[HttpGet]
public async Task<IActionResult> ResetPassword(string UserId, string token)
{
...
ApplicationUser user = //get user;
if(!await this._userManager.VerifyUserTokenAsync(user,this._userManager.Options.Tokens.PasswordResetTokenProvider, "ResetPassword", token)){
ViewBag.Message = this._localizer["tokenNotValid"].Value;
}
...
}