Sneakers/SneakersSkakunov/Add.xaml

<Page x:Class="SneakersSkakunov.Add"
      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:SneakersSkakunov"
      mc:Ignorable="d" 
      d:DesignHeight="720" d:DesignWidth="1080"
      Title="Add">

    <Grid Background="#f5f5f5">
        <Grid.RowDefinitions>
            <RowDefinition Height="*"></RowDefinition>
            <RowDefinition Height="60"></RowDefinition>
        </Grid.RowDefinitions>
        <StackPanel Grid.Row="0">
            <StackPanel>
                <TextBox Background="#0000" HorizontalAlignment="Center" FontSize="32" FontWeight="Bold" Foreground="#4f4f4f">Добавление ОСАГО</TextBox>

                <GroupBox Header="Введите номер ОСАГО" Margin="10,0,10,0">
                    <TextBox Name="NumberIns" Foreground="#4f4f4f"></TextBox>
                </GroupBox>

                <GroupBox Header="Введите дату конца действия ОСАГО" Margin="10,5,10,0">
                    <DatePicker Name="DataEndIns" Foreground="#4f4f4f"></DatePicker>
                </GroupBox>

                <GroupBox Header="Выберите автомобиль" Margin="10,5,10,0">
                    <ComboBox Name="Avto" Foreground="#4f4f4f"></ComboBox>
                </GroupBox>

                <GroupBox Header="Введите год выпуска автомобиля" Margin="10,5,10,0">
                    <ComboBox Name="YearAvto" Foreground="#4f4f4f"></ComboBox>
                </GroupBox>

                <GroupBox Header="Введите цвет автомобиля" Margin="10,5,10,0">
                    <ComboBox Name="AvtoColor" Foreground="#4f4f4f"></ComboBox>
                </GroupBox>
            </StackPanel>
        </StackPanel>
        <StackPanel Grid.Row="1" VerticalAlignment="Center" HorizontalAlignment="Left" Orientation="Horizontal" Margin="10">
            <Border BorderThickness="1" CornerRadius="4" BorderBrush="#292929" Background="White" Width="90" Height="20">
                <Button Background="#0000" BorderBrush="#0000" Foreground="#292929" Content="Вернуться" Click="Revert"></Button>
            </Border>
            <Border BorderThickness="1" CornerRadius="4" BorderBrush="#292929" Background="White" Width="90" Height="20" Margin="10,0,0,0">
                <Button Background="#0000" BorderBrush="#0000" Foreground="#292929" Content="Добавить" Name="BtnAdd"  ></Button>
            </Border>

        </StackPanel>
    </Grid>
</Page>