NavigationStack has a problem with ScanPage












0














I have a problem with the scan in a Xamarin app. It's just difficult to explain. I have 4 pages in my app. My Scan is open with a button in the 4th page. When i used the scan the first time i have no problem. As Long as stay on the 4th page i have no problem i can do a lot of scan with no error. But when i use the button Go Back in my app and i go on the 3th page and after i return to the 4th page and i used the scan i have an error.



System.ArgumentOutOfRangeException: Index was out of range. Must be non-negative and less than the size of the collection.

Parameter name: index


At this moment my navigationStack is equal to 0.



My method GoBack just do:




Navigation.PopAsync();




And the scanner bug when i scan my QRCode and i call SendPresenceAck()



private async Task SendPresenceAck(string paramA09) //, int? idPrestation)

    {



        int idParticipant;

        if (!int.TryParse(paramA09, out idParticipant))

        {

            //await this.ShowAlert("Attention", "Problème de lecture du QR Code.");

            await this.DisplayAlert("Attention", "Problème de lecture du QR Code.", "Cancel");



            return;

        }



        // On appelle le WS pour signifier la présence

        // On passe par validateService

        // On prépare la validation de la présence

        var validateService = new ValidatePresenceService(this.Token);



        // On ajoute la ligne à valider

        var validate = validateService.AddNewPresence(idParticipant, this.idPrestation, true);



        // On déclenche l'envoi au WS (si besoin)

        if (validate != null)

        {

            // On envoie uniquement en cas de connexion

            if (!Global.GetSettingsBool(TypeSettings.IsHorsConnexion))

            {

                //await validateService.SendAll();

                // Attention : si participant déjà enregistré : erreur 403

                try

                {

                    await validateService.Send(validate);

                    // await this.DisplayAlert("OK", "Le billet est validé.", "OK");

                    popupLoginView.IsVisible = true;

                    //Gestion du premier stack et du bouton

                    StckSLayout.BackgroundColor = Color.FromHex("#DD5500");

                    ImageBack.BackgroundColor = Color.White;

                    //BoxSEmpty.BackgroundColor= Color.FromHex("#DD5500");

                    button.BackgroundColor = Color.FromHex("#DD5500");

                    button.Text = "Blabla";

                    //BoxSEmpty.Clicked += boutonSortir;

                    button.Clicked += async (sender, e) =>

                    {

                        // Ouverture du scan

                        await BtnScanClicked(sender, e);







                    };

                    //Gestion à partir du deuxième stack

                    StckSLayoutMiddle.BackgroundColor = Color.FromHex("#DD7700");

                    LbldAlert.BackgroundColor = Color.FromHex("#641914");

                    LbldAlert.Text = "ALERTE";

                    LblSEnd.BackgroundColor = Color.FromHex("#641914");

                    LblSEnd.Text = "Blabla";

                    // 401 : impossible d'identifier le numéro du billet

                    //  await this.DisplayAlert("Attention", "Impossible d'identifier le numéro du billet, veuillez vérifier les informations de celui ci.", "Cancel");

                    //   return;







                }

                catch (WebException ex)

                {

                    HttpWebResponse objresponse = ex.Response as HttpWebResponse;

                    if (objresponse.StatusCode == HttpStatusCode.Forbidden)

                    {

                        popupLoginView.IsVisible = true;

                        //Gestion du premier stack et du bouton

                        StckSLayout.BackgroundColor = Color.FromHex("#DD5500");

                        ImageBack.BackgroundColor = Color.White;

                        //BoxSEmpty.BackgroundColor= Color.FromHex("#DD5500");

                        button.BackgroundColor = Color.FromHex("#DD5500");

                        button.Text = "Blabla";

                        //BoxSEmpty.Clicked += boutonSortir;

                        button.Clicked += async (sender, e) =>

                        {

                            // Ouverture du scan

                            await BtnScanClicked(sender, e);







                        };

                        //Gestion à partir du deuxième stack

                        StckSLayoutMiddle.BackgroundColor = Color.FromHex("#DD7700");

                        LbldAlert.BackgroundColor = Color.FromHex("#641914");

                        LbldAlert.Text = "ALERTE";

                        LblSEnd.BackgroundColor = Color.FromHex("#641914");

                        LblSEnd.Text = "Blabla";

                        // 403 : le participant a déjà été enregistré aujourd'hui

                        // Message d'erreur

                        // await this.DisplayAlert("Attention", "Le billet a déjà été enregistré, le numéro du billet a déjà été scanné auparavant.", "OK");

                        // return;



                    }

                    else if (objresponse.StatusCode == HttpStatusCode.NotFound)

                    {

                        popupLoginView.IsVisible = true;

                        //Gestion du premier stack et du bouton

                        StckSLayout.BackgroundColor = Color.FromHex("#DD5500");

                        ImageBack.BackgroundColor = Color.White;

                        //BoxSEmpty.BackgroundColor= Color.FromHex("#DD5500");

                        button.BackgroundColor = Color.FromHex("#DD5500");

                        button.Text = "Blabla";

                        //BoxSEmpty.Clicked += boutonSortir;

                        button.Clicked += async (sender, e) =>

                        {





                            // Ouverture du scan

                            await BtnScanClicked(sender, e);







                        };

                        //Gestion à partir du deuxième stack

                        StckSLayoutMiddle.BackgroundColor = Color.FromHex("#DD7700");

                        LbldAlert.BackgroundColor = Color.FromHex("#641914");

                        LbldAlert.Text = "ALERTE";

                        LblSEnd.BackgroundColor = Color.FromHex("#641914");

                        LblSEnd.Text = "Blabla";

                        // 404 : billet non valide



                        // await this.DisplayAlert("Attention", "Le billet n'est pas valide.", "Cancel");



                        //return;

                    }

                    else if (objresponse.StatusCode == HttpStatusCode.Unauthorized)

                    {

                        popupLoginView.IsVisible = true;

                        //Gestion du premier stack et du bouton

                        StckSLayout.BackgroundColor = Color.FromHex("#DD5500");

                        ImageBack.BackgroundColor = Color.White;

                        //BoxSEmpty.BackgroundColor= Color.FromHex("#DD5500");

                        button.BackgroundColor = Color.FromHex("#DD5500");

                        button.Text = "Blabla";

                        //BoxSEmpty.Clicked += boutonSortir;

                        button.Clicked += async (sender, e) =>

                        {

                            // Ouverture du scan

                            await BtnScanClicked(sender, e);







                        };

                        //Gestion à partir du deuxième stack

                        StckSLayoutMiddle.BackgroundColor = Color.FromHex("#DD7700");

                        LbldAlert.BackgroundColor = Color.FromHex("#641914");

                        LbldAlert.Text = "ALERTE";

                        LblSEnd.BackgroundColor = Color.FromHex("#641914");

                        LblSEnd.Text = "Blabla";

                        // 401 : impossible d'identifier le numéro du billet

                        //  await this.DisplayAlert("Attention", "Impossible d'identifier le numéro du billet, veuillez vérifier les informations de celui ci.", "Cancel");

                        //   return;



                    }

                }

                catch (Exception e)

                {

                    // Erreur

                    await this.DisplayAlert("Attention", e.Message, "Cancel");

                    return;

                }

            }

            else

            {

                // Hors connexion : on vérifie juste si l'utilisateur n'est pas déjà présent dans la table SQL



                // Attention : si pas de prestation : on a le droit d'enregistrer plusieurs fois la présence

                // Si il y a une prestation, en revanche, on doit vérifier qu'il n'est pas déjà inscrit



                if (validate.IdPrestation.HasValue &&

                    validateService.IsInscriptionAlreadyRecorded(validate))

                {

                    popupLoginView.IsVisible = true;



                    //Gestion du premier stack et du bouton

                    StckSLayout.BackgroundColor = Color.FromHex("#DD5500");

                    ImageBack.BackgroundColor = Color.White;

                    //BoxSEmpty.BackgroundColor= Color.FromHex("#DD5500");

                    button.BackgroundColor = Color.FromHex("#DD5500");

                    button.Text = "Blabla";

                    //BoxSEmpty.Clicked += boutonSortir;

                    button.Clicked += async (sender, e) =>

                    {





                        // Ouverture du scan

                        await BtnScanClicked(sender, e);







                    };

                    //Gestion à partir du deuxième stack

                    StckSLayoutMiddle.BackgroundColor = Color.FromHex("#DD7700");

                    LbldAlert.BackgroundColor = Color.FromHex("#641914");

                    LbldAlert.Text = "ALERTE";

                    LblSEnd.BackgroundColor = Color.FromHex("#641914");

                    LblSEnd.Text = "Blabla";



                    // Déjà trouvé : message d'erreur

                    // await this.DisplayAlert("Attention", "Le participant a déjà été enregistré.", "OK");

                    //

                    // return;





                }



            }

        }

        else

        {

            // Pb à l'insertion des données ??



        }





        return;





    }


The exception is on the line: 



popupLoginView.IsVisible = true;


Sorry it's very hard to explain and i'm not english so i hope somebody understand and help me.
Thanks.






c# xamarin stack qr-code







share|improve this question
























  • On which line does the Exception get thrown?
    – MindSwipe
    Nov 12 '18 at 14:50










  • Seems you were trying to index an object with a value that was not valid. Check your code about list in your project when you scan.
    – Jack Hua - MSFT
    Nov 15 '18 at 8:11










  • The only list i have is my NavigationStack whose become empty just during the scan.
    – Kanok
    Nov 22 '18 at 10:06
















0














I have a problem with the scan in a Xamarin app. It's just difficult to explain. I have 4 pages in my app. My Scan is open with a button in the 4th page. When i used the scan the first time i have no problem. As Long as stay on the 4th page i have no problem i can do a lot of scan with no error. But when i use the button Go Back in my app and i go on the 3th page and after i return to the 4th page and i used the scan i have an error.



System.ArgumentOutOfRangeException: Index was out of range. Must be non-negative and less than the size of the collection.

Parameter name: index


At this moment my navigationStack is equal to 0.



My method GoBack just do:




Navigation.PopAsync();




And the scanner bug when i scan my QRCode and i call SendPresenceAck()



private async Task SendPresenceAck(string paramA09) //, int? idPrestation)

    {



        int idParticipant;

        if (!int.TryParse(paramA09, out idParticipant))

        {

            //await this.ShowAlert("Attention", "Problème de lecture du QR Code.");

            await this.DisplayAlert("Attention", "Problème de lecture du QR Code.", "Cancel");



            return;

        }



        // On appelle le WS pour signifier la présence

        // On passe par validateService

        // On prépare la validation de la présence

        var validateService = new ValidatePresenceService(this.Token);



        // On ajoute la ligne à valider

        var validate = validateService.AddNewPresence(idParticipant, this.idPrestation, true);



        // On déclenche l'envoi au WS (si besoin)

        if (validate != null)

        {

            // On envoie uniquement en cas de connexion

            if (!Global.GetSettingsBool(TypeSettings.IsHorsConnexion))

            {

                //await validateService.SendAll();

                // Attention : si participant déjà enregistré : erreur 403

                try

                {

                    await validateService.Send(validate);

                    // await this.DisplayAlert("OK", "Le billet est validé.", "OK");

                    popupLoginView.IsVisible = true;

                    //Gestion du premier stack et du bouton

                    StckSLayout.BackgroundColor = Color.FromHex("#DD5500");

                    ImageBack.BackgroundColor = Color.White;

                    //BoxSEmpty.BackgroundColor= Color.FromHex("#DD5500");

                    button.BackgroundColor = Color.FromHex("#DD5500");

                    button.Text = "Blabla";

                    //BoxSEmpty.Clicked += boutonSortir;

                    button.Clicked += async (sender, e) =>

                    {

                        // Ouverture du scan

                        await BtnScanClicked(sender, e);







                    };

                    //Gestion à partir du deuxième stack

                    StckSLayoutMiddle.BackgroundColor = Color.FromHex("#DD7700");

                    LbldAlert.BackgroundColor = Color.FromHex("#641914");

                    LbldAlert.Text = "ALERTE";

                    LblSEnd.BackgroundColor = Color.FromHex("#641914");

                    LblSEnd.Text = "Blabla";

                    // 401 : impossible d'identifier le numéro du billet

                    //  await this.DisplayAlert("Attention", "Impossible d'identifier le numéro du billet, veuillez vérifier les informations de celui ci.", "Cancel");

                    //   return;







                }

                catch (WebException ex)

                {

                    HttpWebResponse objresponse = ex.Response as HttpWebResponse;

                    if (objresponse.StatusCode == HttpStatusCode.Forbidden)

                    {

                        popupLoginView.IsVisible = true;

                        //Gestion du premier stack et du bouton

                        StckSLayout.BackgroundColor = Color.FromHex("#DD5500");

                        ImageBack.BackgroundColor = Color.White;

                        //BoxSEmpty.BackgroundColor= Color.FromHex("#DD5500");

                        button.BackgroundColor = Color.FromHex("#DD5500");

                        button.Text = "Blabla";

                        //BoxSEmpty.Clicked += boutonSortir;

                        button.Clicked += async (sender, e) =>

                        {

                            // Ouverture du scan

                            await BtnScanClicked(sender, e);







                        };

                        //Gestion à partir du deuxième stack

                        StckSLayoutMiddle.BackgroundColor = Color.FromHex("#DD7700");

                        LbldAlert.BackgroundColor = Color.FromHex("#641914");

                        LbldAlert.Text = "ALERTE";

                        LblSEnd.BackgroundColor = Color.FromHex("#641914");

                        LblSEnd.Text = "Blabla";

                        // 403 : le participant a déjà été enregistré aujourd'hui

                        // Message d'erreur

                        // await this.DisplayAlert("Attention", "Le billet a déjà été enregistré, le numéro du billet a déjà été scanné auparavant.", "OK");

                        // return;



                    }

                    else if (objresponse.StatusCode == HttpStatusCode.NotFound)

                    {

                        popupLoginView.IsVisible = true;

                        //Gestion du premier stack et du bouton

                        StckSLayout.BackgroundColor = Color.FromHex("#DD5500");

                        ImageBack.BackgroundColor = Color.White;

                        //BoxSEmpty.BackgroundColor= Color.FromHex("#DD5500");

                        button.BackgroundColor = Color.FromHex("#DD5500");

                        button.Text = "Blabla";

                        //BoxSEmpty.Clicked += boutonSortir;

                        button.Clicked += async (sender, e) =>

                        {





                            // Ouverture du scan

                            await BtnScanClicked(sender, e);







                        };

                        //Gestion à partir du deuxième stack

                        StckSLayoutMiddle.BackgroundColor = Color.FromHex("#DD7700");

                        LbldAlert.BackgroundColor = Color.FromHex("#641914");

                        LbldAlert.Text = "ALERTE";

                        LblSEnd.BackgroundColor = Color.FromHex("#641914");

                        LblSEnd.Text = "Blabla";

                        // 404 : billet non valide



                        // await this.DisplayAlert("Attention", "Le billet n'est pas valide.", "Cancel");



                        //return;

                    }

                    else if (objresponse.StatusCode == HttpStatusCode.Unauthorized)

                    {

                        popupLoginView.IsVisible = true;

                        //Gestion du premier stack et du bouton

                        StckSLayout.BackgroundColor = Color.FromHex("#DD5500");

                        ImageBack.BackgroundColor = Color.White;

                        //BoxSEmpty.BackgroundColor= Color.FromHex("#DD5500");

                        button.BackgroundColor = Color.FromHex("#DD5500");

                        button.Text = "Blabla";

                        //BoxSEmpty.Clicked += boutonSortir;

                        button.Clicked += async (sender, e) =>

                        {

                            // Ouverture du scan

                            await BtnScanClicked(sender, e);







                        };

                        //Gestion à partir du deuxième stack

                        StckSLayoutMiddle.BackgroundColor = Color.FromHex("#DD7700");

                        LbldAlert.BackgroundColor = Color.FromHex("#641914");

                        LbldAlert.Text = "ALERTE";

                        LblSEnd.BackgroundColor = Color.FromHex("#641914");

                        LblSEnd.Text = "Blabla";

                        // 401 : impossible d'identifier le numéro du billet

                        //  await this.DisplayAlert("Attention", "Impossible d'identifier le numéro du billet, veuillez vérifier les informations de celui ci.", "Cancel");

                        //   return;



                    }

                }

                catch (Exception e)

                {

                    // Erreur

                    await this.DisplayAlert("Attention", e.Message, "Cancel");

                    return;

                }

            }

            else

            {

                // Hors connexion : on vérifie juste si l'utilisateur n'est pas déjà présent dans la table SQL



                // Attention : si pas de prestation : on a le droit d'enregistrer plusieurs fois la présence

                // Si il y a une prestation, en revanche, on doit vérifier qu'il n'est pas déjà inscrit



                if (validate.IdPrestation.HasValue &&

                    validateService.IsInscriptionAlreadyRecorded(validate))

                {

                    popupLoginView.IsVisible = true;



                    //Gestion du premier stack et du bouton

                    StckSLayout.BackgroundColor = Color.FromHex("#DD5500");

                    ImageBack.BackgroundColor = Color.White;

                    //BoxSEmpty.BackgroundColor= Color.FromHex("#DD5500");

                    button.BackgroundColor = Color.FromHex("#DD5500");

                    button.Text = "Blabla";

                    //BoxSEmpty.Clicked += boutonSortir;

                    button.Clicked += async (sender, e) =>

                    {





                        // Ouverture du scan

                        await BtnScanClicked(sender, e);







                    };

                    //Gestion à partir du deuxième stack

                    StckSLayoutMiddle.BackgroundColor = Color.FromHex("#DD7700");

                    LbldAlert.BackgroundColor = Color.FromHex("#641914");

                    LbldAlert.Text = "ALERTE";

                    LblSEnd.BackgroundColor = Color.FromHex("#641914");

                    LblSEnd.Text = "Blabla";



                    // Déjà trouvé : message d'erreur

                    // await this.DisplayAlert("Attention", "Le participant a déjà été enregistré.", "OK");

                    //

                    // return;





                }



            }

        }

        else

        {

            // Pb à l'insertion des données ??



        }





        return;





    }


The exception is on the line: 



popupLoginView.IsVisible = true;


Sorry it's very hard to explain and i'm not english so i hope somebody understand and help me.
Thanks.






c# xamarin stack qr-code







share|improve this question
























  • On which line does the Exception get thrown?
    – MindSwipe
    Nov 12 '18 at 14:50










  • Seems you were trying to index an object with a value that was not valid. Check your code about list in your project when you scan.
    – Jack Hua - MSFT
    Nov 15 '18 at 8:11










  • The only list i have is my NavigationStack whose become empty just during the scan.
    – Kanok
    Nov 22 '18 at 10:06














0












0








0







I have a problem with the scan in a Xamarin app. It's just difficult to explain. I have 4 pages in my app. My Scan is open with a button in the 4th page. When i used the scan the first time i have no problem. As Long as stay on the 4th page i have no problem i can do a lot of scan with no error. But when i use the button Go Back in my app and i go on the 3th page and after i return to the 4th page and i used the scan i have an error.



System.ArgumentOutOfRangeException: Index was out of range. Must be non-negative and less than the size of the collection.

Parameter name: index


At this moment my navigationStack is equal to 0.



My method GoBack just do:




Navigation.PopAsync();




And the scanner bug when i scan my QRCode and i call SendPresenceAck()



private async Task SendPresenceAck(string paramA09) //, int? idPrestation)

    {



        int idParticipant;

        if (!int.TryParse(paramA09, out idParticipant))

        {

            //await this.ShowAlert("Attention", "Problème de lecture du QR Code.");

            await this.DisplayAlert("Attention", "Problème de lecture du QR Code.", "Cancel");



            return;

        }



        // On appelle le WS pour signifier la présence

        // On passe par validateService

        // On prépare la validation de la présence

        var validateService = new ValidatePresenceService(this.Token);



        // On ajoute la ligne à valider

        var validate = validateService.AddNewPresence(idParticipant, this.idPrestation, true);



        // On déclenche l'envoi au WS (si besoin)

        if (validate != null)

        {

            // On envoie uniquement en cas de connexion

            if (!Global.GetSettingsBool(TypeSettings.IsHorsConnexion))

            {

                //await validateService.SendAll();

                // Attention : si participant déjà enregistré : erreur 403

                try

                {

                    await validateService.Send(validate);

                    // await this.DisplayAlert("OK", "Le billet est validé.", "OK");

                    popupLoginView.IsVisible = true;

                    //Gestion du premier stack et du bouton

                    StckSLayout.BackgroundColor = Color.FromHex("#DD5500");

                    ImageBack.BackgroundColor = Color.White;

                    //BoxSEmpty.BackgroundColor= Color.FromHex("#DD5500");

                    button.BackgroundColor = Color.FromHex("#DD5500");

                    button.Text = "Blabla";

                    //BoxSEmpty.Clicked += boutonSortir;

                    button.Clicked += async (sender, e) =>

                    {

                        // Ouverture du scan

                        await BtnScanClicked(sender, e);







                    };

                    //Gestion à partir du deuxième stack

                    StckSLayoutMiddle.BackgroundColor = Color.FromHex("#DD7700");

                    LbldAlert.BackgroundColor = Color.FromHex("#641914");

                    LbldAlert.Text = "ALERTE";

                    LblSEnd.BackgroundColor = Color.FromHex("#641914");

                    LblSEnd.Text = "Blabla";

                    // 401 : impossible d'identifier le numéro du billet

                    //  await this.DisplayAlert("Attention", "Impossible d'identifier le numéro du billet, veuillez vérifier les informations de celui ci.", "Cancel");

                    //   return;







                }

                catch (WebException ex)

                {

                    HttpWebResponse objresponse = ex.Response as HttpWebResponse;

                    if (objresponse.StatusCode == HttpStatusCode.Forbidden)

                    {

                        popupLoginView.IsVisible = true;

                        //Gestion du premier stack et du bouton

                        StckSLayout.BackgroundColor = Color.FromHex("#DD5500");

                        ImageBack.BackgroundColor = Color.White;

                        //BoxSEmpty.BackgroundColor= Color.FromHex("#DD5500");

                        button.BackgroundColor = Color.FromHex("#DD5500");

                        button.Text = "Blabla";

                        //BoxSEmpty.Clicked += boutonSortir;

                        button.Clicked += async (sender, e) =>

                        {

                            // Ouverture du scan

                            await BtnScanClicked(sender, e);







                        };

                        //Gestion à partir du deuxième stack

                        StckSLayoutMiddle.BackgroundColor = Color.FromHex("#DD7700");

                        LbldAlert.BackgroundColor = Color.FromHex("#641914");

                        LbldAlert.Text = "ALERTE";

                        LblSEnd.BackgroundColor = Color.FromHex("#641914");

                        LblSEnd.Text = "Blabla";

                        // 403 : le participant a déjà été enregistré aujourd'hui

                        // Message d'erreur

                        // await this.DisplayAlert("Attention", "Le billet a déjà été enregistré, le numéro du billet a déjà été scanné auparavant.", "OK");

                        // return;



                    }

                    else if (objresponse.StatusCode == HttpStatusCode.NotFound)

                    {

                        popupLoginView.IsVisible = true;

                        //Gestion du premier stack et du bouton

                        StckSLayout.BackgroundColor = Color.FromHex("#DD5500");

                        ImageBack.BackgroundColor = Color.White;

                        //BoxSEmpty.BackgroundColor= Color.FromHex("#DD5500");

                        button.BackgroundColor = Color.FromHex("#DD5500");

                        button.Text = "Blabla";

                        //BoxSEmpty.Clicked += boutonSortir;

                        button.Clicked += async (sender, e) =>

                        {





                            // Ouverture du scan

                            await BtnScanClicked(sender, e);







                        };

                        //Gestion à partir du deuxième stack

                        StckSLayoutMiddle.BackgroundColor = Color.FromHex("#DD7700");

                        LbldAlert.BackgroundColor = Color.FromHex("#641914");

                        LbldAlert.Text = "ALERTE";

                        LblSEnd.BackgroundColor = Color.FromHex("#641914");

                        LblSEnd.Text = "Blabla";

                        // 404 : billet non valide



                        // await this.DisplayAlert("Attention", "Le billet n'est pas valide.", "Cancel");



                        //return;

                    }

                    else if (objresponse.StatusCode == HttpStatusCode.Unauthorized)

                    {

                        popupLoginView.IsVisible = true;

                        //Gestion du premier stack et du bouton

                        StckSLayout.BackgroundColor = Color.FromHex("#DD5500");

                        ImageBack.BackgroundColor = Color.White;

                        //BoxSEmpty.BackgroundColor= Color.FromHex("#DD5500");

                        button.BackgroundColor = Color.FromHex("#DD5500");

                        button.Text = "Blabla";

                        //BoxSEmpty.Clicked += boutonSortir;

                        button.Clicked += async (sender, e) =>

                        {

                            // Ouverture du scan

                            await BtnScanClicked(sender, e);







                        };

                        //Gestion à partir du deuxième stack

                        StckSLayoutMiddle.BackgroundColor = Color.FromHex("#DD7700");

                        LbldAlert.BackgroundColor = Color.FromHex("#641914");

                        LbldAlert.Text = "ALERTE";

                        LblSEnd.BackgroundColor = Color.FromHex("#641914");

                        LblSEnd.Text = "Blabla";

                        // 401 : impossible d'identifier le numéro du billet

                        //  await this.DisplayAlert("Attention", "Impossible d'identifier le numéro du billet, veuillez vérifier les informations de celui ci.", "Cancel");

                        //   return;



                    }

                }

                catch (Exception e)

                {

                    // Erreur

                    await this.DisplayAlert("Attention", e.Message, "Cancel");

                    return;

                }

            }

            else

            {

                // Hors connexion : on vérifie juste si l'utilisateur n'est pas déjà présent dans la table SQL



                // Attention : si pas de prestation : on a le droit d'enregistrer plusieurs fois la présence

                // Si il y a une prestation, en revanche, on doit vérifier qu'il n'est pas déjà inscrit



                if (validate.IdPrestation.HasValue &&

                    validateService.IsInscriptionAlreadyRecorded(validate))

                {

                    popupLoginView.IsVisible = true;



                    //Gestion du premier stack et du bouton

                    StckSLayout.BackgroundColor = Color.FromHex("#DD5500");

                    ImageBack.BackgroundColor = Color.White;

                    //BoxSEmpty.BackgroundColor= Color.FromHex("#DD5500");

                    button.BackgroundColor = Color.FromHex("#DD5500");

                    button.Text = "Blabla";

                    //BoxSEmpty.Clicked += boutonSortir;

                    button.Clicked += async (sender, e) =>

                    {





                        // Ouverture du scan

                        await BtnScanClicked(sender, e);







                    };

                    //Gestion à partir du deuxième stack

                    StckSLayoutMiddle.BackgroundColor = Color.FromHex("#DD7700");

                    LbldAlert.BackgroundColor = Color.FromHex("#641914");

                    LbldAlert.Text = "ALERTE";

                    LblSEnd.BackgroundColor = Color.FromHex("#641914");

                    LblSEnd.Text = "Blabla";



                    // Déjà trouvé : message d'erreur

                    // await this.DisplayAlert("Attention", "Le participant a déjà été enregistré.", "OK");

                    //

                    // return;





                }



            }

        }

        else

        {

            // Pb à l'insertion des données ??



        }





        return;





    }


The exception is on the line: 



popupLoginView.IsVisible = true;


Sorry it's very hard to explain and i'm not english so i hope somebody understand and help me.
Thanks.






c# xamarin stack qr-code







share|improve this question















I have a problem with the scan in a Xamarin app. It's just difficult to explain. I have 4 pages in my app. My Scan is open with a button in the 4th page. When i used the scan the first time i have no problem. As Long as stay on the 4th page i have no problem i can do a lot of scan with no error. But when i use the button Go Back in my app and i go on the 3th page and after i return to the 4th page and i used the scan i have an error.



System.ArgumentOutOfRangeException: Index was out of range. Must be non-negative and less than the size of the collection.

Parameter name: index


At this moment my navigationStack is equal to 0.



My method GoBack just do:




Navigation.PopAsync();




And the scanner bug when i scan my QRCode and i call SendPresenceAck()



private async Task SendPresenceAck(string paramA09) //, int? idPrestation)

    {



        int idParticipant;

        if (!int.TryParse(paramA09, out idParticipant))

        {

            //await this.ShowAlert("Attention", "Problème de lecture du QR Code.");

            await this.DisplayAlert("Attention", "Problème de lecture du QR Code.", "Cancel");



            return;

        }



        // On appelle le WS pour signifier la présence

        // On passe par validateService

        // On prépare la validation de la présence

        var validateService = new ValidatePresenceService(this.Token);



        // On ajoute la ligne à valider

        var validate = validateService.AddNewPresence(idParticipant, this.idPrestation, true);



        // On déclenche l'envoi au WS (si besoin)

        if (validate != null)

        {

            // On envoie uniquement en cas de connexion

            if (!Global.GetSettingsBool(TypeSettings.IsHorsConnexion))

            {

                //await validateService.SendAll();

                // Attention : si participant déjà enregistré : erreur 403

                try

                {

                    await validateService.Send(validate);

                    // await this.DisplayAlert("OK", "Le billet est validé.", "OK");

                    popupLoginView.IsVisible = true;

                    //Gestion du premier stack et du bouton

                    StckSLayout.BackgroundColor = Color.FromHex("#DD5500");

                    ImageBack.BackgroundColor = Color.White;

                    //BoxSEmpty.BackgroundColor= Color.FromHex("#DD5500");

                    button.BackgroundColor = Color.FromHex("#DD5500");

                    button.Text = "Blabla";

                    //BoxSEmpty.Clicked += boutonSortir;

                    button.Clicked += async (sender, e) =>

                    {

                        // Ouverture du scan

                        await BtnScanClicked(sender, e);







                    };

                    //Gestion à partir du deuxième stack

                    StckSLayoutMiddle.BackgroundColor = Color.FromHex("#DD7700");

                    LbldAlert.BackgroundColor = Color.FromHex("#641914");

                    LbldAlert.Text = "ALERTE";

                    LblSEnd.BackgroundColor = Color.FromHex("#641914");

                    LblSEnd.Text = "Blabla";

                    // 401 : impossible d'identifier le numéro du billet

                    //  await this.DisplayAlert("Attention", "Impossible d'identifier le numéro du billet, veuillez vérifier les informations de celui ci.", "Cancel");

                    //   return;







                }

                catch (WebException ex)

                {

                    HttpWebResponse objresponse = ex.Response as HttpWebResponse;

                    if (objresponse.StatusCode == HttpStatusCode.Forbidden)

                    {

                        popupLoginView.IsVisible = true;

                        //Gestion du premier stack et du bouton

                        StckSLayout.BackgroundColor = Color.FromHex("#DD5500");

                        ImageBack.BackgroundColor = Color.White;

                        //BoxSEmpty.BackgroundColor= Color.FromHex("#DD5500");

                        button.BackgroundColor = Color.FromHex("#DD5500");

                        button.Text = "Blabla";

                        //BoxSEmpty.Clicked += boutonSortir;

                        button.Clicked += async (sender, e) =>

                        {

                            // Ouverture du scan

                            await BtnScanClicked(sender, e);







                        };

                        //Gestion à partir du deuxième stack

                        StckSLayoutMiddle.BackgroundColor = Color.FromHex("#DD7700");

                        LbldAlert.BackgroundColor = Color.FromHex("#641914");

                        LbldAlert.Text = "ALERTE";

                        LblSEnd.BackgroundColor = Color.FromHex("#641914");

                        LblSEnd.Text = "Blabla";

                        // 403 : le participant a déjà été enregistré aujourd'hui

                        // Message d'erreur

                        // await this.DisplayAlert("Attention", "Le billet a déjà été enregistré, le numéro du billet a déjà été scanné auparavant.", "OK");

                        // return;



                    }

                    else if (objresponse.StatusCode == HttpStatusCode.NotFound)

                    {

                        popupLoginView.IsVisible = true;

                        //Gestion du premier stack et du bouton

                        StckSLayout.BackgroundColor = Color.FromHex("#DD5500");

                        ImageBack.BackgroundColor = Color.White;

                        //BoxSEmpty.BackgroundColor= Color.FromHex("#DD5500");

                        button.BackgroundColor = Color.FromHex("#DD5500");

                        button.Text = "Blabla";

                        //BoxSEmpty.Clicked += boutonSortir;

                        button.Clicked += async (sender, e) =>

                        {





                            // Ouverture du scan

                            await BtnScanClicked(sender, e);







                        };

                        //Gestion à partir du deuxième stack

                        StckSLayoutMiddle.BackgroundColor = Color.FromHex("#DD7700");

                        LbldAlert.BackgroundColor = Color.FromHex("#641914");

                        LbldAlert.Text = "ALERTE";

                        LblSEnd.BackgroundColor = Color.FromHex("#641914");

                        LblSEnd.Text = "Blabla";

                        // 404 : billet non valide



                        // await this.DisplayAlert("Attention", "Le billet n'est pas valide.", "Cancel");



                        //return;

                    }

                    else if (objresponse.StatusCode == HttpStatusCode.Unauthorized)

                    {

                        popupLoginView.IsVisible = true;

                        //Gestion du premier stack et du bouton

                        StckSLayout.BackgroundColor = Color.FromHex("#DD5500");

                        ImageBack.BackgroundColor = Color.White;

                        //BoxSEmpty.BackgroundColor= Color.FromHex("#DD5500");

                        button.BackgroundColor = Color.FromHex("#DD5500");

                        button.Text = "Blabla";

                        //BoxSEmpty.Clicked += boutonSortir;

                        button.Clicked += async (sender, e) =>

                        {

                            // Ouverture du scan

                            await BtnScanClicked(sender, e);







                        };

                        //Gestion à partir du deuxième stack

                        StckSLayoutMiddle.BackgroundColor = Color.FromHex("#DD7700");

                        LbldAlert.BackgroundColor = Color.FromHex("#641914");

                        LbldAlert.Text = "ALERTE";

                        LblSEnd.BackgroundColor = Color.FromHex("#641914");

                        LblSEnd.Text = "Blabla";

                        // 401 : impossible d'identifier le numéro du billet

                        //  await this.DisplayAlert("Attention", "Impossible d'identifier le numéro du billet, veuillez vérifier les informations de celui ci.", "Cancel");

                        //   return;



                    }

                }

                catch (Exception e)

                {

                    // Erreur

                    await this.DisplayAlert("Attention", e.Message, "Cancel");

                    return;

                }

            }

            else

            {

                // Hors connexion : on vérifie juste si l'utilisateur n'est pas déjà présent dans la table SQL



                // Attention : si pas de prestation : on a le droit d'enregistrer plusieurs fois la présence

                // Si il y a une prestation, en revanche, on doit vérifier qu'il n'est pas déjà inscrit



                if (validate.IdPrestation.HasValue &&

                    validateService.IsInscriptionAlreadyRecorded(validate))

                {

                    popupLoginView.IsVisible = true;



                    //Gestion du premier stack et du bouton

                    StckSLayout.BackgroundColor = Color.FromHex("#DD5500");

                    ImageBack.BackgroundColor = Color.White;

                    //BoxSEmpty.BackgroundColor= Color.FromHex("#DD5500");

                    button.BackgroundColor = Color.FromHex("#DD5500");

                    button.Text = "Blabla";

                    //BoxSEmpty.Clicked += boutonSortir;

                    button.Clicked += async (sender, e) =>

                    {





                        // Ouverture du scan

                        await BtnScanClicked(sender, e);







                    };

                    //Gestion à partir du deuxième stack

                    StckSLayoutMiddle.BackgroundColor = Color.FromHex("#DD7700");

                    LbldAlert.BackgroundColor = Color.FromHex("#641914");

                    LbldAlert.Text = "ALERTE";

                    LblSEnd.BackgroundColor = Color.FromHex("#641914");

                    LblSEnd.Text = "Blabla";



                    // Déjà trouvé : message d'erreur

                    // await this.DisplayAlert("Attention", "Le participant a déjà été enregistré.", "OK");

                    //

                    // return;





                }



            }

        }

        else

        {

            // Pb à l'insertion des données ??



        }





        return;





    }


The exception is on the line: 



popupLoginView.IsVisible = true;


Sorry it's very hard to explain and i'm not english so i hope somebody understand and help me.
Thanks.






c# xamarin stack qr-code




c# xamarin stack qr-code






share|improve this question















share|improve this question













share|improve this question




share|improve this question








edited Nov 12 '18 at 14:57

























asked Nov 12 '18 at 14:45









Kanok

33




33












  • On which line does the Exception get thrown?
    – MindSwipe
    Nov 12 '18 at 14:50










  • Seems you were trying to index an object with a value that was not valid. Check your code about list in your project when you scan.
    – Jack Hua - MSFT
    Nov 15 '18 at 8:11










  • The only list i have is my NavigationStack whose become empty just during the scan.
    – Kanok
    Nov 22 '18 at 10:06


















  • On which line does the Exception get thrown?
    – MindSwipe
    Nov 12 '18 at 14:50










  • Seems you were trying to index an object with a value that was not valid. Check your code about list in your project when you scan.
    – Jack Hua - MSFT
    Nov 15 '18 at 8:11










  • The only list i have is my NavigationStack whose become empty just during the scan.
    – Kanok
    Nov 22 '18 at 10:06
















On which line does the Exception get thrown?
– MindSwipe
Nov 12 '18 at 14:50




On which line does the Exception get thrown?
– MindSwipe
Nov 12 '18 at 14:50












Seems you were trying to index an object with a value that was not valid. Check your code about list in your project when you scan.
– Jack Hua - MSFT
Nov 15 '18 at 8:11




Seems you were trying to index an object with a value that was not valid. Check your code about list in your project when you scan.
– Jack Hua - MSFT
Nov 15 '18 at 8:11












The only list i have is my NavigationStack whose become empty just during the scan.
– Kanok
Nov 22 '18 at 10:06




The only list i have is my NavigationStack whose become empty just during the scan.
– Kanok
Nov 22 '18 at 10:06












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