/// <summary>
        /// Sends an e-mail with instructions on resetting the user password.
        /// </summary>
        /// <param name="viewModel">Represents the view model of the e-mail.</param>
        public async Task SendPasswordResetEmailAsync(EmailPasswordResetViewModel viewModel)
        {
            // Define the variables for the e-mail.
            var apiKey      = _configuration.GetSection("Authentication:SendGrid:AppKey").Value;
            var client      = new SendGridClient(apiKey);
            var from        = new EmailAddress(_configuration.GetSection("EmailSender:Email").Value, _configuration.GetSection("EmailSender:Name").Value);
            var to          = new EmailAddress(viewModel.Email, viewModel.Email);
            var subject     = "NetControl4BioMed - Reset your password";
            var htmlContent = await _renderer.RenderPartialToStringAsync("_EmailPasswordResetPartial", viewModel);

            var msg = MailHelper.CreateSingleEmail(from, to, subject, string.Empty, htmlContent);
            // Send the e-mail containing the URL.
            await client.SendEmailAsync(msg);
        }
        public async Task <IActionResult> OnPostAsync()
        {
            // Check if the reCaptcha is valid.
            if (!await _reCaptchaChecker.IsValid(Input.ReCaptchaToken))
            {
                // Add an error to the model.
                ModelState.AddModelError(string.Empty, "The reCaptcha verification failed.");
                // Return the page.
                return(Page());
            }
            // Check if the provided model is not valid.
            if (!ModelState.IsValid)
            {
                // Add an error to the model.
                ModelState.AddModelError(string.Empty, "An error was encountered. Please check again the input fields.");
                // Return the page.
                return(Page());
            }
            // Get the user with the provided e-mail.
            var user = await _userManager.FindByEmailAsync(Input.Email);

            // Check if there wasn't any user found.
            if (user == null)
            {
                // Display a message.
                TempData["StatusMessage"] = "Error: The provided e-mail address is not associated with any user.";
                // Redirect to the page.
                return(RedirectToPage("/Account/Index"));
            }
            // Generate the password reset code for the user.
            var code = await _userManager.GeneratePasswordResetTokenAsync(user);

            // Get the callback URL to be encoded in the e-mail.
            var callbackUrl = _linkGenerator.GetUriByPage(HttpContext, "/Identity/ResetPassword", handler: null, values: new { code = code });
            var encodedUrl  = HtmlEncoder.Default.Encode(callbackUrl);
            // Define a new view model for the e-mail.
            var emailViewModel = new EmailPasswordResetViewModel
            {
                Email          = user.Email,
                Url            = encodedUrl,
                ApplicationUrl = _linkGenerator.GetUriByPage(HttpContext, "/Index", handler: null, values: null)
            };
            // Send the password reset e-mail for the user.
            await _emailSender.SendPasswordResetEmailAsync(emailViewModel);

            // Display a message.
            TempData["StatusMessage"] = "Success: Please check your e-mail. A message containing instructions for resetting your password has been sent.";
            // Redirect to the home page.
            return(RedirectToPage("/Index"));
        }