WPF canvas draw lines via brush

//xaml
<Window x:Class="WpfApp11.MainWindow"
        xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
        xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
        xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
        xmlns:local="clr-namespace:WpfApp11"
        mc:Ignorable="d" WindowState="Maximized"
        Title="MainWindow" Height="450" Width="800">
    <Grid>
        <Canvas Background="White" Name="cvs" MouseLeftButtonDown="cvs_MouseLeftButtonDown"
                MouseMove="cvs_MouseMove" MouseUp="cvs_MouseUp"/>
    </Grid>
</Window>


//xaml.cs
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
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 WpfApp11
{
    /// <summary>
    /// Interaction logic for MainWindow.xaml
    /// </summary>
    public partial class MainWindow : Window
    {
        Point _pos;
        bool _isDrawing;
        Brush _stroke=Brushes.Black;
        public MainWindow()
        {
            InitializeComponent();
        }

        private void cvs_MouseLeftButtonDown(object sender, MouseButtonEventArgs e)
        {
            _isDrawing = true;
            _pos = e.GetPosition(cvs);
            cvs.CaptureMouse();
        }

        private void cvs_MouseMove(object sender, MouseEventArgs e)
        {
            if(_isDrawing)
            {
                Line line = new Line();
                line.X1 = _pos.X;
                line.Y1 = _pos.Y;
                _pos=e.GetPosition(cvs);
                line.X2 = _pos.X;
                line.Y2= _pos.Y;
                line.Stroke = _stroke;
                line.StrokeThickness = 10;
                cvs.Children.Add(line);
            }
        }         

        private void cvs_MouseUp(object sender, MouseButtonEventArgs e)
        {
            _isDrawing=false;
            cvs.ReleaseMouseCapture();
        }
    }
}