SPOILER

1. Reading and writing beatmaps and storyboards
2. Retrieving data from the API
3. Reading replay data

1. Read and write beatmaps (.osu), includes loading everything into objects (such as timingpoints, hitobjects, spritevents...)
2. Read and write storyboards (.osb)
3. Read and write skins (skin.ini)
4. Read replays (.osr)
5. Read and write collections (collection.db)
6. Read scores (scores.db)
7. Read the beatmap database (osu!.db)

1. Open an existing storyboard/ beatmap or make a new Stoyboard() object
2. Add Sprites/Animations, Add transformations to those, and even add Samples
3. optional: use the Variables functionality by adding keys and values to the VariablesDictionary
4. Save to a new or existing storyboard/beatmap

Anything else
Make a custom replay viewer, or even a complete clone of osu, if you want that.
Make a collections editor, using beatmap search functionality (with osu.db) or by score achieved (scores.db) --might do this myself though :p
... use your imagination!

using osuElements;
using osuElements.Beatmaps;

var beatmap = new Beatmap(@"1 Kenji Ninuma - DISCO PRINCE\Kenji Ninuma - DISCOüÜPRINCE (peppy) [Normal].osu");
beatmap.Version = "THIS MAP IS GREAT";
beatmap.Diff_Approach = 9.5f;
var hitcircle = new HitCircle(new Position(10, 20), 200); 
beatmap.HitObjects.Add(hitcircle);
beatmap.FileName = "Kenji Ninuma - DISCOüÜPRINCE (peppy) [Improved version].osu";
beatmap.WriteFile(); 

using osuElements.Api.Repositories;

var bRep = new ApiBeatmapRepository();
var firstMap = await bRep.Get(1);
var someManiaMap = await bRep.Get("ds12dza68123sdq564", GameMode.Mania);
var mapsByMe = await bRep.GetCreator("ExCellRaD", limit: 5);
var scoresOnMap = bRep.GetScores(firstMap.Beatmap_Id);
var maps2016 = bRep.GetSince(new DateTime(2016, 1, 1));

var uRep = new ApiUserRepository();
var peppy = await uRep.Get("peppy");
var peppyscores = await uRep.GetBest(peppy.User_Id, GameMode.CatchTheBeat);
var recentscores = await uRep.GetRecent("Rafis");

var mRep = new ApiMultiplayerRepository();
var match = await mRep.Get(123456);
var games = match.Games;

Sh0keR wrote:

By reading beapmaps do you mean i can get the full information of a beatmap. Including title creator hit circles etc.
Edit
I meant do i need an api key or i can directly read and write beatmaps

Sh0keR wrote:

After messing with it for a few hours, it's pretty cool and work well!
I have an issue though with retrieving some of the information from a beatmap, but I think it's because I need an API key, is that true?

the properties I am having issues with (they are always the same or empty)

Approved, Total_Length, Hit_Length, File_MD5(empty), Approved Date, Last Update, BPM, Source, GeneralID, Language_ID, Favorutie_Count, PlayCount,
PassCount, Max_Combo (Empty), DifficultyRating, BeatmapDifficulty (Always easy)

ExCellRaD wrote:

Sh0keR wrote:

After messing with it for a few hours, it's pretty cool and work well!
I have an issue though with retrieving some of the information from a beatmap, but I think it's because I need an API key, is that true?

the properties I am having issues with (they are always the same or empty)

Approved, Total_Length, Hit_Length, File_MD5(empty), Approved Date, Last Update, BPM, Source, GeneralID, Language_ID, Favorutie_Count, PlayCount,
PassCount, Max_Combo (Empty), DifficultyRating, BeatmapDifficulty (Always easy)

Yeah those do come from the API, and the reason why they're there are because Beatmap inherits from ApiBeatmap. You can get the File_MD5 from using the GetHash() method and calculate max_como, hit_length and total_length with HitObjects.
Would it be less confusing if Beatmap didn't inherit from ApiBeatmap? Be sure to tell me if this seems wrong to you, I can always find a better solution.

Sh0keR wrote:

"Title" also inherits from ApiBeatmaps but it works just fine?
I have a feeling I am just confused about some stuff.