For Resources access in your C# project, you can open the project properties, select "Resources" on the left.
The first time, the editor will allow to add a resource file by clicking on a link in this editor page (this file will be named "Resources.resx" and will be in the "Properties" subfolder).
Then you will have an editor in which you can add files, strings, images, ...
To access one of those resources in your program, you just have to reference it by something like this :
Image myImageInResource = Properties.Resources.MyImage;
string myStringInResource = Properties.Resources.MyString1;
The full name of a resource in this file will be :
usually, NamespaceOfYourProject is used by default everywhere in your code, and you can ommit it.
After Discussion and your specific problem of using resource with the IrrKlang library
I successfully tried this code:
IrrKlang.ISoundEngine engine = new IrrKlang.ISoundEngine();
IrrKlang.ISoundSource source = engine.AddSoundSourceFromMemory(Properties.Resources.test, "test.mp3");
In this short example, you can see 2 ways to start the sound.
But you must provide a name with its original file extension (in my case ".mp3")
I tried without it, and no sound (nor error) was played.
I think it is a limitation of this IrrKlang library, you might report this as a bug or a possible amelioration to do. I personnaly think it will be nice if the engine report an error when it did not recognise the sound source.
The play2D method always returns an ISound object if playing a sound OR NOT.