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These constructions are attributes, are not parameters. Part of the syntax is C#. The attribute is just information, called metadata. It alone does nothing. there needs to be a mechanism in the code that reads it and does something.
The ones you are seeing are still personalized. It was ASP.NET MVC that created them, in this case they are called action Filters.
You can create yours as well by following a few rules. Obviously there needs to be a reason to create one and have some mechanism that consumes them.
Ask 3 questions I’m talking about writing these filters: http://answall.com/search?q=user%3A2999+Authorize
– Leonel Sanches da Silva