IdentityServer4 External Authentication (Azure Active Directory) fails - identityserver4

Question

I created project from template: "is4aspid" and added Azure Active Directory authentication.
In Startup.cs added this code:
// preserve OIDC state in cache (solves problems with AAD and URL lenghts)
services.AddOidcStateDataFormatterCache();
// cookie policy to deal with temporary browser incompatibilities
services.AddSameSiteCookiePolicy();
services.AddAuthentication()
.AddOpenIdConnect("aad", "Sign-in with Azure AD", options =>
{
options.Authority = "https://login.microsoftonline.com/common";
options.ClientId = "myClientId";
options.ClientSecret = "myClientSecret";
options.SignInScheme = IdentityServerConstants.ExternalCookieAuthenticationScheme;
options.SignOutScheme = IdentityServerConstants.SignoutScheme;
options.ResponseType = "id_token";
options.CallbackPath = "/signin-aad";
options.SignedOutCallbackPath = "/signout-callback-aad";
options.RemoteSignOutPath = "/signout-aad";
options.TokenValidationParameters = new TokenValidationParameters
{
ValidateIssuer = false,
ValidateAudience = false,
NameClaimType = "name",
RoleClaimType = "role"
};
});
I added redirect uri on Azure: http://localhost:5000/signin-aad
Error occure where Callback method is called.
HttpContext.AuthenticateAsync(IdentityConstants.ExternalScheme) Success is always false
[HttpGet]
public async Task<IActionResult> Callback()
{
var result = await HttpContext.AuthenticateAsync(IdentityConstants.ExternalScheme);
if (result?.Succeeded != true)
{
throw new Exception("External authentication error");
}
// some code
}
Where is my error?

Answer 1

Solution
Must define IdentityConstants.ExternalScheme in startup and callback