What is the best back-end web development language?

I am adding some data to API. But I am getting an error Newtonsoft.Json.JsonReaderException: ..
While debugging in response variable I am getting {StatusCode: 500, ReasonPhrase: 'Internal Server Error', Version: 1.1, Content: System.Net.Http.StreamContent, Headers:
{
Cache-Control: no-cache, private
Connection: close
Content-Type: text/html; charset=UTF-8
}}
As i am getting response in html format instead of json . I am unable to deserialize....Any suggestion plz.. where I am doing wrong?

public class StatusView
{
public string status { get; set; }
}

class AddBillFun
{
    public async static Task<StatusView> AddBillData(string transaction_date1, string billing_date1, string vehicle_id1, string customer_id1, string fuel_id1
                                               , string fuel_unit_id1, string fuel_price_id1, string price_per_unit1, string quantity1, string amount1
                                               , string recieved_amount1, string advanced_amount1, string net_amount1, string _status1, string station_id1)
    {

        StatusView statusCheck = new StatusView();
         Uri uri = new Uri(Constants.Bills_URL);
        var postData = new List<KeyValuePair<string, string>>
            {
                new KeyValuePair<string, string>("transaction_date",transaction_date1),//"2018-10-05 12:16:11"
                new KeyValuePair<string, string>("billing_date",billing_date1 ),//"2018-10-05"
                new KeyValuePair<string, string>("vehicle_id",vehicle_id1),//"1"
                new KeyValuePair<string, string>("customer_id", customer_id1),//"1"
                new KeyValuePair<string, string>("fuel_id",fuel_id1),//"1"
                new KeyValuePair<string, string>("fuel_unit_id",fuel_unit_id1 ),//"1"
                new KeyValuePair<string, string>("fuel_price_id",fuel_price_id1 ),//""
                new KeyValuePair<string, string>("price_per_unit",price_per_unit1 ),//"70"
                new KeyValuePair<string, string>("quantity", quantity1),//"10"
                new KeyValuePair<string, string>("amount",amount1 ),//"700"
                new KeyValuePair<string, string>("received_amount",recieved_amount1 ),//"0"
                new KeyValuePair<string, string>("advance_amount", advanced_amount1 ),//"0"
                new KeyValuePair<string, string>("net_amount",net_amount1 ),//"700"
                new KeyValuePair<string, string>("status",_status1 ),//"success"
                new KeyValuePair<string, string>("station_id",station_id1 )//"1"

            };

        HttpRequestMessage req = new HttpRequestMessage(HttpMethod.Post, uri);
        req.Content = new FormUrlEncodedContent(postData);

        using (HttpClient client = new HttpClient())
        {
            var response = await client.SendAsync(req);

            var content = await response.Content.ReadAsStringAsync();

            statusCheck = JsonConvert.DeserializeObject<StatusView>(content);
        }

        return statusCheck;

    }
}

I am using following code for DL scan. DL scan is not working.

 var options = new MobileBarcodeScanningOptions
          {
            AutoRotate = false,
            UseFrontCameraIfAvailable = false,
            TryHarder = true,
             CameraResolutionSelector = HandleCameraResolutionSelectorDelegate,
              PossibleFormats = new List<BarcodeFormat> { BarcodeFormat.PDF_417 }
           };

   var QRScanner = new ZXingScannerPage(options);

   await Application.Current.MainPage.Navigation.PushAsync(QRScanner);

   CameraResolution HandleCameraResolutionSelectorDelegate(List<CameraResolution> availableResolutions)
     {
                        //Don't know if this will ever be null or empty
                        if (availableResolutions == null || availableResolutions.Count < 1)
                            return new CameraResolution() { Width = 800, Height = 600 };

                        return FindHighestResolution(availableResolutions);
    }

   private CameraResolution FindHighestResolution(List<CameraResolution> availableResolutions)
    {
            CameraResolution max = availableResolutions[0];
             foreach(CameraResolution cameraResolution in availableResolutions)
                {
                            if (max.Width < cameraResolution.Width)
                            {
                                max = cameraResolution;
                            }
                }
               return max;
     }

please help. Thanks in advance.

Hello dear Xamariners !

I'm wasting a lot of time trying to figure out why FontAwesome doesn't work on Android & iOS.
No need to tell you that I've tried several solutions I found on this forum.

To help you to help me (what ? haha)
Here are some screenshots :

On iOS :

On UWP or Android (kind of same result I don't have the right icon)

The FontFamily resource in app.xaml :

My Fonts folder :

My VS fonts Android folder with the properties AndroidAsset // copy if newer

My VS fonts UWP folder with the properties Content // Do not copy

Do you have any idea why it isn't working ?

I've tried several way to declare my font (without the otf.#name of font , with .otf#name of font style , with .otf only)

If anybody got this working, it would be awesome to get some help.
PS : I'd like to avoid a custom renderer

I wish you all a good weekend !

I have a button and web view in the page. On click of button i need to run a external JavaScript function on web view(html content). Javascript is not linked to html page anywhere, ts separate file. Any suggestions how to achieve the same.

Hi,

I have seen sqlite but I am asking what if I want a simple local storage just to save one variable user_id to determine the user ID?

What's the best way yo do it so even if the user closes the app or the phone it will still be stored?

Kindly advise...

Thanks,
Jassim

I was trying to build an app in release configuration, but I'm getting an error

I don't have the reference to System.Web in my project. The only file that contains "system.web" text is machine.config file in the app bundle

Hey you guys,

I made an application to read some QR Codes using Zxing on Xamarin. Days before yesterday, it was working good, but since yesterday I have this problem:

I put a breakpoint in OnAppearing() method, but it's ignored, Ok... When I click in the Zxing button, to open the scanner, the application stops, but don't show nothing, only freeze, no errors, no messages, no debug, nothing. My code is the same as when it was working, nothing changed. If anybody could help me, I'll be grateful.

Thanks

I have a button that is centered, and when a entry is set to visible - the button is pushed sideways. Right now the motion happens to quickly - is there anyway I can slow the motion down?

Severity Code Description Project File Line Suppression State
Warning NU1701 Package 'Newtonsoft.Json 8.0.3' was restored using '.NETFramework,Version=v4.6.1' instead of the project target framework '.NETStandard,Version=v2.0'. This package may not be fully compatible with your project. test C:\Users\ssc\source\repos\test\test\test\test.csproj 1

We've found some rather annoying issues with multiple taps and navigation on Android using Xamarin.Forms. Let's say there's a button press and in the handler there's a bog-standard await Navigation.PushAsync(new SomePage()).

If you're really fast, you can tap the button multiple times, pushing multiple pages on to the stack.

This class of bug also happens when dismissing pages. Suppose you have a button with a handler with an await Navigation.PopAsync(). If you're really fast, you can multiple-tap that button as it animates away; in our test cases, this often caused a crash mentioning jobject being equal to IntPtr.Zero or something.

We've managed limited mitigation by storing a time-of-last-tap and swallowing excess taps within a certain threshold of the previous successful tap, but this seems very kludgey...

Ideally pages should not respond to touch events unless they're the top page on the navigation stack and there's no page-related animation happening. Is there a good general solution to this?

By the way, you can see this in the Xamarin Evolve app. Go to a session, multi-tap Send Feedback, and watch a bunch of feedback windows push onto the stack. Or multi-tap Cancel and watch a bunch of them dismiss. (In this case it doesn't seem to crash.)

Hello there!

I have some commands on my ViewModels, and I realized that I can them multiple times at the same time, and is getting me some troubles with updating data from a WebApi.

The basic structure I have is something like:

        private Command _LoadCommand;
        public Command LoadCommand
        {
            get { return _LoadCommand ?? (_LoadCommand = new Command(async() => await ExecuteLoad())); }
        }

        private async Task ExecuteLoad ()
        {
                IsBusy = true;
                SendSignatureToSAP.ChangeCanExecute();

                await DoSomething();

                SendSignatureToSAP.ChangeCanExecute();
                IsBusy = false;
        }

I read about ChangeCanExecute and some documentation about Commands. It doesn't reccoment to call CanExecute(false) because it doesn't trigger an event or something like that. Also, I read that since a not-so-recent version of XF, it can have the value "null" and ChangeCanExecute only puts it into null again, but I don't know if this is true or if it makes sense.

So, what should I do to know if it's doing it right or not?
It's also allowing pages to trigger OnSizeAllocated when I'm in a child page, atop of it.

Thank you!

I am a real beginner in cross-platform programming, .NET and C#.

I wrote a simple program, at the end it should pop up a window about who won the game. I'm using XAML with MVVM, I have an event in the model which gives back the winner. I did all the bindings in the XAML file, the app.cs has a private async void function which I think doesn't work for some reason.
It looks kinda like this:

    private async void GameOver(object sender, modelEvent e)
            {
                if (e.result == 0)
                {
                     await MainPage.DisplayAlert("Game", "Drawn!",
                                                "OK");
                }
                if (e.result == 1)
                {
                     await MainPage.DisplayAlert("Game", "First player won!",
                                                "OK");
                }
                if (e.result == 2) 
                {
                     await MainPage.DisplayAlert("Game", "Second player won!",
                                                "OK");
                }

            }

What might be the problem here?

Hello,

i need to create app which needs to use wi-fi network which has no internet. I found possibility to do it using connectivitymanager and network callback, but I found code only in Java and I have really problem to implement in C# NetworkCallback with OnAvailable method inside.

connectivityManager.requestNetwork(builder.build(), new ConnectivityManager.NetworkCallback() {
     @Override
     public void onAvailable(Network network) {
        if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.M) {
            if (Build.VERSION.RELEASE.equalsIgnoreCase("6.0")) {
               if (!Settings.System.canWrite(mActivity)) {
                      Intent goToSettings = new Intent(Settings.ACTION_MANAGE_WRITE_SETTINGS);
                      goToSettings.setData(Uri.parse("package:" + mActivity.getPackageName()));
                      mActivity.startActivity(goToSettings);
                }
             }

             connectivityManager.bindProcessToNetwork(null);

       if (mSsid.contains("my_iot_device-xxxxxxxxx")) {
            connectivityManager.bindProcessToNetwork(network);
       }
}

I know, it should be managed somehow using delegates and events in C#, but I am not really sure how. Do you have any ideas how to implements this NetworkCallback with method inside? Is there any other possibility how to accomplish this task?

Hi,

Somehow I managed to save the wrong keystore for my Android app that I developed using Xamarin and already published.
When I wanted to upload an update to the Google Play Store with the keystore that I thought was the right keystore,
the SHA certificate did not match.

Luckily I was registered for Google Play App Signing so they were able to reset the Upload Key for me.
In order to reset the upload key I:

1. (dont know if i had to do this to generate new upload key) Generated a new archive and new keystore for the Android project in Xamarin and exported the APK to a folder. In that folder i ran the command lines in the next steps:

2. Generated a new upload key using the command line:
   keytool -genkeypair -alias upload -keyalg RSA -keysize 2048 -validity 9125 -keystore keystore.jks

3. Exported the certificate for that key to a *.pem file:
   keytool -export -rfc -alias upload -file upload_certificate.pem -keystore keystore.jks

4. Sent the *.pem to Google Play Developer Support.**

   Now that I have a *.pem file and *.jks file, how do I create the new APK file for my Xamarin Android project, signed with the new upload key in Visual Studio?

Hi.
I Have 1 problem.

I have ContentPage.

In the start of this page i have Image element and another content in stack layout etc...
All content inside Scroll View

Now I want to catch, when user scroll down, and when IMAGE NO DISPLAY to user.

What is th e best way to catch that user doesn`t see the Image???

Hi I am currently having an issue when trying to share a file using a FileProvider.

In all but one test instance, the file is not available to the application selected from the chooser intent. Running the test, that was enable to attach the pdf document to an email, is now also failing.

Further to this, if Gmail is selected as the share destination and an email sent, the body of the email has appended to it, this is not in the value that is added to the intent with the ExtraText flag.

I have checked the file that is being tested, and it is a valid PDF file.

From stepping through the code I am able to see that the file is in the files/pdf directory on the device.

The canonical file path is:
/data/data/com.myapp.identity/files/pdf/testdocument.pdf.

The absolute file path is :
/data/user/0/com.myapp.identity/files/pdf/testdocument.pdf

The following is the contents of the providers file

<?xml version="1.0" encoding="utf-8"?>
<paths xmlns:android="...">
    <files-path name="pdfshare" path="./pdf" />
</paths>

The following is the method used for sharing the file.

public Task Show(string title, string message, string filePath)
{
    //  Create a Java file instance, to be used by the file provider and check that the file exists
    var pdfFile = new Java.IO.File(filePath);
    if (!pdfFile.Exists())
    {
        //  The file that is being shared does not exist so throw an exception
        throw new Exception("Unable to share file; File does not exist at specified path");
    }

    //  Get a URI for the file from the file provider to enable sharing
    var pdfUri = FileProvider.GetUriForFile(CrossCurrentActivity.Current.Activity, AUTHORITY, pdfFile);
    //  Get the mime type for the URI
    var mimeType = CrossCurrentActivity.Current.Activity.ContentResolver.GetType(pdfUri);
    //  Create the intent for the chooser with the required permissions
    var intent = new Intent();
    intent.SetAction(Intent.ActionSend);
    intent.AddFlags(ActivityFlags.GrantReadUriPermission);
    //  Add the PDF to the intent and set the mime type for the data
    intent.PutExtra(Intent.ExtraStream, pdfUri);
    intent.SetType(mimeType);
    //  Add the additional details to the intent, incase email is selected
    intent.PutExtra(Intent.ExtraSubject, title ?? SHARE_SUBJECT);
    intent.PutExtra(Intent.ExtraText, message ?? DEFAULT_TEXT);
    // Create and display the native chooser for the user to select an app from
    var chooserIntent = Intent.CreateChooser(intent, "Select App to share file");
    chooserIntent.SetFlags(ActivityFlags.ClearTop  | ActivityFlags.NewTask);
    CrossCurrentActivity.Current.Activity.StartActivity(chooserIntent);

    return Task.FromResult(true);
}

I am currently unable to determine why this code is failing to enable the file to be accessed by the selected application.

I also get the same result if I use ShareCompat.

Can anyone help?

Thank you.

I want to building apps "fastly". IOS not importand for me.
Which one i must use? xamarin.android or xamarin.forms ?

Which one is easyer?

Greetings everyone, I'm having a problem when my Label binded with the text "displayString" inside the listview stacklayout is too large and breaks the line, expanding the column it belongs, its shown in the image below:

Here is the code of the ListView, have anyone faced this problem before?

<ListView
                x:Name="MyListView"
                Margin="5,0,0,0"
                CachingStrategy="RecycleElement"
                HasUnevenRows="True"
                IsGroupingEnabled="false"
                ItemsSource="{Binding DevicesList, Mode=TwoWay}"
                RowHeight="60">
                <ListView.Behaviors>
                    <local1:ListViewTappedItemBehavior Command="{Binding DeviceTappedCommand}" Converter="{StaticResource SelectedItemConverter}" />
                </ListView.Behaviors>
                <ListView.ItemTemplate>
                    <DataTemplate>
                        <ViewCell>
                            <!--<ViewCell.ContextActions>
                                <MenuItem
                                    Command="{Binding Path=BindingContext.ShareDeviceCommand, Source={x:Reference Name=MyListView}}"
                                    CommandParameter="{Binding .}"
                                    Text="Compartilhar" />
                                <MenuItem
                                    Command="{Binding Path=BindingContext.RemoveDeviceCommand, Source={x:Reference Name=MyListView}}"
                                    CommandParameter="{Binding .}"
                                    IsDestructive="True"
                                    Text="Excluir" />
                            </ViewCell.ContextActions>-->
                            <ViewCell.View>
                                <StackLayout HorizontalOptions="StartAndExpand" Orientation="Horizontal">
                                    <Grid>
                                        <Grid.ColumnDefinitions>
                                            <ColumnDefinition Width="4*" />
                                            <ColumnDefinition Width="20*" />
                                            <ColumnDefinition Width="4*" />
                                            <ColumnDefinition Width="4*" />
                                        </Grid.ColumnDefinitions>
                                        <Image
                                            Grid.Column="0"
                                            Aspect="AspectFill"
                                            HeightRequest="50"
                                            Source="{Binding ImageResourceId}"
                                            VerticalOptions="Center" />
                                        <StackLayout Grid.Column="1" Orientation="Vertical">
                                            <Label
                                                FontAttributes="Bold"
                                                FontSize="Large"
                                                Text="{Binding name}"
                                                TextColor="Black" />
                                            <Label
                                                FontSize="Medium"
                                                Text="{Binding displayString}"
                                                TextColor="Black" />
                                        </StackLayout>
                                        <Image
                                            Grid.Column="2"
                                            HeightRequest="50"
                                            HorizontalOptions="EndAndExpand"
                                            Scale="1.2"
                                            Source="acceptShareIcon.png"
                                            VerticalOptions="Center">
                                            <Image.GestureRecognizers>
                                                <TapGestureRecognizer Command="{Binding Path=BindingContext.AcceptShareCommand, Source={x:Reference MyListView}}" CommandParameter="{Binding .}" />
                                            </Image.GestureRecognizers>
                                        </Image>
                                        <Image
                                            Grid.Column="3"
                                            HeightRequest="50"
                                            HorizontalOptions="EndAndExpand"
                                            Scale="1.2"
                                            Source="declineShareIcon.png"
                                            VerticalOptions="Center">
                                            <Image.GestureRecognizers>
                                                <TapGestureRecognizer Command="{Binding Path=BindingContext.DeclineShareCommand, Source={x:Reference MyListView}}" CommandParameter="{Binding .}" />
                                            </Image.GestureRecognizers>
                                        </Image>
                                    </Grid>
                                </StackLayout>
                            </ViewCell.View>
                        </ViewCell>
                    </DataTemplate>
                </ListView.ItemTemplate>
            </ListView>

how to display .gif image as launch screen(splash screen) in xamarin forms ios.i have idea in xamarin forms android but i don't have idea in ios.please share with me if any one have idea