Strange behaviour with StructureMap / ASP.MVC / Visual Studio / LinqToSql

Question

I have been using the new MVC framework with StructureMap recently and have had good results overall, however, I keep running into a very strange error that I cannot underst

Answer 1

One common mistake when using DI containers with ASP.NET MVC is that many DI containers default to a Singleton pattern. I don't know if that's the case here, but you should double check. ASP.NET MVC requires that the controller is created on every request because it has per-request state and context.

Answer 2

I was talking to Jeremy Miller about this and you don't want to manage the lifetime of the db context with SM - let the repo instantiate as needed. This presents problems with how you will do object updating/persistence (if you're relying on a context staying alive for more than one request) but it's worth it to not rely on this for a web app.

I had to remove the db context management stuff from the storefront for a reason like this - I was getting memory leaks. I won't say it's SM's fault - but overall just let the repo open a new context.

Answer 3

Add:

MultipleActiveResultSets=True

To the end of your connection string (assuming MSSQL 2005+)

To do this for your linq context: Open the properties tab -> Expand Connection -> Click the "..." on 'Connection String' -> 'Advanced' -> 'MultipleActiveResultSets' -> true.

I solved this one myself today and my architecture is almost identical (save for unity instead of structure map). Including the two controllers being loaded via JS!

Answer 4

Are you completely sure nothing along in the object hierarchy is being Cached / or has a lifetime config? I have a prod app with a config just like this:

    ForRequestedType<SomeDataContext>().TheDefault.Is.ConstructedBy(
        () => new SomeDataContext(someConnString);

It isn't using asp.net MVC. Regarding the scoping issue, if you haven't set up anything, structure map will default to PerRequest (not asp.net request but structure map request, like each .GetInstance call) - http://structuremap.sourceforge.net/Scoping.htm. If you are positive on no configuration to affect it, then look at whether the mvc contrib or something else might be reusing instances.

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Regarding the exception info posted. The error involves a combination of action results, action result filters, json serialization, custom methods, and also one linq2sql call failing because of an unexpected null. That's a combination of many different pieces, some of which I don't know. I would play safer and move the calculate stuff (that calls into linq2sql) being called when doing serialization to somewhere else where the json serialization/action results pieces aren't involved. This is just a wild guess, as I don't know how/when those pieces are called and what type of actions they have internally.