C# Named parameters to a string that replace to the parameter values

I want in a good performance way (I hope) replace a named parameter in my string to a named parameter from code, example, my string:

"Hi {name}, do you like milk?"

How could I replace the {name} by code, Regular expressions? To expensive? Which way do you recommend?

How do they in example NHibernates HQL to replace :my_param to the user defined value? Or in ASP.NET (MVC) Routing that I like better, "{controller}/{action}", new { controller = "Hello", ... }?