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copied!<p>Before anything else, you should consider <strong>rethinking</strong> what your session object should be responsible for. Usually, when I see a <code>Commit</code> method, I look for a <code>Rollback</code> method also, to make sure that your updates are in some way consistent if an operation fails (although I am still not sure what the class is supposed to do).</p> <p>Also, if <code>Commit</code> commits transient data added by your <code>StoreSomething</code> methods, then I don't see why a "Session" (again, whatever that is) should be opened at all until you decide to actually commit.</p> <p>Adding a better description and some background to the problem might allow us to provide a better solution in the long term.</p> <p>Having said that, a slightly more refactored version might be:</p> <ol> <li><p><strong>Start by defining an interface first (<a href="http://en.wikipedia.org/wiki/Liskov_substitution_principle" rel="nofollow">Liskov Substitution Principle</a>):</strong></p> <pre><code>public interface IMySession { void StoreName(string name); void StoreAddress(string address); void Commit(); } </code></pre></li> <li><p><strong>Implement a simplest "plain old" session with basic functionality (<a href="http://en.wikipedia.org/wiki/Single_responsibility_principle" rel="nofollow">Single Responsibility Principle</a>):</strong></p> <pre><code>public class BasicSession : IMySession { #region IMySession members public void StoreName(string name) { // plain store } public void StoreAddress(string address) { // plain store } public void Commit() { // plain commit } #endregion } </code></pre></li> <li><p><strong>Finally, create a proxy class, which checks for timeouts, and forwards method calls to the base class:</strong></p> <pre><code>public class TimeLimitedSessionProxy : IMySession { private readonly IMySession _baseSession; private readonly TimeSpan _timeout; private DateTime _lastAccessedTime = DateTime.Now; public TimeLimitedSessionProxy(IMySession baseSession, TimeSpan timeout) { _baseSession = baseSession; _timeout = timeout; } #region IMySession members public void StoreName(string name) { IfNotTimedOut(() => _baseSession.StoreName(name)); } public void StoreAddress(string address) { IfNotTimedOut(() => _baseSession.StoreAddress(address)); } public void Commit() { IfNotTimedOut(() => _baseSession.Commit()); } #endregion private void IfNotTimedOut(Action action) { if (DateTime.Now - _lastAccessedTime > _timeout) { throw new TimeoutException("session timed out"); } action(); _lastAccessedTime = DateTime.Now; } } </code></pre></li> </ol> <p><strong>Overall result:</strong></p> <ul> <li><p>Other parts of your code should accept an <code>IMySession</code> object, not caring how it's actually implemented under the hood.</p></li> <li><p>Even the <code>TimeLimitedSessionProxy</code> accepts an <code>IMySession</code> and is ignorant about the actual implementation; all it cares about is timing.</p></li> <li><p>If you decide to add other functionality, consider leaving these classes intact and <a href="http://en.wikipedia.org/wiki/Proxy_pattern" rel="nofollow">proxying</a> or <a href="http://en.wikipedia.org/wiki/Decorator_pattern" rel="nofollow">decorating</a> them as needed.</p></li> </ul>

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