轴更换后如何使矩形尺寸不变

Question

我想制作在更换轴后不会缩放尺寸的矩形。 更改X和Y最小或最大值后，OxyPlot缩放矩形。 我不知道X和Y轴的“新”最小值和最大值。这是简单的方法吗？

    File path                       Existence
    C:\Users\Desktop\Excel\Jan15.txt    1
    C:\Users\Desktop\Excel\Feb15.txt    1
    C:\Users\Desktop\Excel\Mar15.txt    1
    C:\Users\Desktop\Excel\Apr15.txt    0
    C:\Users\Desktop\Excel\May15.txt    0

Xaml看起来像这样

using GalaSoft.MvvmLight.Command;
using OxyPlot;
using OxyPlot.Annotations;
using OxyPlot.Axes;
using OxyPlot.Series;
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Windows;
using System.Windows.Controls;
using System.Windows.Data;
using System.Windows.Documents;
using System.Windows.Input;
using System.Windows.Media;
using System.Windows.Media.Imaging;
using System.Windows.Navigation;
using System.Windows.Shapes;

namespace WpfApplication22
{
/// <summary>
/// Interaction logic for MainWindow.xaml
/// </summary>
public partial class MainWindow : Window
{
    public MainWindow()
    {
        InitializeComponent();
        DataContext = new PlotRectangle();
    }
}
public class PlotRectangle
{
    public ICommand ComboCommand { get; set; }
    public PlotModel PlotModel { get; set; }
    public LinearAxis XAxis { get; set; }
    public LinearAxis YAxis { get; set; }
    public LineSeries LineSeries { get; set; }
    public RectangleAnnotation Rect {get;set;}
    public List<string> Items { get; set; }
    public PlotRectangle()
    {
        ComboCommand = new RelayCommand(()=>ChangeAxis());
        PlotModel = new PlotModel();
        Rect = new RectangleAnnotation();
        LineSeries = new LineSeries();
        Items = new List<string>();
        Items.Add("5");
        Items.Add("10");
        Items.Add("15");

        Rect.MinimumX = 10;
        Rect.MaximumX = 20;
        Rect.MinimumY = 1;
        Rect.MaximumY = 10;
        XAxis = new LinearAxis
        {
            Position=AxisPosition.Bottom,
        };
        YAxis = new LinearAxis
        {
            Position = AxisPosition.Left
        };
        PlotModel.Axes.Add(XAxis);
        PlotModel.Axes.Add(YAxis);
        PlotModel.Series.Add(LineSeries);
        PlotModel.Annotations.Add(Rect);
    }
    public void ChangeAxis()
    {
        Random rnd1 = new Random();
        Random rnd2 = new Random();
        Random rnd3 = new Random();
        Random rnd4 = new Random();
        PlotModel.Axes[1] = new LinearAxis
        {
            Minimum=rnd1.Next(1,10),
            Maximum=rnd2.Next(15,50)
        };
        PlotModel.Axes[0] = new LinearAxis
        {
            Minimum = rnd3.Next(1, 10),
            Maximum = rnd4.Next(15, 50)
        };
        PlotModel.InvalidatePlot(true);
    }
}
}

我需要在屏幕上绘图，但是如何？