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POUnity WPF window lifetime manager
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  1. POUnity WPF window lifetime manager
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    copied!<p>I am using Unity as the DI container in my c# / WPF / NHibernate application.</p> <p>I want to use a custom lifetime manager that will give me a separate NHibernate session per WPF window. The Session returned by the container should be the session for the currently active window.</p> <p>The problem is, I can't get it to work. The container appears to create a new session at each request and then attempt to store this with the lifetime manager, rather than requesting the session from the lifetime manager first.</p> <p>This is the code for my custom lifetime manager:</p> <pre><code>class ActiveWindowLifetimeManager : LifetimeManager { private SynchronizationContext _uiContext; private ICacheFactory _cacheFactory; private ICache&lt;Window, ICache&lt;Guid, object&gt;&gt; _data; private Guid _key; public ActiveWindowLifetimeManager(ICacheFactory cacheFactory, SynchronizationContext uiContext, ICache&lt;Window, ICache&lt;Guid, object&gt;&gt; cache) { _key = Guid.NewGuid(); _uiContext = uiContext; _cacheFactory = cacheFactory; _data = cache; } public override object GetValue() { object result = null; _uiContext.Send(InternalGetValue, result); return result; } public override void SetValue(object newValue) { _uiContext.Send(InternalSetValue, newValue); } public override void RemoveValue() { _uiContext.Send(InternalRemoveValue, null); } // Note - I don't think we need to worry about concurrency issues as everything // is marshalled to the UI thread anyway private void InternalGetValue(object state) { ICache&lt;Guid, object&gt; cache = GetActiveWindowCache(); if (cache != null) { state = cache.Get(_key); } } private void InternalSetValue(object state) { ICache&lt;Guid, object&gt; cache = GetActiveWindowCache(); if (cache != null) { if (cache.Get(_key) == null) { cache.Add(_key, state); } } } private void InternalRemoveValue(object state) { ICache&lt;Guid, object&gt; cache = GetActiveWindowCache(); if (cache != null) { cache.Remove(_key); } } private ICache&lt;Guid, object&gt; GetActiveWindowCache() { ICache&lt;Guid, object&gt; result = null; Window activeWindow = Application.Current.Windows.OfType&lt;Window&gt;().FirstOrDefault(x =&gt; x.IsActive); if (activeWindow == null) { activeWindow = Application.Current.Windows.OfType&lt;Window&gt;().FirstOrDefault(); } if (activeWindow != null) { result = _data.Get(activeWindow); if (result == null) { result = _cacheFactory.GetCache&lt;Guid, object&gt;(100); _data.Add(activeWindow, result); } } return result; } } </code></pre> <p>There are three relevant registrations with the container. The first is the <code>ISession</code>, using the custom lifetime manager. the <code>INHSessionProvider</code> and <code>SessionProviderParameters</code> resolve without any problems.</p> <pre><code>container.RegisterType&lt;ISession&gt;("mainDBSession", container.Resolve&lt;ActiveWindowLifetimeManager&gt;(), new InjectionFactory(c =&gt; { SessionProviderParameters parameters = c.Resolve&lt;SessionProviderParameters&gt;("mainDBSessionProviderParams"); return c.Resolve&lt;INHSessionProvider&gt;(new ParameterOverride("parameters", parameters)).Session; })); </code></pre> <p>The next registers <code>INHUnitOfWork</code>, which is populated with an <code>ISession</code> from the above registration.</p> <pre><code>container.RegisterType&lt;INHUnitOfWork&gt;("mainDBUoW", new InjectionFactory(c =&gt; { return c.Resolve&lt;NHUnitOfWork&gt;(new ParameterOverride("session", c.Resolve&lt;ISession&gt;("mainDBSession"))); })); </code></pre> <p>Finally, the <code>Func&lt;INHUnitOfWork&gt;</code> is the dependency of any actual data access classes.</p> <pre><code>container.RegisterType&lt;Func&lt;INHUnitOfWork&gt;&gt;("mainDBUoWFactory", new InjectionFactory(f =&gt; new Func&lt;INHUnitOfWork&gt;(() =&gt; f.Resolve&lt;INHUnitOfWork&gt;("mainDBUoW")))); </code></pre> <p>I put a break point on my first data access statement and this is what hits <code>ActiveWindowLifetimeManager</code>:</p> <ol> <li>GetValue - lifetime manager key - {ca896ad2-1968-4bc7-94c6-ab2cb0ab08c2} - return null</li> <li>SetValue - lifetime manager key - {ca896ad2-1968-4bc7-94c6-ab2cb0ab08c2} - ISession hash code - 21438532</li> <li>GetValue - lifetime manager key - {ca896ad2-1968-4bc7-94c6-ab2cb0ab08c2} - return ISession hash code - 21438532</li> </ol> <p>At this point, <code>Func&lt;INHUnitOfWork&gt;</code> has returned and the actual session in the supplied <code>INHUnitOfWork</code> has hash code 21438532.</p> <p>I then hit my second data access statement and this is what hits <code>ActiveWindowLifetimeManager</code>:</p> <ol> <li>SetValue - lifetime manager key - {ca896ad2-1968-4bc7-94c6-ab2cb0ab08c2} - ISession hash code - 21320198</li> <li>GetValue - lifetime manager key - {ca896ad2-1968-4bc7-94c6-ab2cb0ab08c2} - return ISession hash code - 21438532</li> </ol> <p>Actual session in the supplied <code>INHUnitOfWork</code> has hash code 21320198 i.e. The container seems to have created a new session first and updated the lifetime manager in 1. The session returned by call 2 appears to be ignored.</p>
 

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