App.xaml

<Application x:Class="LocalIM.App"
             xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
             xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
             StartupUri="MainWindow.xaml">
    <Application.Resources>
        <Style TargetType="{x:Type Button}">
            <Setter Property="FontFamily" Value="Arial"/>
            <Setter Property="FontSize" Value="14"/>
            <Setter Property="Padding" Value="3,3,3,3"/>
        </Style>
        <Style x:Key="BasicTextBlock" TargetType="{x:Type TextBlock}">
            <Setter Property="FontFamily" Value="Arial"/>
            <Setter Property="FontSize" Value="14"/>
        </Style>
        <Style TargetType="{x:Type TextBlock}" BasedOn="{StaticResource BasicTextBlock}">
            
        </Style>        
    </Application.Resources>
</Application>