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    <p>Some of the questions to consider are:</p> <ul> <li><p>Is your application multi-threaded? Is the thread[s] which write[s] the messages the same as the UI thread which reads the messages and populates the list box?</p></li> <li><p>How many messages per second and being created?</p></li> <li><p>How many times per second do you want to update the list box?</p></li> <li><p>What's the maximum number of messages over time? Do you display them all in the list box, or do you discard older ones?</p></li> <li><p>Do you want log the messages into a file as well (e.g. for tech support purposes)?</p></li> <li><p>Is the listbox (the UI element) the only place where messages are stored? Is the listbox always displayed, or can the user hide/destroy it?</p></li> <li><p>How sophisticated are the end-users? Can you ask them to use other (better) tools to view your log file, or do you need to implement a (relatively unsophisticated) viewer into your own UI?</p></li> </ul> <p>Sorry to answer your question with questions, but these are questions which need answering before you can say "is this the best approach?".</p> <hr> <blockquote> <p>it's not a multithreaded application, is a freaking small application that I don't want to overload.</p> </blockquote> <p>If the application isn't multi-threaded, then the 'simplest thing that could possibly work' would be to not bother with a list or queue; and instead, let your other classes append messages directly into the UI listbox element (perhaps via a delegate), for example:</p> <pre><code>class MyClass { Action&lt;string&gt; log; MyClass(Action&lt;string&gt; log) { this.log = log; } void Something() { //log a message log("Hello world!"); } } class MyForm { ListBox listBox = new ListBox(); MyClass myClass; MyForm() { //create a delegate which logs strings //by writing them to the ListBox Action&lt;string&gt; log = delegate(string s) { listBox.Items.Add(s); }; //pass this logger to classes which need to use it myClass = new MyClass(log); //test it myClass.Something(); } } </code></pre> <hr> <p>Here's similar code using a non-anonymous delegate, with some extra functionality as requested in one of your comments:</p> <pre><code>class MyForm { ListBox listBox = new ListBox(); MyClass myClass; MyForm() { //pass the Log action to classes which need to use it myClass = new MyClass(Log); //test it myClass.Something(); } ///logs strings by writing them to the ListBox void Log(string s) { if (listBox.Items.Count == 300) listBox.Items.RemoveAt(0); listBox.Items.Add(s); } } </code></pre> <hr> <blockquote> <p>I think I answer wrong the (6). I should be able to send messages even if the listbox has not been created yet... that's why I suggested a List or Queue</p> </blockquote> <p>In this case, you do need storage other than only the ListBox. Your suggestion would work. An alternative suggestion is:</p> <ul> <li>When you create your ListBox, populate it from the List (using the ListBox.Items.AddRange method)</li> <li>In the Log function, if the ListBox doesn't exist then write the message to the List, else if the ListBox does exist then write the message to the ListBox.</li> </ul> <p>Doing this <em>might</em> be (very slightly) simpler than defining, listening to, and firing an event.</p>
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    1. POWhat is the best approach to send some text from one class to another (with some restrictions)?
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    1. POWhat is the best approach to send some text from one class to another (with some restrictions)?
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    1. CO(1) Is not multitheaded (2) Could be 5 messages in a lapse of a second, then 40 minutes without messages, then 1 ... but they are not that frequent (3) I was thinking to update the listbox only when I receive a message (4) 300, if listbox.items>300 i discard the oldest (5) no
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    2. CO(6) yes, it's the only place and cannot be hide (7) They only need to view the listbox if the want to know what the application is doing, nothing more, nothing less.
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    3. COThanks!, mmm.. that seems like a better option of what i was suggesting, but I think I answer wrong the (6). I should be able to send messages even if the listbox has not been created yet... that's why I suggested a List<string> or Queue<string>
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