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POIntermittent "Specified cast is invalid" with StructureMap injected data context
 

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  1. POIntermittent "Specified cast is invalid" with StructureMap injected data context
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    <p>I am intermittently getting an <code>System.InvalidCastException: Specified cast is not valid.</code> error in my repository layer when performing an abstracted <code>SELECT</code> query mapped with LINQ. </p> <p>The error can't be caused by a mismatched database schema since it works intermittently and it's on my local dev machine.</p> <p>Could it be because StructureMap is caching the data context between page requests? If so, how do I tell StructureMap v2.6.1 to inject a new data context argument into my repository for each request?</p> <p><strong>Update:</strong> I found <a href="https://stackoverflow.com/questions/318716/asp-net-mvc-iis6-error-on-high-traffic-specified-cast-is-not-valid">this question</a> which correlates my hunch that something was being re-used. Looks like I need to call Dispose on my injected data context. Not sure how I'm going to do this to <em>all</em> my repositories without copypasting a lot of code.</p> <p><strong>Edit</strong>: These errors are popping up all over the place whenever I refresh my local machine too quickly. Doesn't look like it's happening on my remote deployment box, but I can't be sure.</p> <p>I changed all my repositories' StructureMap life cycles to <code>HttpContextScoped()</code> and the error persists.</p> <h2>Code:</h2> <pre><code>public ActionResult Index() { // error happens here, which queries my page repository var page = _branchService.GetPage("welcome"); if (page != null) ViewData["Welcome"] = page.Body; ... } </code></pre> <h2>Repository:</h2> <p>GetPage boils down to a filtered query mapping in my page repository.</p> <pre><code>public IQueryable&lt;Page&gt; GetPages() { var pages = from p in _db.Pages let categories = GetPageCategories(p.PageId) let revisions = GetRevisions(p.PageId) select new Page { ID = p.PageId, UserID = p.UserId, Slug = p.Slug, Title = p.Title, Description = p.Description, Body = p.Text, Date = p.Date, IsPublished = p.IsPublished, Categories = new LazyList&lt;Category&gt;(categories), Revisions = new LazyList&lt;PageRevision&gt;(revisions) }; return pages; } </code></pre> <p>where _db is an injected data context as an argument, stored in a private variable which I reuse for SELECT queries.</p> <h2>Calling code:</h2> <pre><code>public Page GetPage(string slug) { return _pageRepository.GetPages() .WithSlug(slug).FirstOrDefault(); } </code></pre> <p><code>WithSlug</code> is just a pipeline filter that adds a where clause to the query.</p> <h2>Error:</h2> <pre><code>Specified cast is not valid. Exception Details: System.InvalidCastException: Specified cast is not valid. </code></pre> <h2>Stack Trace:</h2> <pre><code>[InvalidCastException: Specified cast is not valid.] System.Data.Linq.SqlClient.SqlProvider.Execute(Expression query, QueryInfo queryInfo, IObjectReaderFactory factory, Object[] parentArgs, Object[] userArgs, ICompiledSubQuery[] subQueries, Object lastResult) +4539 System.Data.Linq.SqlClient.SqlProvider.ExecuteAll(Expression query, QueryInfo[] queryInfos, IObjectReaderFactory factory, Object[] userArguments, ICompiledSubQuery[] subQueries) +207 System.Data.Linq.SqlClient.SqlProvider.System.Data.Linq.Provider.IProvider.Execute(Expression query) +500 System.Data.Linq.DataQuery`1.System.Linq.IQueryProvider.Execute(Expression expression) +50 System.Linq.Queryable.FirstOrDefault(IQueryable`1 source) +383 Manager.Controllers.SiteController.Index() in C:\Projects\Manager\Manager\Controllers\SiteController.cs:68 lambda_method(Closure , ControllerBase , Object[] ) +79 System.Web.Mvc.ReflectedActionDescriptor.Execute(ControllerContext controllerContext, IDictionary`2 parameters) +258 System.Web.Mvc.ControllerActionInvoker.InvokeActionMethod(ControllerContext controllerContext, ActionDescriptor actionDescriptor, IDictionary`2 parameters) +39 System.Web.Mvc.&lt;&gt;c__DisplayClassd.&lt;InvokeActionMethodWithFilters&gt;b__a() +125 System.Web.Mvc.ControllerActionInvoker.InvokeActionMethodFilter(IActionFilter filter, ActionExecutingContext preContext, Func`1 continuation) +640 System.Web.Mvc.ControllerActionInvoker.InvokeActionMethodWithFilters(ControllerContext controllerContext, IList`1 filters, ActionDescriptor actionDescriptor, IDictionary`2 parameters) +312 System.Web.Mvc.ControllerActionInvoker.InvokeAction(ControllerContext controllerContext, String actionName) +709 System.Web.Mvc.Controller.ExecuteCore() +162 System.Web.Mvc.&lt;&gt;c__DisplayClass8.&lt;BeginProcessRequest&gt;b__4() +58 System.Web.Mvc.Async.&lt;&gt;c__DisplayClass1.&lt;MakeVoidDelegate&gt;b__0() +20 System.Web.CallHandlerExecutionStep.System.Web.HttpApplication.IExecutionStep.Execute() +453 System.Web.HttpApplication.ExecuteStep(IExecutionStep step, Boolean&amp; completedSynchronously) +371 </code></pre>
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    1. COShow us the code and some stack trace. It might help.
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    2. CO@Steven, updated question with stack trace and code. This specific table and model has not changed for months. It is not isolated to this though - I'm getting this error all over the place. It feels like a data context is being held in memory and after a few seconds a new one is injected, allowing a query to succeed.
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    3. COWhat is happening in the `GetPageCategories` and `GetRevisions` methods. Af far as I know, you can't call native .NET methods when LINQ to SQL has no direct mapping. Did you happen to refactor sub queries of that LINQ query into those methods?
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