public async Task <Exercise> Add(string name, string description) { if (string.IsNullOrWhiteSpace(name)) { throw new ArgumentNullException(name); } if (string.IsNullOrWhiteSpace(description)) { throw new ArgumentNullException(description); } var exercise = await Get(name); if (exercise != null) { throw new EntityExistsException($"Exercise with name {name} already exists."); } exercise = new Exercise { Name = name, Description = description }; _context.Exercises.Add(exercise); await _context.SaveChangesAsync(); return(exercise); }