Question

How does the implementation of MapRoute connect the {id} in the second parameter to id = in the third?

    routes.MapRoute(
        "Default", // Route name
        "{controller}/{action}/{id}", // URL with parameters
        new { controller = "Home", action = "Index", id = UrlParameter.Optional } // Parameter defaults
    );

Is it as simple as reflecting on the passed in object?

Answer 1

Yes.

It creates a RouteValueDictionary instance from the defaults parameter, which populates itself from the object’s PropertyDescriptors.

You can see this in the source:

if (values != null) { 
    PropertyDescriptorCollection props = TypeDescriptor.GetProperties(values);
    foreach (PropertyDescriptor prop in props) { 
        object val = prop.GetValue(values);
        Add(prop.Name, val);
    }
}