问缩放或填充后轴ActualMaximum和最大值不匹配(OxyPlot)

EN

public class OxyPlotModel : INotifyPropertyChanged
    {

        private OxyPlot.PlotModel plotModel;
        public OxyPlot.PlotModel PlotModel
        {
            get
            {
                return plotModel;
            }
            set
            {
                plotModel = value;
                OnPropertyChanged("PlotModel");
            }
        }

        public event PropertyChangedEventHandler PropertyChanged;
        protected void OnPropertyChanged(string name)
        {
            PropertyChangedEventHandler handler = PropertyChanged;
            if (handler != null)
            {
                handler(this, new PropertyChangedEventArgs(name));
            }
        }
    }

public MainWindow()
        {
            InitializeComponent();

            oxyPlotModel = new OxyPlotModel();
            oxyPlotModel.PlotModel = plotModel;
            plotView1.DataContext = oxyPlotModel;

            plotModel.Axes.Clear();

            var yAxis = new OxyPlot.Axes.LinearAxis();
            var xAxis = new OxyPlot.Axes.LinearAxis();
            xAxis.Position = OxyPlot.Axes.AxisPosition.Bottom;

            plotModel.Axes.Add(yAxis);
            plotModel.Axes.Add(xAxis);

            plotModel.Axes[1].Minimum = 0;
            plotModel.Axes[1].Maximum = 700;
        }

        private void button1_Click(object sender, RoutedEventArgs e)
        {
            plotModel.Axes[1].Minimum = 100;
            plotModel.Axes[1].Maximum = 500;
            Debug.Print(plotModel.Axes[1].MaximumPadding.ToString());
            plotModel.InvalidatePlot(true);
        }