Asynchronous Image Loading in Xamarin Android

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:minWidth="25px"
    android:minHeight="25px"
    android:layout_width="fill_parent"
    android:layout_height="fill_parent"
    android:gravity="center_horizontal"
    android:orientation="vertical">
 
    <Button
        android:text="Download Image"
        android:id="@+id/downloadButton"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content" />
 
    <LinearLayout
        android:minWidth="25px"
        android:minHeight="25px"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:orientation="horizontal"
        android:id="@+id/progressLayout"
        android:gravity="center">
 
        <ProgressBar
            android:layout_width="wrap_content"
            android:layout_height="match_parent"
            android:id="@+id/progressBar1" />
        <TextView
            android:text="Loading.."
            android:layout_width="wrap_content"
            android:layout_height="match_parent"
            android:id="@+id/textView1"
            android:gravity="center" />
    </LinearLayout>
 
    <ImageView
        android:src="@android:drawable/ic_menu_gallery"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:id="@+id/imageView1" />
</LinearLayout>

using System;
 
using Android.App;
using Android.Content;
using Android.Runtime;
using Android.Views;
using Android.Widget;
using Android.OS;
using Android.Graphics;
using System.Threading.Tasks;
using System.IO;
using System.Net;
 
namespace ImageViewExample
{
    [Activity (Label = "ImageViewExample", MainLauncher = true, Icon = "@drawable/icon")]
    public class MainActivity : Activity
    {
 
        Button downloadButton;
        ImageView imageView;
        LinearLayout progressLayout;
 
        //Instance of webclient for async processing
        WebClient webClient;
 
        protected override void OnCreate (Bundle bundle){
            base.OnCreate (bundle);
 
            // Set our view from the "main" layout resource
            SetContentView (Resource.Layout.Main);
 
            this.imageView = FindViewById<ImageView> (Resource.Id.imageView1);
            //Hide progressbar initially
            this.progressLayout = FindViewById<LinearLayout> (Resource.Id.progressLayout);
            this.progressLayout.Visibility = ViewStates.Gone;
 
            // Get views from the layout resource axml file
            this.downloadButton = FindViewById<Button> (Resource.Id.downloadButton);
            downloadButton.Click += downloadAsync;
        }
 
        async void downloadAsync(object sender, System.EventArgs ea){
                  //Logic to download image and display on ImageView
        }
 
        void cancelDownload(object sender, System.EventArgs ea){
                 // Logic to cancel downlaod
        }
    }
}

async void downloadAsync(object sender, System.EventArgs ea){
    webClient = new WebClient ();
    var url = new Uri ("http://doubletreebyhiltonsanjose.com/wp-content/uploads/2014/08/Dog-Pictures-1024x698.jpg");
    byte[] imageBytes = null;
 
    //Show loading progress
    this.progressLayout.Visibility = ViewStates.Visible;
 
    //Toggle button click listener to cancel the task
    this.downloadButton.Text = "Cancel Download";
    this.downloadButton.Click -= downloadAsync;
    this.downloadButton.Click += cancelDownload;
 
    try{
        imageBytes = await webClient.DownloadDataTaskAsync(url);
    } catch(TaskCanceledException){
        this.progressLayout.Visibility = ViewStates.Gone;
        return;
    } catch(Exception e){
        this.progressLayout.Visibility = ViewStates.Gone;
 
        this.downloadButton.Click -= cancelDownload;
        this.downloadButton.Click += downloadAsync;
        this.downloadButton.Text = "Download Image";
        return;
    }
 
    //Saving bitmap locally
    string documentsPath = System.Environment.GetFolderPath (System.Environment.SpecialFolder.Personal);
    string localFilename = "image.png";
    string localPath = System.IO.Path.Combine (documentsPath, localFilename);
 
    //Save the Image using writeAsync
    FileStream fs = new FileStream (localPath, FileMode.OpenOrCreate);
    await fs.WriteAsync (imageBytes, 0, imageBytes.Length);
    Console.WriteLine("Saving image in local path: "+localPath);
 
    //Close file connection
    fs.Close ();
 
    BitmapFactory.Options options = new BitmapFactory.Options ();
    options.InJustDecodeBounds = true;
    await BitmapFactory.DecodeFileAsync (localPath, options);
 
    //Resizing bitmap image
    options.InSampleSize = options.OutWidth > options.OutHeight ? options.OutHeight / imageView.Height : options.OutWidth / imageView.Width;
    options.InJustDecodeBounds = false;
 
    Bitmap bitmap = await BitmapFactory.DecodeFileAsync (localPath, options);
    imageView.SetImageBitmap (bitmap);
 
    //Hide progress bar layout
    this.progressLayout.Visibility = ViewStates.Gone;
 
    //Toggle button click listener
    this.downloadButton.Click -= cancelDownload;
    this.downloadButton.Click += downloadAsync;
    this.downloadButton.Text = "Download Image";
}

void cancelDownload(object sender, System.EventArgs ea){
    if(webClient!=null)
        webClient.CancelAsync ();
 
    //Hide progressbar layout
    this.progressLayout.Visibility = ViewStates.Gone;
 
    //Toggle button click listener
    this.downloadButton.Click -= cancelDownload;
    this.downloadButton.Click += downloadAsync;
    this.downloadButton.Text = "Download Image";
}