ArcGISRuntimeXamarin.Samples.AuthorEditSaveMap.AuthorEditSaveMap.OnSaveMapClicked C# (CSharp) Method

        private async void OnSaveMapClicked(object sender, EventArgs e)
        {
            try
            {
                // Create a challenge request for portal credentials (OAuth credential request for arcgis.com)
                CredentialRequestInfo challengeRequest = new CredentialRequestInfo();

                // Use the OAuth implicit grant flow
                challengeRequest.GenerateTokenOptions = new GenerateTokenOptions
                {
                    TokenAuthenticationType = TokenAuthenticationType.OAuthImplicit
                };

                // Indicate the url (portal) to authenticate with (ArcGIS Online)
                challengeRequest.ServiceUri = new Uri("http://www.arcgis.com/sharing/rest");

                // Call GetCredentialAsync on the AuthenticationManager to invoke the challenge handler
                await AuthenticationManager.Current.GetCredentialAsync(challengeRequest, false);

                // See if the map has already been saved
                if (!_mapViewModel.MapIsSaved)
                {
                    // Map has not been saved ... save to portal for the first time
                    ShowSaveMapDialog();
                }
                else
                {
                    // Map has previously been saved as a portal item, update it (title and description will remain the same)
                    _mapViewModel.UpdateMapItem();
                    
                    // Report a successful update
                    AlertDialog.Builder dialogBuilder = new AlertDialog.Builder(this);
                    dialogBuilder.SetTitle("Map Updated!");
                    dialogBuilder.SetMessage("Changes to map ('" + _mapViewModel.Map.Item.Title + "' were saved to ArcGIS Online");
                    dialogBuilder.Show();
                }
            }
            catch (System.OperationCanceledException)
            {
                // user canceled the login                
            }
        }