如何使用WPF从用户输入绘制矩形

<Window x:Class="WpfApp.MainWindow"
        xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
        Title="WPF Draw Rectangle" Height="450" Width="800">
    <Grid>
        <Canvas x:Name="DrawingCanvas" MouseDown="DrawingCanvas_MouseDown" MouseMove="DrawingCanvas_MouseMove" MouseUp="DrawingCanvas_MouseUp" Background="White"/>
    </Grid>
</Window>

using Microsoft.Win32;
using System.Windows;
using System.Windows.Controls;
using System.Windows.Input;
using System.Windows.Media;

namespace WpfApp
{
    public partial class MainWindow : Window
    {
        private Point startPoint;
        private Rectangle currentRectangle;

        public MainWindow()
        {
            InitializeComponent();
        }

        private void DrawingCanvas_MouseDown(object sender, MouseButtonEventArgs e)
        {
            startPoint = e.GetPosition(DrawingCanvas);
            currentRectangle = new Rectangle
            {
                Stroke = Brushes.Black,
                StrokeThickness = 2
            };
            Canvas.SetLeft(currentRectangle, startPoint.X);
            Canvas.SetTop(currentRectangle, startPoint.Y);
            DrawingCanvas.Children.Add(currentRectangle);
        }

        private void DrawingCanvas_MouseMove(object sender, MouseEventArgs e)
        {
            if (e.LeftButton == MouseButtonState.Pressed && currentRectangle != null)
            {
                var endPoint = e.GetPosition(DrawingCanvas);
                currentRectangle.Width = Math.Abs(endPoint.X - startPoint.X);
                currentRectangle.Height = Math.Abs(endPoint.Y - startPoint.Y);
                Canvas.SetLeft(currentRectangle, Math.Min(startPoint.X, endPoint.X));
                Canvas.SetTop(currentRectangle, Math.Min(startPoint.Y, endPoint.Y));
            }
        }

        private void DrawingCanvas_MouseUp(object sender, MouseButtonEventArgs e)
        {
            currentRectangle = null;
        }
    }
}