Slice/Cashier/StartWorkPage.xaml

<Page x:Class="Cashier.StartWorkPage"
      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:Cashier"
      mc:Ignorable="d" 
      d:DesignHeight="450" d:DesignWidth="800"
      Title="Начало работы">

    <Grid>
        <Grid.RowDefinitions>
            <RowDefinition Height="3*"/>
            <RowDefinition/>
            <RowDefinition/>
            <RowDefinition/>
            <RowDefinition/>
            <RowDefinition Height="3*"/>
        </Grid.RowDefinitions>
        <Grid.ColumnDefinitions>
            <ColumnDefinition/>
            <ColumnDefinition/>
        </Grid.ColumnDefinitions>
        <TextBlock HorizontalAlignment="Right" Grid.Row="1" VerticalAlignment="Center" Margin="5">ID магазина</TextBlock>
        <TextBox Grid.Row="1" Grid.Column="1" x:Name="TxtIDStore"  Margin="7,5,300,5"/>
        <TextBlock HorizontalAlignment="Right" Grid.Row="2" VerticalAlignment="Center" Margin="5">Номер кассы</TextBlock>
        <TextBox Grid.Row="2" Grid.Column="1" x:Name="TxtNumberCashier"  Margin="7,5,300,5"/>
        <TextBlock HorizontalAlignment="Right" Grid.Row="3" VerticalAlignment="Center" Margin="5">Код сотрудника</TextBlock>
        <TextBox Grid.Row="3" Grid.Column="1" x:Name="TxtCodeEmployee"  Margin="7,5,300,5"/>
        <Button Grid.Row="4" Grid.ColumnSpan="2" Height="30" Margin="300,0,300,0" Name="BtnConnect" Click="BtnConnect_Click">Начать</Button>
    </Grid>
</Page>