15/MainWindow.xaml

<Window x:Class="Praktika13_Chistyakov.MainWindow"
        xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
        xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
        xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
        xmlns:local="clr-namespace:Praktika13_Chistyakov"
        mc:Ignorable="d"
        Title="MainWindow" Height="450" Width="800">
    <Grid HorizontalAlignment="Left" Width="792">
        <Grid.RowDefinitions>
            <RowDefinition Height="186"/>
            <RowDefinition/>
            <RowDefinition Height="93"/>
        </Grid.RowDefinitions>
        <Grid.ColumnDefinitions>
            <ColumnDefinition Width="*"/>
            <ColumnDefinition Width="295"/>
            <ColumnDefinition Width="*"/>
        </Grid.ColumnDefinitions>
        <Rectangle Fill="#FFF4F4F5" HorizontalAlignment="Left" Height="93" Stroke="Black" VerticalAlignment="Top" Width="792" Grid.ColumnSpan="3" Grid.Row="2" StrokeThickness="0"/>
        <Button Content="Назад" HorizontalAlignment="Left" Margin="60,41,0,0" VerticalAlignment="Top" Width="115" Height="32"/>
        <Frame x:Name="MainFrame" Source="Pages/AuthPage.xaml" HorizontalAlignment="Left" Height="307" VerticalAlignment="Top" Width="736" Grid.ColumnSpan="3" Margin="22,88,0,0" Grid.RowSpan="3"/>

    </Grid>
</Window>