public async Task RemoveClaims(string userId, string[] claimTypes)
{
long u = long.Parse(userId);
var query = from claim in _db.Set <Claim>()
where claim.UserId == u
where claimTypes.Contains(claim.Type)
select claim;
var claims = await query.ToListAsync();
_db.RemoveRange(claims);
await _db.SaveChangesAsync();
}