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POAutomapper + EF4 + ASP.NET MVC - getting 'context disposed' error (I know why, but how to fix it?)
 

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  1. POAutomapper + EF4 + ASP.NET MVC - getting 'context disposed' error (I know why, but how to fix it?)
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    <p>I have this really basic code in a MVC controller action. It maps an <code>Operation</code> model class to a very basic <code>OperationVM</code> view-model class . </p> <pre><code>public class OperationVM: Operation { public CategoryVM CategoryVM { get; set; } } </code></pre> <p>I need to load the complete list of categories in order to create a CategoryVM instance.<br> Here's how I (try to) create a <code>List&lt;OperationVM&gt;</code> to show in the view. </p> <pre><code>public class OperationsController : Controller { private SomeContext context = new SomeContext (); public ViewResult Index() { var ops = context.Operations.Include("blah...").ToList(); Mapper.CreateMap&lt;Operation, OperationVM&gt;() .ForMember( dest =&gt; dest.CategoryVM, opt =&gt; opt.MapFrom( src =&gt; CreateCatVM(src.Category, context.Categories) // trouble here ----------------^^^^^^^ ) ); var opVMs = ops.Select(op =&gt; Mapper.Map&lt;Operation, OperationVM&gt;(op)) .ToList(); return View(opVMs); } } </code></pre> <p>All works great first time I hit the page. The problem is, the mapper object is static. So when calling <code>Mapper.CreateMap()</code>, the instance of the current <code>DbContext</code> is saved in the closure given to CreateMap().</p> <p>The 2nd time I hit the page, the static map is already in place, still using the reference to the initial, now disposed, <code>DbContext</code>.</p> <p>The exact error is:</p> <pre><code>The operation cannot be completed because the DbContext has been disposed. </code></pre> <p>The question is: How can I make AutoMapper always use the <em>current</em> context instead of the initial one?</p> <p>Is there a way to use an "instance" of automapper instead of the static <code>Mapper</code> class? If this is possible, is it recommended to re-create the mapping every time? I'm worried about reflection slow-downs.</p> <p>I read a bit about custom resolvers, but I get a similar problem - How do I get the custom resolver to use the current context?</p>
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    1. USCristi Diaconescu
    1. USCristi Diaconescu
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    1. COYeah, this seems to be a weakness with using EF with AutoMapper. I've run into the same problem when trying to map a DTO back to an entity. Hopefully you'll find the secret. I was forced to make my own cludgy static method, and would love to be able to ditch it for a real solution.
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    2. COWhy you pass context.Categories. Try to iterate before pass it to automapper. use var categories = context.Categories.ToArray() and pass categories to CreateCatVM method.
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      1. USKirill Bestemyanov
    3. CO@KirillBestemyanov The call to `Mapper.CreateMap(...)` should really only be called once, e.g. from a static ctor, not each time I need to map objects. And the list of categories may well change in between.
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      1. USCristi Diaconescu
 

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