cannot set tooltip in style - wpf

Question

I searched and find out I can't set the tooltip in setter.value directly (in a style.xaml file). However I can use static resource to set the tooltip.
My question is, since I need to supply dynamic text for the tooltip, I can't use static resource. How should I do that?
here is my example.
<Style x:Key="ErrorStyleRadius" TargetType="{x:Type FrameworkElement}">
<Style.Triggers>
<MultiDataTrigger>
<MultiDataTrigger.Conditions>
<Condition Binding="{Binding (Validation.HasError), RelativeSource={RelativeSource Mode=Self}}" Value="True"/>
<Condition Binding="{Binding (Validation.Errors), RelativeSource={RelativeSource Mode=Self}, Converter={StaticResource IsError}}" Value="True"/>
</MultiDataTrigger.Conditions>
<MultiDataTrigger.Setters>
<Setter Property="ToolTip">
<Setter.Value>
<ToolTip>
<Label Content="{Binding somePropertyHere}"/>
</ToolTip>
</Setter.Value>
</Setter>
<Setter Property="Validation.ErrorTemplate" Value="{StaticResource ErrorControlTemplateRadiusError}"/>
</MultiDataTrigger.Setters>
</MultiDataTrigger>
<MultiDataTrigger>
<MultiDataTrigger.Conditions>
<Condition Binding="{Binding (Validation.HasError), RelativeSource={RelativeSource Mode=Self}}" Value="True"/>
<Condition Binding="{Binding (Validation.Errors), RelativeSource={RelativeSource Mode=Self}, Converter={StaticResource IsWarning}}" Value="True"/>
</MultiDataTrigger.Conditions>
<MultiDataTrigger.Setters>
<Setter Property="ToolTip" Value="{Binding RelativeSource={RelativeSource Self}, Path=(Validation.Errors), Converter={StaticResource ValMsg}}"/>
<Setter Property="Validation.ErrorTemplate" Value="{StaticResource ErrorControlTemplateRadiusWarning}"/>
</MultiDataTrigger.Setters>
</MultiDataTrigger>
</Style.Triggers>
</Style>
for usage, i can use as
<textbox style={staticresource ErrorStyleRadius} text={bind name, validationOnDataError=true}/>

Answer 1

Why don't you try this -
<ToolTip x:Key="MyToolTip"
DataContext={Binding PlacementTarget, RelativeSource={RelativeSource Self}}>
<Label Content="{Binding Text}"/>
</ToolTip>
<Style x:Key="ErrorStyleRadius" TargetType="{x:Type FrameworkElement}">
<Style.Triggers>
<MultiDataTrigger>
<MultiDataTrigger.Conditions>
<Condition Binding="{Binding (Validation.HasError), RelativeSource={RelativeSource Mode=Self}}" Value="True"/>
<Condition Binding="{Binding (Validation.Errors), RelativeSource={RelativeSource Mode=Self}, Converter={StaticResource IsError}}" Value="True"/>
</MultiDataTrigger.Conditions>
<MultiDataTrigger.Setters>
<Setter Property="ToolTip" Value={StaticResource MyToolTip}>
</Setter>
<Setter Property="Validation.ErrorTemplate" Value="{StaticResource ErrorControlTemplateRadiusError}"/>
</MultiDataTrigger.Setters>
</MultiDataTrigger>
</Style.Triggers>
</Style>
You can give the property name in StaticResource. It will update the tooltip dynamically.

Answer 2

Also you can set the tooltip from your style if you want to set the text to Validation.Error like this -
<Trigger Property="Validation.HasError" Value="True">
<Setter Property="ToolTip"
Value="{Binding RelativeSource={RelativeSource Self},
Path=(Validation.Errors)[0].ErrorContent}" />
</Trigger>