MVC :: Chart Controls Returned As FileResult?

I wanted to use the ASP.NET Chart Controls, but since all of the available examples used a code-behind page reminiscent of Web Forms, I shied away from this. Then I found an example returning the Chart Control as a FileResult, and tried it out. It worked, I was happy and all was good in the world. Except that occasionally I'll get a broken link showing instead of the image it should resolve to.

Here's how I have it set up:

In the View, the code is very simple. It's just an image tag that has its src attribute set to the Controller method. I didn't realize this was possible, and thought it pretty cool:

[Code]....

In the Controller, I instantiate and build the Chart Control in its entirety, and then output it as a FileResult:

[Code]....

Yes, it's a bit long and involves, but that's what you get when programmatically building something inititally set up to be a server control. All of this works, and even when I get the output that shows a broken link, if I refresh the page, it generally fixes itself. Here's the code from the FileResult created for this purpose - it's not a Controller, but I placed it in with the Controllers just while testing:

[Code]....

I'm thinking that the reason behind the occasional broken link is related to the DataContext object, not any of the above code. It seems reasonable that if the DataContext doesn't build and return a FileResult quickly enough, perhaps because it's doing too many other things, the broken link would show because no file had been built where it was expected. I've included the code anyway, in case someone can find an issue that would cause the problems I've been encountering. Any advice would be greatly appreciated. I had this working with Flex chart components that I genericized so that they worked with MVC methods, but they were way too slow to complete rendering. It often took 3-7 seconds, which was just too long for a user to wait for their page to load. These Chart Controls are really fast and are a perfect solution - if I can get them to render consistently.