Project41P2023/MyWpfApp/Pages/PageForBindings.xaml

<Page x:Class="MyWpfApp.Pages.PageForBindings"
      xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
      xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
      xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006" 
      xmlns:d="http://schemas.microsoft.com/expression/blend/2008" 
      xmlns:local="clr-namespace:MyWpfApp.Pages"
      mc:Ignorable="d" 
      d:DesignHeight="450" d:DesignWidth="800"
      Title="PageForBindings">

    <StackPanel>
        <TextBox x:Name="txtOut" FontSize="{Binding Value, ElementName=sl1}" Text="{Binding Name}"/>
        <TextBox x:Name="txtIn" FontSize="{Binding Value, ElementName=sl1}" Text="{Binding Login}"/>
        <Slider x:Name="sl1" Maximum="100" Minimum="10" Value="20"/>
        <Button Content="Сохранить изменения" Click="Button_Click"/>
    </StackPanel>
</Page>