Blog.Web.Api.Controllers.AccountController.AddExternalLogin C# (CSharp) Method

        public async Task<IHttpActionResult> AddExternalLogin(AddExternalLoginBindingModel model)
        {
            if (!ModelState.IsValid)
            {
                return BadRequest(ModelState);
            }

            Authentication.SignOut(DefaultAuthenticationTypes.ExternalCookie);

            var ticket = AccessTokenFormat.Unprotect(model.ExternalAccessToken);

            if (ticket == null || ticket.Identity == null || (ticket.Properties != null
                && ticket.Properties.ExpiresUtc.HasValue
                && ticket.Properties.ExpiresUtc.Value < DateTimeOffset.UtcNow))
            {
                return BadRequest("External login failure.");
            }

            var externalData = ExternalLoginData.FromIdentity(ticket.Identity);

            if (externalData == null)
            {
                return BadRequest("The external login is already associated with an account.");
            }

            var result = await UserManager.AddLoginAsync(User.Identity.GetUserId(),
                new UserLoginInfo(externalData.LoginProvider, externalData.ProviderKey));

            return !result.Succeeded ? GetErrorResult(result) : Ok();
        }