<ComboBox>
    <CheckBox Content="SAW" IsChecked="{Binding Path=CurWeldingProcess, Converter={StaticResource wpFlagValueConverter}, ConverterParameter={x:Static models:WeldingProcess.SAW}}" />
    <CheckBox Content="FCAW" IsChecked="{Binding Path=CurWeldingProcess, Converter={StaticResource wpFlagValueConverter}, ConverterParameter={x:Static models:WeldingProcess.FCAW}}" />
    <CheckBox Content="SMAW" IsChecked="{Binding Path=CurWeldingProcess, Converter={StaticResource wpFlagValueConverter}, ConverterParameter={x:Static models:WeldingProcess.SMAW}}" />
</ComboBox>

public class WeldingProcessFlagValueConverter : IValueConverter
{
    private WeldingProcess target;

    public object Convert(object value, Type targetType, object parameter, CultureInfo culture)
    {
        WeldingProcess mask = (WeldingProcess)parameter;
        this.target = (WeldingProcess)value;
        return ((mask & this.target) != 0);
    }

    public object ConvertBack(object value, Type targetType, object parameter, CultureInfo culture)
    {
        this.target ^= (WeldingProcess)parameter;
        return this.target;
    }
}