NewAuthAndCaptcha/AuthAndCaptcha/Views/Calculator.axaml

<UserControl xmlns="https://github.com/avaloniaui"
             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:vm="using:AuthAndCaptcha.ViewModels"
             mc:Ignorable="d" d:DesignWidth="800" d:DesignHeight="450"
             x:Class="AuthAndCaptcha.Calculator"
			 x:DataType="vm:MainWindowViewModel">
	
	<Grid>
		<StackPanel>
			<StackPanel Classes="calcOptionSP">
				<TextBlock>Выберите арифметическую операцию:</TextBlock>
				<StackPanel Classes="calcOptionSP">
					<ComboBox Classes="calcCB" ItemsSource="{Binding CalculatorVM.calcOptions}" SelectedItem="{Binding CalculatorVM.SelectedOption}">
					</ComboBox>
				</StackPanel>	
			</StackPanel>

			<StackPanel Classes="cellsForCalcSP">
				<TextBox Text="{Binding CalculatorVM.N}" Classes="cellsForCalcTB"></TextBox>
				<TextBlock Classes="calcSymTB" Text="{Binding CalculatorVM.Sign}"></TextBlock>
				<TextBox Text="{Binding CalculatorVM.M}" Classes="cellsForCalcTB"></TextBox>
			</StackPanel>
			<StackPanel Classes="calcOptionSP">
				<Button Classes="calcBut" Command="{Binding CalculatorVM.Calculation}">Вычислить</Button>
			</StackPanel>
			<StackPanel Classes="calcOptionSP">
				<TextBlock Text="Результат"></TextBlock>
				<TextBlock Text="{Binding CalculatorVM.Result}"></TextBlock>
			</StackPanel>
			
		</StackPanel>
	</Grid>
</UserControl>