style.Triggers>
<Trigger Property="IsEnabled" Value="False">
<Setter Property="Background" Value="DarkGray" />
</Trigger>
<DataTrigger Binding="{Binding RelativeSource={RelativeSource Self}, Path=SelfPropertyInfo.IsValid}" Value="False">
<Setter Property="BorderBrush" Value="Red"/>
<Setter Property="BorderThickness" Value="1"/>
<Setter Property="ToolTip" Value="{Binding RelativeSource={RelativeSource Self}, Path=SelfPropertyInfo.RuleDescription}" >
</Setter>
</DataTrigger>
</Style.Triggers>
</Style>
By above code everything is working fine, but the issue is that the tooltip is not in "Red" color. :(
Can anybody suggest?
I tried another approach and the foreground is now "Red", but I need help about how TO bind description with tootip's text. Please see the changes inside DataTrigger, :
<DataTrigger Binding="{Binding RelativeSource={RelativeSource Self}, Path=SelfPropertyInfo.IsValid}" Value="False">
<Setter Property="BorderBrush" Value="Red"/>
<Setter Property="BorderThickness" Value="1"/>
<Setter Property="ToolTip">
<Setter.Value>
<ToolTip >
<TextBlock Foreground="Red" Text="Hello"/>
</ToolTip>
</Setter.Value>
</Setter>
</DataTrigger>
Thanks in advance for any help.
I also tried below code, but it makes tooltip blank:
<DataTrigger Binding="{Binding RelativeSource={RelativeSource Self}, Path=SelfPropertyInfo.IsValid}" Value="False">
<Setter Property="BorderBrush" Value="Red"/>
<Setter Property="BorderThickness" Value="1"/>
<Setter Property="ToolTip">
<Setter.Value>
<ToolTip >
<TextBlock Foreground="Red" Text="{Binding RelativeSource={RelativeSource Self}, Path=SelfPropertyInfo.RuleDescription}"/>
</ToolTip>
</Setter.Value>
</Setter>

Answer 1

In the DataTrigger, "Text" property of TextBlock used to set Foreground for tooltip is overriding the Tooltip's text value, thats why you're unable to see the description. So bind the "Text" property with SelfPropertyInfo.RuleDescription.

Answer 2

I tried out using normal property it worked fine for me
private string testString;
public string TestString
{
get { return testString; }
set
{
testString = value;
RaisePropertyChanged("TestString");
}
}
<TextBox Height="100" Text="{Binding TestString}">
<TextBox.Style>
<Style TargetType="{x:Type TextBox}">
<Style.Triggers>
<DataTrigger Binding="{Binding TestString}" Value="False">
<Setter Property="BorderBrush" Value="Red"/>
<Setter Property="BorderThickness" Value="1"/>
<Setter Property="ToolTip">
<Setter.Value>
<ToolTip >
<TextBlock Foreground="Red" Text="{Binding TestString}"/>
</ToolTip>
</Setter.Value>
</Setter>
</DataTrigger>
</Style.Triggers>
</Style>
</TextBox.Style>
</TextBox>