Specify login_hint using .NET Google.Apis.Oauth2.v2 - google-oauth

Question

Since the Google.Apis.Oauth2.v2 in GoogleWebAuthorizationBroker.AuthorizeAsync() requests a uri to a static json file that contains the links and parameters to Google Oauth2 services, how can I specify the login_hint parameter if I happen to know that information ahead of time?
var credential = await GoogleWebAuthorizationBroker.AuthorizeAsync(
new Uri("ms-appx:///Assets/client_secret.json"),
myScopes,
"user",
CancellationToken.None);
Extract from client_secret.json:
"auth_uri":"https://accounts.google.com/o/oauth2/auth?login_hint=user#domain.com"
How to specify the login_hint parameteron a per user basis?

Answer 1

I ended up subclassing the Google web authorization broker like this:
public class MyOAuth2WebAuthorizationBroker : GoogleWebAuthorizationBroker
{
public static async Task<UserCredential> AuthorizeAsync(ClientSecrets clientSecrets,
IEnumerable<string> scopes, string user, CancellationToken taskCancellationToken)
{
var initializer = new MyOAuth2AuthorizationCodeFlow.Initializer
{
ClientSecrets = clientSecrets,
Scopes = scopes,
DataStore = new StorageDataStore(),
};
var installedApp = new AuthorizationCodeWindowsInstalledApp(new MyOAuth2AuthorizationCodeFlow(initializer, user));
return await installedApp.AuthorizeAsync(user, taskCancellationToken).ConfigureAwait(false);
}
public class MyOAuth2AuthorizationCodeFlow : GoogleAuthorizationCodeFlow
{
private string loginHint { get; set; }
public MyOAuth2AuthorizationCodeFlow(Initializer initializer, string loginHint) : base(initializer)
{
this.loginHint = loginHint;
}
public override AuthorizationCodeRequestUrl CreateAuthorizationCodeRequest(string redirectUri)
{
return new GoogleAuthorizationCodeRequestUrl(new Uri(AuthorizationServerUrl))
{
ClientId = ClientSecrets.ClientId,
Scope = string.Join(" ", Scopes),
RedirectUri = redirectUri,
LoginHint = this.loginHint
};
}
}
}