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POSimple ThreadSafe Log Class
 

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    <ol> <li><p>I'm wondering if I've used these components all correctly/efficiently. Specifically writing to files I'm not sure is thread-safe though it didn't throw any errors in this test project (even with no sleeping). I can't tell if this is because the broadcaster is already synchronized and therefore file-writes are subsequently synchronized as well... ?</p></li> <li><p>I wasn't sure if I could use a normal List&lt;> or some other collection instead of the BlockingCollection&lt;> for the <code>m_listeners</code>. I can add listeners cleanly enough at the start of execution, but I think I've limited myself if I want to remove them later. I may for example want to add/remove listeners more dynamically in the future such as adding a TextBox listener on showing a child form and removing it on closing.</p></li> </ol> <p>WindowsFormsApplication1 containing:</p> <ul> <li>Form1, register OnLoad event</li> <li>button1, register OnClick event</li> <li>button2, register OnClick event</li> <li>textbox1, enable multiline property and expand to show several lines at a time</li> </ul> <pre class="lang-cs prettyprint-override"><code>using System; using System.Collections.Generic; using System.ComponentModel; using System.Data; using System.Drawing; using System.Linq; using System.Text; using System.Windows.Forms; using System.Threading; using System.Threading.Tasks; using System.Collections.Concurrent; using System.IO; namespace WindowsFormsApplication1 { public partial class Form1 : Form { //Fields private volatile bool cancel1 = false; private volatile bool cancel2 = false; private volatile bool cancel3 = false; private volatile bool cancel4 = false; public Form1() { InitializeComponent(); } //Event Handlers private void button1_Click(object sender, EventArgs e) { //Automated Producers if (!cancel1) { Task.Factory.StartNew(() =&gt; { int count = 0; while (!cancel1) { Log.Append("File", "log to file " + count++); Thread.Sleep(1); } cancel1 = false; }); } if (!cancel2) { Task.Factory.StartNew(() =&gt; { int count = 0; while (!cancel2) { Log.Append("GUI", "log to GUI " + count++); Thread.Sleep(2); } cancel2 = false; }); } if (!cancel3) { Task.Factory.StartNew(() =&gt; { int count = 0; while (!cancel3) { Log.Append("Error", "log to Error " + count++); Thread.Sleep(3); } cancel3 = false; }); } if (!cancel4) { Task.Factory.StartNew(() =&gt; { int count = 0; while (!cancel4) { Log.Append("", "log to console " + count++); Thread.Sleep(4); } cancel4 = false; }); } } private void button2_Click(object sender, EventArgs e) { //Cancel Producers cancel1 = true; cancel2 = true; cancel3 = true; cancel4 = true; } private void Form1_Load(object sender, EventArgs e) { //Delete Old Files string LogFile = Directory.GetCurrentDirectory() + "\\Log.txt"; if (File.Exists(LogFile)) File.Delete(LogFile); string VerboseLog = Directory.GetCurrentDirectory() + "\\VerboseLog.txt"; if (File.Exists(VerboseLog)) File.Delete(VerboseLog); //Add Consumer Callback methods to Logger class //Append to File Log.RegisterWriter( new Action&lt;string, string&gt;((tag, entry) =&gt; { if (tag == "File") { using (TextWriter Stream = new StreamWriter(LogFile, true)) { Stream.WriteLine(entry); } } })); //Append to different file Log.RegisterWriter( new Action&lt;string, string&gt;((tag, entry) =&gt; { using (TextWriter Stream = new StreamWriter(VerboseLog, true)) { Stream.WriteLine(DateTime.Now + ":\t" + entry); } })); //Append to Console Log.RegisterWriter( new Action&lt;string, string&gt;((tag, entry) =&gt; { Console.WriteLine(entry); })); //Append to multiline textBox1 Log.RegisterWriter( new Action&lt;string, string&gt;((tag, entry) =&gt; { if (tag == "GUI") { entry += "\r\n"; if (this.InvokeRequired) { this.BeginInvoke(new Action&lt;string&gt;(textBox1.AppendText), new object[] { entry }); return; } else { //Under the circumstances, this never occurs. An invoke is always required. textBox1.AppendText(entry); return; } } })); } } public static class Log { //Fields private static BlockingCollection&lt;Tuple&lt;string, string&gt;&gt; m_logItems; private static BlockingCollection&lt;Action&lt;string, string&gt;&gt; m_listeners; //Methods public static void Append(string p_tag, string p_text) { //Add Log Entry m_logItems.Add(new Tuple&lt;string, string&gt;(p_tag, p_text)); } public static void RegisterWriter(Action&lt;string, string&gt; p_callback) { //Add callback method to list m_listeners.Add(p_callback); } //Constructor static Log() { //Init Blocking Lists m_listeners = new BlockingCollection&lt;Action&lt;string, string&gt;&gt;(); m_logItems = new BlockingCollection&lt;Tuple&lt;string, string&gt;&gt;(); //Begin Log Entry Consumer Task Task.Factory.StartNew(() =&gt; { //Consume as Log Entries are added to the collection foreach (var logentry in m_logItems.GetConsumingEnumerable()) { //Broadcast to each listener foreach (var callback in m_listeners) { callback(logentry.Item1, logentry.Item2); } } }); } } } </code></pre> <p>I didn't want to use a third-party logging library (partially to understand these mechanisms better) and just wanted to create a very simple way to post items from pretty much anywhere in my code (any thread) to various outputs (files, textboxes, the console, etc.).</p> <p>The frequency of logging in the real application is much much slower than demonstrated here (i.e. it should never produce more than can be consumed under real-world conditions).</p>
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    1. COI have edited your title. Please see, "[Should questions include “tags” in their titles?](http://meta.stackexchange.com/questions/19190/)", where the consensus is "no, they should not".
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      1. USJohn Saunders
    2. COWhat is your question? *"Is my code correct"*? If yes, I don't think it fits well to SO.
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    3. CONo, my questions are 1. is the FileWriter synchronized/threadsafe and 2. is there something better than using BlockingCollection for the m_listener object so that I can safely add/remove listeners/consumers to the collection.
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