Can we skip ResourceManager?

Question

I've working on a project where I'm using ResourceManager extensively and this question just crossed my mind. Can we read from .resx files without using ResourceManager? I mean, is there another way?

Answer 1

ResourceManager is a convenience class, it works very well with the way the build system supports .resx files. No, it is not a strict necessity.

A .NET assembly has the generic capability of embedding arbitrary data into the manifest of the assembly. Just a blob of bytes, it can be anything you want. Directly supported by the build system as well, just add a file to your project and set its Build Action to "Embedded Resource". At runtime, you retrieve the data in that file with Assembly.GetManifestResourceStream().

You can stop right there, but that's just a single file, it doesn't scale very well if you have many small resources you want to embed. Which is where a .resx file starts, it is an XML file that contains resources in a friendly format. One that gives you a fighting chance to recover the source again when the original got lost.

But an XML format is not a very good format for resource data, it is bulky and it is expensive to find data back. So .NET has resgen.exe, a build tool that turns the XML file into a binary file, a .resources file. Compact and easy to find stuff back. And fit to be embedded directly as a single manifest resource.

What you don't want to do is having to read the .resources data yourself. You'll want to use a helper class that can find specific resources back from the blob of bytes. You want use the ResourceReader class, its GetResourceData() lets you specify the resource name and it will spit the resource type and data back out.

You can stop right there, but an app often has a need for different sets of resources. A very common localization need. Which is what satellite assemblies are all about, different assemblies that contain nothing but resources, each for a specific culture. They are separate so you don't pay for the virtual memory that's required to store all the localized resources when you need only one set of them. What's needed here is a helper class that automatically locates and loads the correct satellite assembly and retrieves the resource for you, based on the current culture.

That helper class is ResourceManager.

Answer 2

If you choose to skip the use of the ResourceManager you can let Visual Studio handle code generation for you. Ultimately the generated code uses a ResourceManager, but you're no longer writing that code manually. Additionally, you get compile-time checking since you're referencing a generated static class.

If you add a resource file to your project and double click it from the Solution Explorer, Visual Studio presents you with a dialog where you can enter a name for a resource, and its value. The dialog presents you with options to add resources as strings, images, audio, etc. (look at the dropdowns at the top of the dialog). Next, to get the code generation bit, you need to set the Access Modifier to either "Public" or "Internal". The third option is "No code generation."

For example, add a resource file called "MyResources", then add a string resource with the name Greeting and a value of Hello! With one of the former two options selected for code generation (start off with public to test it, restrict the access as needed), you should now be able to reference the resources from your code via MyResources.Greeting. If you don't see it right away, make sure you've saved the file and try compiling.

string greeting = MyResources.Greeting; // "Hello!"

If you add other resource types (image, audio, etc.) then the return types will differ, of course.

At this point you could inspect the generated .cs file and see that the generated code is using a ResourceManager. The other use for resource files is localization. Let's say you wanted a Spanish version of MyResources. You would add a new file called MyResources.es.resx, where es corresponds to the language code desired (Spanish in this case). Now add the same resource name of Greeting with a Spanish value of Hola!.

If you change the thread culture to Spanish, referencing the resource will now return the Spanish version:

string defaultGreeting = MyResources.Greeting; // "Hello!"
Thread.CurrentThread.CurrentUICulture = CultureInfo.GetCultureInfo("es");
string spanishGreeting = MyResources.Greeting; // "Hola!"

Note that you only really need to set the access modifier to one of the code generation options for your default resource file (i.e., MyResources.resx), not for all the other localized versions you add. There's no harm in doing so, but in my opinion it's cleaner to have the main file generated while the others just have the resource values desired without code generation.

Answer 3

Well, Resources are compiled into the assembly. You could try to read the assembly by reading the bytes (or the IL), and extract the resources from there.

ResourceManager does this all for you, so I could not think of any reason you want to do this... Maybe one, if you don't want to load the assembly in memory, you could do it without ResourceManager.