Unsurprisingly, Microsoft do have a how-to for developing licensed components. There's also a nice diagram here. Some of the information presented in these tutorials is a little misleading, so I figured I'd get back to trying on my hats.
Hat 1I've developed the one component that could change the world. That's a little c, not big C for component. There's no requirement for my class to fit into Microsoft's ComponentModel namespace (which is, incidentally, where all the bog standard licensing classes reside). So, I apply the [LicenseProvider(typeof(LicFileLicenseProvider))] to my fantastic class, and somewhere in the class I make a call to the static method LicenseManager.Validate(passing in the type of my class, as this is how the manager figures out that I wanted it to use the LicFileLicenseProvider). There are two overloads for Validate:
a) public static License Validate(Type type, object instance)
b) public static void Validate(Type type)
Option #1 offers the fullest functionality and it makes sense to make the call in my class's constructor - after all, the error message (of the LicenseException that's thrown if the call to Validate fails for some reason) WANTS me to do this: "An instance of type 'Elsie.Proprietary.Fantastic' was being created, and a valid license could not be granted for the type 'Elsie.Proprietary.Fantastic'. Please, contact the manufacturer of the component for more information." Because the call to Validate returns a new disposable License object, I'm responsible at least for ensuring it gets cleaned up properly. I'll assign it to an instance field, and make my class implement IDisposable.
Option #2 is a little less messy - I don't have to pass in an instance of my class, I don't have to worry about managing a Licence object's lifetime. "A valid license cannot be granted for the type Elsie.Proprietary.Fantastic. Contact the manufacturer of the component for more information."
That's it. I don't even have to create a license file.
Hat 2I'm going to use the Fantastic class, so I mock up a new project of my own (which I call Elsie.Target.exe) and I add an assembly reference to it. Then I create (probably in notepad2.exe) a one line txt file: inside it I type "Elsie.Propietary.Fantastic is a licensed component". I make sure the file is called "Elsie.Propietary.Fantastic.lic" and I make sure it's copied to my working directory (probably by setting BuildAction:Content, and CopyToOutput:CopyAlways). Inside my application, I call the Fantastic constructor (within a using statement, because the class implements IDisposable, because the component deveoper was a responsible guy after all). Hidden inside the constructor, Fantastic checks if I'm allowed to use it by loading the .lic file. If the checks are successful, I go on my way to being a superstar developer. Otherwise, an exception will be thrown and it's back to the streets for me!
Hat 3I'm in the London office at 7am. I deployed Elsie.Target.exe, along with Elsie.Propietary.dll and Elsie.Propietary.Fantastic.lic last night. While I've been sleeping, everyone in APAC has been delighted with just how fantastic the application is. In my excitement, I forget about being a cheeky monkey and changing the .lic file contents to read "... is *not* a licensed component". This is lucky for me, because it would BREAK the application!
Good: "Elsie.Proprietary.Fantastic is a licensed component."
Good: "Elsie.Proprietary.Fantastic is a licensed component. Yes it is!"
Good: "Elsie.Proprietary.Fantastic is a licensed component. NOT!"
Bad: "Elsie.Proprietary.Fantastic is a licensed component"
Bad: "Elsie.Proprietary.Fantastic is not a licensed component"
It turns out that the Key is valid if the text in the file starts with the fully qualified type name followed by " is a licensed component."
This is crazy! So crazy, in fact, that it might just work...