public async Task <ActionResult> OnPostRegister(int?id, [FromServices] UserManager <User> userManager)
{
User = await userManager.GetUserAsync(HttpContext.User);
CompetitionDto = _competitionService.GetCompetitions().Single(c => c.Id == id);
Participation par = new Participation()
{
CompetitionId = CompetitionDto.Id,
UserId = User.Id
};
_participationService.addParticipation(par);
return(Redirect($"./Details?id=" + id));
}