.NET: Updated: Simple and Stupid BackgroundWorker Example

rdagumampan — Wed, 20 Jun 2007 14:36:00 GMT

I was very busy the past weeks, I cannot imagine I could make it not to code for several days, been a carpenter, janitor, messenger and everything hehe. But I'm here again now. Let me start this out with this stupid sample I just given to one of my junior developer.

BackgroundWorker is a special class in .NET 2.0 to help developers implement non-freezing UI, multi-threaded windows forms applications. It provides intuitive model for hanldling events, reporting progress, and notifying the user interface.

In my opinion, it is a must for all windows forms developers to know this and learn how to implement this. But the problem I can see is that, most of times junior developers dont know where to start and sometimes overwelemed by the documentations most websites and microsft provided. Lets keep it this simple :).

Instructions:

Create a new VS2005 C# Window Forms project.
Add a new Form, name it "WinAppMain".
On form add two buttons "btnStart" and "btnStop".
Add a label "lblStatus".
Add a progressbar control "progressBar".

Then review and implement this code, sorry but you cannot copy this hehe.

2 Description: very simple background worker sample

6 using System;

7 using System.Collections.Generic;

8 using System.ComponentModel;

9 using System.Threading;

10 using System.Windows.Forms;

12 namespace WindowAppEx {

13 public partial class WinAppMain : Form {

14 //class level variables

15 List<string> employees = new List<string>();

16 private BackgroundWorker worker = null;

18 public WinAppMain() {

19 InitializeComponent();

20 }

22 private void btnStart_Click(object sender, EventArgs e) {

23 btnStart.Enabled = false;

24 btnStop.Enabled = true;

26 InitializeList();

27 InitializeBar();

28 RunWorker();

29 }

31 //initilaize progress nar

32 private void InitializeBar() {

33 progressBar.Maximum = 100;

34 progressBar.Minimum = 0;

35 progressBar.Value = 0;

36 }

38 //create a dummy list, assume this is a list of employees to be processed on a backgroun thread

39 private void InitializeList() {

40 employees.Add("Marilyn Manalo");

41 employees.Add("Shereen Guinucud");

42 employees.Add("Eunice Hosmillo");

43 employees.Add("Haizel Lin");

44 employees.Add("Rizchelle Priagula");

45 employees.Add("Cyd Clarence Petalino");

46 employees.Add("June Aileen Fesariton");

47 employees.Add("Gwendale Gertrude Aranas ");

48 employees.Add("Juvy Viñas");

49 }

51 //create a new backround worker

52 private void RunWorker() {

53 worker = new BackgroundWorker();

54 worker.WorkerReportsProgress = true;

55 worker.WorkerSupportsCancellation = true;

57 worker.DoWork += new DoWorkEventHandler(worker_DoWork);

58 worker.RunWorkerCompleted += new RunWorkerCompletedEventHandler(worker_RunWorkerCompleted);

59 worker.ProgressChanged += new ProgressChangedEventHandler(worker_ProgressChanged);

60 worker.RunWorkerAsync(employees);

61 }

63 //begin working on files

64 private void worker_DoWork(object sender, DoWorkEventArgs e) {

65 BackgroundWorker senderWorker = sender as BackgroundWorker;

66 List<string> inputList = e.Argument as List<string>;

68 for (int index = 0; index<= inputList.Count-1; index++) {

69 //do more work here

70 Thread.Sleep(1000);

72 int progressInPercent = (int)(((decimal)(index + 1)/(decimal)inputList.Count) * 100);

73 worker.ReportProgress(progressInPercent, inputList[index]);

75 //handle cancellation of the thread, even CancelAsync was called, the worker is still processing request

76 //explict hanlding of cancellation is needed here to avoud null reference exception

77 if(senderWorker.CancellationPending) {

78 e.Cancel = true;

79 break;

80 }

81 }

82 }

84 //executed when worker was finished

85 private void worker_RunWorkerCompleted(object sender, RunWorkerCompletedEventArgs e) {

86 lblStatus.Text = "work finished processing request.";

87 }

89 //executed when worker finished processign one item

90 private void worker_ProgressChanged(object sender, ProgressChangedEventArgs e) {

91 progressBar.Value = e.ProgressPercentage;

92 lblStatus.Text = "working on file of: " + e.UserState;

93 }

95 //worker cancelled when cancel button was clicked

96 private void btnStop_Click(object sender, EventArgs e) {

97 worker.CancelAsync();

98 lblStatus.Text = "work was stopped.";

100 btnStart.Enabled = true;

101 btnStop.Enabled = false;

102 }

103 }

104 }

You can also create multiple background workers running at the same time. HTH.

.NET: Unable to load one or more of the requested types exception in winforms

rdagumampan — Fri, 24 Nov 2006 19:52:00 GMT

I have encoutered this very strange error when Im trying to modify one of my user controls on a winddows forms module. It's the first happened to me so I assume I can fix this just by cleaning up the bin folder, update references, reload or restart the project. To no avail, I have googled around and I found this thread.

a hotfix is available at MSDN website. But there's one big problem with this hotfix, I cannot download it! It requires me to install MS File Transfer Manager active x control, what the... I tried everything on my IE settings to enable it but still I cannot install the activex, even the options to install on top of page is not available. Dont try downloading this on firefox, it will just download the aspx page.

I felt really frustrated with this hotfix because I need it badly, i googled around again and voila I founda a link to download the MS FTM windows client here. bad bad badd....

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L10N: Autosize property of labels on windows forms

rdagumampan — Tue, 07 Nov 2006 17:24:00 GMT

Lately, I was wondering why the Autosize property of label on windows forms is set to true, this is annoying and tiring if you love using windows forms designer(yucks! kidding ), because you often want a properly aligned controls and fixed with labels on data entry textboxes.But not until i want to loicalize these labels I realized that this is very helpful on making labels display localized text that extends more than the default text. Most of the time, English text is shorter than dannish, finnish, or scadinavian translations, sometimes its the other way around.

HTH!

Rodel E. Dagumampan : windows forms

.NET: Updated: Simple and Stupid BackgroundWorker Example

.NET: Unable to load one or more of the requested types exception in winforms

L10N: Autosize property of labels on windows forms