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 :).
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;
11
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;
17
18 public WinAppMain() {
19 InitializeComponent();
20 }
21
22 private void btnStart_Click(object sender, EventArgs e) {
23 btnStart.Enabled = false;
24 btnStop.Enabled = true;
25
26 InitializeList();
27 InitializeBar();
28 RunWorker();
29 }
30
31 //initilaize progress nar
32 private void InitializeBar() {
33 progressBar.Maximum = 100;
34 progressBar.Minimum = 0;
35 progressBar.Value = 0;
36 }
37
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 }
50
51 //create a new backround worker
52 private void RunWorker() {
53 worker = new BackgroundWorker();
54 worker.WorkerReportsProgress = true;
55 worker.WorkerSupportsCancellation = true;
56
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 }
62
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>;
67
68 for (int index = 0; index<= inputList.Count-1; index++) {
69 //do more work here
70 Thread.Sleep(1000);
71
72 int progressInPercent = (int)(((decimal)(index + 1)/(decimal)inputList.Count) * 100);
73 worker.ReportProgress(progressInPercent, inputList[index]);
74
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 }
83
84 //executed when worker was finished
85 private void worker_RunWorkerCompleted(object sender, RunWorkerCompletedEventArgs e) {
86 lblStatus.Text = "work finished processing request.";
87 }
88
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 }
94
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.";
99
100 btnStart.Enabled = true;
101 btnStop.Enabled = false;
102 }
103 }
104 }
You can also create multiple background workers running at the same time. HTH.