How to link combobox in designer with combobox in property?

How to link combobox in designer with combobox in property?
Binding ModelItem.Method like in ExpressionTextBox is not working.
Please, help me :disappointed_relieved:

<ComboBox x:Name="Method" Grid.Row="0" Grid.Column="1" HorizontalAlignment="Left" Margin="0,0,0,0" VerticalAlignment="Top" Width="130" ItemsSource="{Binding ModelItem.Method, ConverterParameter=In, Converter={StaticResource ArgumentToExpressionConverter}, Mode=TwoWay}">
    <ComboBoxItem Content="GET" />
    <ComboBoxItem IsSelected="True" Content="POST"/>
    <ComboBoxItem Content="PUT"/>
</ComboBox>