asp.net mvc 3 razor view -> strongly typed List of tuple problem

This has been through a few waves of discussion internally now and I'm afraid the final product is that we're not going to be able to fix this for Razor 2.0 (MVC 4). Let me give a little background on the reasoning.

First, it's important to note that the Razor parser intentionally parses the C# as little as possible. The main reason for this is to give you the freedom to the C# you want without us getting in the way. As a result (and you can verify this yourself now by checking out the code!) we do not parse type names in the @inherits and @model directives, we simply run until the end of the line. We are also the parsing engine behind the Razor editor, which means we have to support partially complete statements like @model Foo<Bar which is technically invalid but if you were typing @model Foo<Bar> this would be an expected intermediate step, so we should be able to handle it.

Now, we need to consider what would happen in we decided to change the way we generate code. As the CodeTypeReference documentation states, we would have to use 1[[ ... ]] syntax to define the generic. However, we would still just be inserting whatever the user typed, so if you typed @model Foo<Bar> we'd tell CodeDOM that the base type was something like System.Web.Mvc.WebViewPage`1[[Foo<Bar>]]. As you can see, we still end up with <> in the type name. As a result, we made the decision to use the fact that CodeDOM generally doesn't complain about <> and (Of ...) (in VB) syntax to hack our way around this problem.

Even parsing the whole type name you provided would be difficult given that we'd have to handle incomplete statements like @model Foo<Bar, Baz. In fact, it would also make the editor very brittle, since the editor actually depends on us being able to tell them exactly what range of Razor text maps to what range of C#/VB generated code, and if we introduce additional translation layers (such as the translation CodeDOM will be doing if we use [] or even the other overloads of the CodeTypeReference constructor) we can no longer make those assurances to the editor and you'll see strange behavior

So that leaves us with the workaround, which is to simply avoid using this many generic arguments. There are actually a number of reasons to avoid using Tuple in this way since using a custom model class would allow you to name the properties involved, and would give you greater flexibility when adding properties (with a tuple, you have to update the Controller and View when you want to add a "property" to your tuple). Having said that, we are keeping an eye on this issue and looking at how we can do a better job with this after 4.0. And now that we're open-source, we'd be happy to hear your suggestions and even accept your code!

Please don't hesitate to contact me (email is on my SO profile) or continue discussing this in comments if you have questions. I just wanted to give you the background context you deserve for having put so much excellent work into tracking this down!

-Andrew Nurse (Dev on Razor parser)

I came across this problem today. I was returning some information about user activity, and had attempted to use a model definition of

@model List<Tuple<string,bool,DateTime,DateTime,DateTime>>
@* Name, Online, Created, Login, Active *@

The reason is that I am kind of tired of making single use classes for viewmodels, so that is why I do this for simple use. I received the same error as you. I attempted to bypass the error by using different combinations of tuples in the @model but to no avail.

What did end up working was to simply use the ViewBag. To note, the model is held in the ViewBag anyway so there isn't any issue using it in this capacity.

In my actionresult method, I simply assigned the list of tuples to a viewbag value

ViewBag.listTuple = listOfTuples;

and then in the view I cast i back

@{
    List<Tuple<string,bool,DateTime,DateTime,DateTime>> tuples = ViewBag.listTuple;
}

And that was that. Ran just fine. I am not saying this is the perfect solution but it is a working workaround.

For anyone else who might land here looking for the source of a CS1003 error in a Razor view, the CS1003 error is a general symptom of a failure by MVC to parse the Razor syntax. It could be caused by many things, including the generic tuple problem above.

One thing I've noticed is that this problem will occur if you try to use a C# style single-line comment to annotate the model declaration in a Razor view:

BAD:  @model Int32 // user ID

GOOD: @* user ID *@
      @model Int32

Visual Studio syntax highlighting won't flag it as a problem, but it will fail at runtime.

Just wanted to point out that if you remove the @model directive, you won't have intellisense which actually who cares, but the view works perfectly with any number of tuple arguments.

I ran into this problem because I was using a Tuple of Tuples:

@model Tuple<Tuple<IEnumerable<int>, int, int>, Tuple<float, float, float>>

Needless to say, Razor did not like that. Anyway, I think it's interesting how the parses breaks on the total number of types, rather than the number of types at the top level object.

My workaround

I ended up going with a view model that simple created placeholders for the inside tuples:

public class ViewModel
{
    public Tuple<IEnumerable<int>, int, int> Models { get; set; }
    public Tuple<float, float, float> Selected { get; set; }
}

I'm happy I made the view model. It's more readable and (slightly) easier to manipulate and reason about inside the view.