Александр

LifetimeValidator lifetimeValidator = (DateTime? notBefore, DateTime? expires, SecurityToken securityToken, TokenValidationParameters validationParameters) =>
            {
                if (expires != null && notBefore != null)
                {
                    if (DateTime.UtcNow < expires.Value.ToUniversalTime() & DateTime.UtcNow > notBefore.Value.ToUniversalTime())
                    {
                        return true; // Still valid
                    }
                }
                return false; // Expired
            };

if (_authToken != null & tokenHandler.CanReadToken(_authToken) & _authToken?.Length == 348)
            {
                var jwtSecurityToken = tokenHandler.ReadJwtToken(_authToken);
                SecurityToken validatedToken;
                IPrincipal principal = tokenHandler.ValidateToken(_authToken, GetValidationParameters(), out validatedToken);

                if (lifetimeValidator(validatedToken.ValidFrom, validatedToken.ValidTo, jwtSecurityToken, GetValidationParameters()))
                {
                    if(principal?.Identity?.Name != null)
                    {
                        return true; // Token is valid
                    }
                }
                else
                {
                    return false; // Token is expired
                }
            }
            return false; // Token is damaged
        }