public async Task <IActionResult> OnGetCallback()
{
var result = await HttpContext.AuthenticateAsync(IdentityConstants.ExternalScheme);
if (result?.Succeeded != true)
{
throw new Exception("External authentication error");
}
var(user, provider, providerUserId, claims) = await FindUserFromExternalProviderAsync(result);
var returnUrl = result.Properties.Items["returnUrl"];
if (user == null)
{
var email = result.Principal.Claims.FindEmail();
if (email != null && (user = await _userManager.FindByEmailAsync(email)) == null)
{
// no user found, just add the login to the current user
var currentUser = await _userManager.GetUserAsync(User);
await TryConnectExternalLoginToUser(currentUser, providerUserId, result);
return(ReturnToUrl(returnUrl));
}
}
// either we have:
// * identified a user with the remote login or
// * the remote login has an email that matches a local user record or
// * we have not found any matching user because missing email claim
return(await HandleMerge(user, returnUrl));
}
private async Task <IdentityUser> FindUser(AuthenticateResult result)
{
// For create flow when we have user-id present
if (result.Properties.Items.TryGetValue("userId", out var userId) && userId != null)
{
return(await _userManager.FindByIdAsync(userId));
}
// For login flow when we do not have a user-id
var email = result.Principal.Claims.FindEmail();
if (email != null)
{
return(await _userManager.FindByEmailAsync(email));
}
return(null);
}