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POOnline-Offline Class Manager
 

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    <p>Ok, first I'll describe my <strong>goal</strong>, then what I've <strong>coded</strong>, finally <strong>questions</strong>.</p> <h2>Goal</h2> <p>To have a <strong>generic class</strong> that manage multiple <em>contracts</em> that , and is able to find out wheter it's an online or offline situation, on the very moment when an operation is being made. There's a really easy way of doing it: a class for each Online-Offline pair that implement the contract and check on every each method wheter if it's online or not, and makes the right call. And that's exactly what I want to avoid.</p> <p>Just FYI, behind the scenes it would be an <em>Online scenario</em> connected to <strong>WCF services</strong> and an <em>Offline scenario</em> connected to a <strong>client local database</strong>.</p> <p>FYI 2: I've tried to accomplish this avoiding Interception and AOP stuff, but I found a dead end. You can see <a href="https://stackoverflow.com/questions/12395778/how-to-code-a-good-offline-online-dispatcher"><strong>this post</strong></a> where I implement what seems to be a good solution, but stablishes if it's connected or not on the <em>contructor</em>, but real-world scenario needs this check at <em>Operation level</em>, not <em>constructor level</em>.</p> <h2>Code</h2> <p>It's ready to run &amp; test: just copy/paste on a new console application.</p> <pre><code>using System; using System.Reflection; using Microsoft.Practices.Unity; using Microsoft.Practices.Unity.InterceptionExtension; namespace ConsoleApplication1 { public class Unity { public static IUnityContainer Container; public static void Initialize() { Container = new UnityContainer(); Container.AddNewExtension&lt;Interception&gt;(); Container.RegisterType&lt;ILogger, OnlineLogger&gt;(); Container.Configure&lt;Interception&gt;().SetInterceptorFor&lt;ILogger&gt;(new InterfaceInterceptor()); } } class Program { static void Main(string[] args) { Unity.Initialize(); var r = new Router&lt;ILogger, OnlineLogger, OfflineLogger&gt;(); try { r.Logger.Write("Method executed."); } catch (CantLogException ex) { r.ManageCantLogException(ex); } Console.ReadKey(); } } public class Router&lt;TContract, TOnline, TOffline&gt; where TOnline : TContract, new() where TOffline : TContract, new() { public TContract Logger; public Router() { Logger = Unity.Container.Resolve&lt;TContract&gt;(); } public void ManageCantLogException(CantLogException ex) { // Is this an ugly trick? I mean, the type was already registered with online. Unity.Container.RegisterType&lt;TContract, TOffline&gt;(); Logger = Unity.Container.Resolve&lt;TContract&gt;(); var method = ((MethodBase)ex.MethodBase); method.Invoke(Logger, ex.ParameterCollection); } } public interface ILogger { [Test] void Write(string message); } public class OnlineLogger : ILogger { public static bool IsOnline() { // A routine that check connectivity return false; // Should I perform a "lock" here to make this tread safe? } public void Write(string message) { Console.WriteLine("Logger: " + message); } } public class OfflineLogger : ILogger { public void Write(string message) { Console.WriteLine("Logger: " + message); } } [System.Diagnostics.DebuggerStepThroughAttribute()] public class TestAttribute : HandlerAttribute { public override ICallHandler CreateHandler(IUnityContainer container) { return new TestHandler(); } } public class TestHandler : ICallHandler { public int Order { get; set; } public IMethodReturn Invoke(IMethodInvocation input, GetNextHandlerDelegate getNext) { Console.WriteLine("It's been intercepted."); if (!OnlineLogger.IsOnline() &amp;&amp; input.Target is OnlineLogger) { Console.WriteLine("It's been canceled."); throw new CantLogException(input.MethodBase, input.Inputs); } return getNext()(input, getNext); } } public class CantLogException : Exception { public MethodBase MethodBase { get; set; } public object[] ParameterCollection { get; set; } public CantLogException(string message) : base(message) { } public CantLogException(MethodBase methodBase, IParameterCollection parameterCollection) { this.MethodBase = methodBase; var parameters = new object[parameterCollection.Count]; int i = 0; foreach (var parameter in parameterCollection) { parameters[i] = parameter; i++; } this.ParameterCollection = parameters; } } } </code></pre> <h2>Questions</h2> <ol> <li><p>Is this design that I present thread-safe?</p></li> <li><p>Is it a performance disgrace? The exception handling the Online-Offline situation and reflection there makes me fell I'm doing all wrong.</p></li> <li><p>I think this is a common requeriment, isn't there any api/fwk/whatever that does this Online-Offline management? Kind of feel like I'm reinventing the weel here.</p></li> <li><p>This is a long shot question: I really don't want client (<strong>Program</strong> class on this example) to know about the exception, isn't there any other way to <strong>cancel</strong> method execution but through an exception on the interceptor? Any other approach is welcomed too.</p></li> </ol> <hr> <p>I'm not interested on paid third-party stuff, so sadly things like <a href="http://www.sharpcrafters.com/" rel="nofollow noreferrer"><strong>PostSharp</strong></a> aren't options for me.</p>
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    1. COI wouldn't think *Chuck Norris* would have any problems with threads; Don't they synchronize themselves at your request? ;)
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    2. COmight be suitable for migration to [CodeReview.se]
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    3. COFirst I'll give it a shot here, since questions imply not only a *code review*, but conceptual level situations and maybe a complete refactor. If I don't get it answered here, I'll try [Code Review](http://codereview.stackexchange.com/). Thanks @codesparkle
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