Zachet/DB/App.xaml

<Application x:Class="DB.App"
             xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
             xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
             xmlns:local="clr-namespace:DB"
             StartupUri="MainWindow.xaml">
    <Application.Resources>
        <Style x:Key="TBStyle" TargetType="TextBox">
            <Setter Property="Height" Value="30"/>
            <Setter Property="Width" Value="150"/>
        </Style>
    </Application.Resources>
</Application>