exam_prepare/Windows/Auth.xaml

<Window x:Class="examPrepare.Windows.Auth"
        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:examPrepare.Windows"
        mc:Ignorable="d"
        Title="Auth" Height="450" Width="800">
  <StackPanel>
    <TextBox x:Name="login" Height="30" Width="140" />
    <TextBox x:Name="password" Height="30" Width="140" />
    <Button Content="Log in" Click="Button_Click" Width="140"/>
  </StackPanel>
</Window>