Question

I’m testing the ASP.NET MVC 3 OutputCache attribute and the behavior is as follows:

• If you don’t specify a VaryByParam attribute, it will automatically vary by all parameters
• If you specify, it will vary just by those separated by comma like “param1,param2”

But if your Action has a complex parameter, let’s say, a Person, I can’t make it to vary by a property of Person. Let’s say.. Person.Name

I can’t make it to work neighter by saying nothing or explicitly specifying model.Name

Is there a way I can do that?

Answer 1

You can either hack the API a bit by sending Person.Name as an additional parameter (just for the sake of caching), or you can use VaryByCustom attribute option and provide your own resolver. In the second case, you need to edit your Global.asax and override the GetVaryByCustomString method:

public override string GetVaryByCustomString(HttpContext context, string custom)
{
    if(custom == "Person")
    {
        // extract Person.Name here and return it
    }
    return String.Empty;
}

Then add VaryByCustom="Person" to your attribute declaration.