Cafe/Cafe2/ErrorWindow.xaml

<Window x:Class="Cafe.ErrorWindow"
        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:Cafe"
        mc:Ignorable="d"
        Title="Ошибка" Height="100" Width="400" WindowStartupLocation="CenterScreen" WindowStyle="None" ResizeMode="CanMinimize">
    <Grid>
        <Button x:Name="BackButton" Content="Назад" VerticalAlignment="Top" HorizontalAlignment="Center" Height="30" Width="130" Margin="0,57,0,0" Click="BackClick"/>
        <Label Name="Error" Content="Ошибка: " HorizontalAlignment="Center" Margin="0,18,0,0" VerticalAlignment="Top" Height="29" Width="354" Foreground="White"/>
    </Grid>
</Window>