public async Task DeleteBeatmapFromCollection(Beatmap beatmap, Collection collection)
{
if (beatmap.IsTemporary)
{
Logger.Warn("需确认加入自定义目录后才可继续");
return;
}
var relation = await Relations
.FirstOrDefaultAsync(k => k.CollectionId == collection.Id && k.BeatmapId == beatmap.Id);
Relations.Remove(relation);
await SaveChangesAsync();
}