buechermarkt/BuechermarktClient/MainWindow.xaml

<Window x:Class="BuechermarktClient.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:BuechermarktClient"
        mc:Ignorable="d"
        Title="Buechermarkt" Height="350" Width="525" Loaded="Window_Loaded">
    <Grid>
        <Grid.ColumnDefinitions>
            <ColumnDefinition Width="Auto"/>
            <ColumnDefinition Width="Auto"/>
            <ColumnDefinition Width="Auto"/>
            <ColumnDefinition Width="Auto"/>
        </Grid.ColumnDefinitions>
        <Grid.RowDefinitions>
            <RowDefinition Height="Auto"/>
            <RowDefinition Height="Auto"/>
        </Grid.RowDefinitions>
        <Button Grid.Column="0" Content="Buchtypen" HorizontalAlignment="Left" Height="75" Margin="10,10,0,0" VerticalAlignment="Top" Width="100" Click="BookTypes_Click"/>
        <Button Grid.Column="1" Content="Schüler" HorizontalAlignment="Left" Height="75" Margin="10,10,0,0" VerticalAlignment="Top" Width="100" Click="Students_Click"/>
        <Button Grid.Column="2" Content="Bücher" HorizontalAlignment="Left" Height="75" Margin="10,10,0,0" VerticalAlignment="Top" Width="100" Click="Books_Click"/>
        <Button Grid.Column="3" Content="Verkauf" HorizontalAlignment="Left" Height="75" Margin="10,10,0,0" VerticalAlignment="Top" Width="100" Click="Sell_Click"/>
        <Button Grid.Column="0" Grid.Row="1" Content="Rechnungen" HorizontalAlignment="Left" Height="75" Margin="10,10,0,0" VerticalAlignment="Top" Width="100" Click="Bills_Click"/>
    </Grid>
</Window>