{id:int?} should act as optional

[yishaigalatzer]

No description provided.

[rynowak]

What's the behavior in MVC5? I don't think any of our constraints know about optionality.

[yishaigalatzer]

Interesting. I was thinking optionallity could trump constraint for the same key.

[kichalla]

In MVC5 (MVC and Web API attribute routing) the integer constraint only gets evaluated when there is a value in this case, so I think this is a bug...

[rynowak]

In MVC5 (MVC and Web API attribute routing) the integer constraint only gets evaluated when there is a value in this case, so I think this is a bug...

If this were true, then global constraints via attribute routing wouldn't work at all. (there are constraints for which there is never a route value).

If I try the following definition in MVC, I can get to my action with /Home/Index/5, but not /Home/Index:

            routes.MapRoute(
                "default",
                "{controller}/{action}/{id}",
                new { id = UrlParameter.Optional, },
                new { id = new IntRouteConstraint(), });

[kichalla]

Good point!, Ryan...will investigate to see why it works in case of attribute routing...

[kichalla]

So it seems like in case of attribute routing in MVC5, for the above scenario, the inline route template parser wraps the IntRouteConstraint inside an OptionalRouteConstraint...

InlineRouteRemplateParser
http://aspnetwebstack.codeplex.com/SourceControl/latest#src/Common/Routing/InlineRouteTemplateParser.cs
Code of interest

if (parameterConstraints.Count > 0)
{
    var constraint = parameterConstraints.Count == 1 ?
        parameterConstraints[0] :
        new CompoundRouteConstraint(parameterConstraints);

    if (isOptional)
    {
        // Constraints should match RouteParameter.Optional if the parameter is optional
        // This prevents contraining when there's no value specified
        constraint = new OptionalRouteConstraint(constraint);
    }

    return constraint;
}

OptionalRouteConstraint
http://aspnetwebstack.codeplex.com/SourceControl/latest#src/Common/Routing/Constraints/OptionalRouteConstraint.cs

[rynowak]

That's pretty cool, I didn't know we dealt with that. If we want to fix this we should do it for conventional and attribute routes.

[yishaigalatzer]

@rynowak you are on it, or pick a victim.

There is one wierdness around the Required constraint. But you got yourself in it if you wrote it, and it's not that interesting anyways.

[kulmugdha]

f549a55 -- this fixes the routing part.
ba8cf3ca4617ee4b5a15ac45a88c2bb36418b3e1 -- this fixes the MVC part