Increase FontSize and FontWeight of DataGridColumnHeader

Question

The FontWeight of my DataGridColumnHeader is fine while developing in visual studio 2017 but once i launch the project, the text for the DataGridColumnHeader becomes faded. This is thesame for the DataGridComboBoxColumn. TextColumns work fine though. I found online that the best way to solve this problem is to use a TextBlock in the place of the DataGridColumnHeaderPresenter in the style of the DataGrid but i can'f find any help on how to acheive that.Also, No matter how much i increase the fontsize for the DataGridColumnHeader and the DataGridComboBoxColumn, it doesnt seem to change.

 

            I know some developers will say i should add the following fragment to my DataGrid 

<DataGrid.Resources>

   <Style TargetType="{x:Type DataGridColumnHeader}">

         <Setter Property="FontWeight" Value="Bold" />   

         <Setter Property="FontSize" Value="26" />

   </Style>

</DataGrid.Resources>

 

I have tried adding that but it doesn't work. I have edited the Template for the DataGrid, DataGridColumnHeader etc but no luck. Please i need urgent help.