WPF Style BasedOn parent Style in current context - wpf

Question

Say, I have a default style for a TextBox 'TextBoxStyleBase'.
I then define a DataGrid style which has an own TextBox style BasedOn that Base-style, defining another Border Color.
In some place inside a DataGrid I want to define another TextBox style but inherit from the one defined in DataGrid style.
Is there a way to make a style inherit from the style that is currently defined for a specific control in the current 'context'?
EDIT:
To make it more clear, here's what I have:
<!-- explicit style for all TextBoxes -->
<Style TargetType="{x:Type TextBox}" x:Key="TextStyle">
<Setter Property="FontSize" Value="16"/>
</Style>
<!-- implicit style for all TextBoxes -->
<Style TargetType="{x:Type TextBox}" BasedOn="{StaticResource TextStyle}"/>
<!-- DataGrid style changing inner TextBox style -->
<Style TargetType="{x:Type DataGrid}">
<Style.Resources>
<Style TargetType="{x:Type TextBox}" BasedOn="{StaticResource TextStyle}">
<Setter Property="FontSize" Value="20"/>
</Style>
<!-- since TextBox has defined implicit style this would be equivalent to -->
<!--<Style TargetType="{x:Type TextBox}" BasedOn="{StaticResource {x:Type TextBox}}">
<Setter Property="FontSize" Value="20"/>
</Style>-->
</Style.Resources>
</Style>
<Control>
<DataGrid>
<Row>
<TextBox/> <!-- should show as defined in DataGrid style -->
</Row>
<Row>
<Row.Resources>
<Style TargetType="{x:Type TextBox}" BasedOn=" ??? ">
<Style.Triggers>
<Trigger Property="IsMouseOver" Value="True">
<Setter Property="FontWeight" Value="Bold"/>
</Trigger>
</Style.Triggers>
</Style>
</Row.Resources>
<TextBox/> <!-- should show with additional trigger -->
</Row>
</DataGrid>
</Control>
What to put in BasedOn = '???' so that the text shows up in FontSize 20 but Bold if hovered.

Answer 1

You cannot add two Styles with the same key inside the same ResourceDictionary. So if you already have defined an implicit Style without an x:Key in a ResourceDictionary for a specific type, you cannot add another one to the same ResourceDictionary.
Otherwise you should be able to base a Style on the default style that is in scope like this:
<Style TargetType="TextBox" BasedOn="{StaticResource {x:Type TextBox}}">
<Style.Triggers>
</Style.Triggers>
</Style>

Answer 2

Please use the following for the textbox inside the datagrid:
<Style TargetType="TextBox" BasedOn="{StaticResource <your style name>}">
PS: would be TextBoxStyleBase in your case.