Why when using WebClient inside a backgroundworker it's still freezing the program untill the download is over ?

Question

In form1 constructor:
fileDownloadRadar();backgroundWorker2.RunWorkerAsync();
First i'm downloading one image from another source using WebClient in form1:
private void fileDownloadRadar()
if (Client.IsBusy == true)
Client.CancelAsync();
else
Client.DownloadFileAsync(myUri, combinedTemp);
Then in the DoWork event:
private void backgroundWorker2_DoWork(object sender, DoWorkEventArgs e)
SatelliteImages.ExtractCountires();
this.BeginInvoke(new MethodInvoker(delegate
for (int i = 0; i < SatelliteImages.countriescodes.Count; i++)
comboBox1.Items.Add(SatelliteImages.countriescodes[i]);
for (int i = 0; i < SatelliteImages.countriesnames.Count; i++)
comboBox2.Items.Add(SatelliteImages.countriesnames[i]);
comboBox1.Text = "is";
comboBox2.Text = "Europe";
SatelliteImages.ExtractDateTime(comboBox1.Text, true, combinedsatelliteimagesdir);
This is the SatelliteImages class:
using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Windows.Forms;
using System.Web;
using System.Globalization;
using System.IO;
using System.Net;
using System.Text.RegularExpressions;
namespace mws
public partial class SatelliteImages : Form
static WebClient client;
List<string> imagesUrls = new List<string>();
static string htmltoextract;
static string link;
static string text;
public static List<string> countriescodes = new List<string>();
public static List<string> countriesnames = new List<string>();
public SatelliteImages()
InitializeComponent();
public static void ExtractCountires()
htmltoextract = "http://sat24.com/en/?ir=true";//"http://sat24.com/en/";// + regions;
client = new WebClient();
client.DownloadFile(htmltoextract, @"c:\temp\sat24.html");
client.Dispose();
string tag1 = "<li><a href=\"/en/";
string tag2 = "</a></li>";
string s = System.IO.File.ReadAllText(@"c:\temp\sat24.html");
s = s.Substring(s.IndexOf(tag1));
s = s.Substring(0, s.LastIndexOf(tag2) + tag2.ToCharArray().Length);
s = s.Replace("\r", "").Replace("\n", "").Replace(" ", "");
string[] parts = s.Split(new string[] { tag1, tag2 }, StringSplitOptions.RemoveEmptyEntries);
string tag3 = "<li><ahref=\"/en/";
for (int i = 0; i < parts.Length; i++)
if (i == 17)
break;
string l = "";
if (parts[i].Contains(tag3))
l = parts[i].Replace(tag3, "");
string z1 = l.Substring(0, l.IndexOf('"'));
countriescodes.Add(z1);
string z2 = parts[i].Substring(parts[i].LastIndexOf('>') + 1);
countriesnames.Add(z2);
public static void ExtractDateTime(string selectedregion,bool infraredorvisual, string satimagesdir)
WebClient client1 = new WebClient();
string[] Urls = new string[9];
string input = File.ReadAllText(@"c:\temp\sat24.html");
string pattern1 = @"imageUrls = \[[^\]]*\]";
Regex ex1 = new Regex(pattern1, RegexOptions.Singleline);
string pattern2 = @"region=(?'region'[^&]*)&time=(?'time'\d{12})";
Match match1 = ex1.Match(input);
Regex ex2 = new Regex(pattern2, RegexOptions.Singleline);
MatchCollection matches2 = ex2.Matches(match1.Value);
IFormatProvider provider = CultureInfo.InvariantCulture;
List<DateTime> dateTime = new List<DateTime>();
foreach (Match match2 in matches2)
string region = match2.Groups["region"].Value;
DateTime dt = DateTime.ParseExact(match2.Groups["time"].Value, "yyyyMMddHHmm", provider);
switch (region)
case "eu":
dt.AddHours(1);
break;
case "is":
dt.AddHours(-1);
break;
dateTime.Add(dt);
for (int i = 0; i < dateTime.Count; i++)
string result = dateTime[i].ToString("yyyyMMddHHmm");
link = "http://www.sat24.com/image2.ashx?region=" + selectedregion + "&time=" + result + "&ir=" +
infraredorvisual ;
// why downloading so slow ? to check maybe to ask
// in forums.
string filePath = Path.Combine(satimagesdir, "SatImage" + i + ".GIF");
try
client1.DownloadFile(link, filePath);
catch (Exception e)
DannyGeneral.Logger.Write(e.ToString());
client1.Dispose();
private void SatelliteImages_Load(object sender, EventArgs e)
I guess the problem is in the SatelliteImages class where i'm downloading there first time the html file and then downloading 9 images.
I tried to start the backgroundworker2 inside the completed event in form1 of the WebClient.
But again it's all freezing untill it's completing downloading the images in the class SatelliteImages.
I thought put it in the backgroundworker2 dowork will not make it freeze.
Why the downloadings in the class SatelliteImages make it all freeze untill it finish the downloadings even if it's inside the backgroundworker2 dowork event ?

Answer 1

Unless I have missed something, the only thing that is running on the background thread is:
SatelliteImages.ExtractCountires();
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