Develop Reference

UWP SharpCompress Access Exception On Local Drives, Why?

I'm trying to use SharpCompress to read .rar files from my UWP application. It works fine on network shares from which I can read the archive no problem, but I get System.UnauthorizedAccessException on files anywhere on the local system including for instance USB drives. I have access to the files by other methods e.g. StorageFile. It makes no difference whether BroadFileSystemAccess is on or off. I've tried in both C# and Vb.net Here's the code of my test app in C#. The exception occurs at ArchiveFactory.Open.
I can also read Zip files no problem using the .net Compression methods but they can't do rar files, hence needing SharpCompress.
using System;
using System.IO;
using Windows.UI.Xaml;
using Windows.UI.Xaml.Controls;
using SharpCompress;
using Windows.Storage.Pickers;
using Windows.Storage;
using SharpCompress.Archives;
namespace TestRAR
{
public sealed partial class MainPage : Page
{
public MainPage()
{
this.InitializeComponent();
OpenRAR.Click += OpenRAR_Clicked;
}
public async void OpenRAR_Clicked(object sender, RoutedEventArgs e)
{
FileOpenPicker picker = new FileOpenPicker();
picker.FileTypeFilter.Add(".rar");
picker.FileTypeFilter.Add(".cbr");
picker.FileTypeFilter.Add(".cbz");
picker.FileTypeFilter.Add(".zip");
StorageFile pickfile = await picker.PickSingleFileAsync();
if (pickfile == null) { return; }
string pth = pickfile.Path;
FileInfo pickInfo = new FileInfo(pth);
try
{
ListRARs.Items.Clear();
using (var Arch = ArchiveFactory.Open(pickInfo))
{
foreach (IArchiveEntry a in Arch.Entries)
{
string thisKey = a.Key;
ListRARs.Items.Add(thisKey);
}
}
}
catch{ }
}
}
}
This is the first time I've used SharpCompress and I'm completely stumped. Any ideas anyone?

Make a USSD call in Xamarin Crossplatform app

I want to make a USSD call in a xamarin crossplatform app using C# and i have no idea where to start. All the examples i have seen is done in java. Is it possible to successfully dial a USSD code like *270# within my app without opening the dialer? If yes, please how? I'll be very grateful for any help

To do it with Xamarin forms you have to create a custom renderer for android :
Create an interface in your shared project :
public interface IUssdRenderer
{
void StartTransaction();
}
then in your android project :
using System;
using Android.Content;
using Android.OS;
using ussd.Renderers;
[assembly: Xamarin.Forms.Dependency(typeof(IUssdRenderer))]
namespace ussd.Droid.Renderers
{
public class UssdRenderer : IUssdRenderer
{
public Android.Net.Uri createUriFromString(string ussd)
{
String uri = "tel:";
foreach (char c in ussd.ToCharArray())
{
if (c == '#')
{
uri += Android.Net.Uri.Encode("#");
}
else
{
uri += c;
}
}
return Android.Net.Uri.Parse(uri);
}
public void StartTransaction()
{
var intent = new Intent(Intent.ActionCall, createUriFromString("*270#"));
Context ctx = Xamarin.Forms.Forms.Context;
ctx.StartActivity(intent);
}
}
}
You'll also have to register you interface, I'm using prism :
public void RegisterTypes(IContainerRegistry containerRegistry)
{
containerRegistry.Register< IUssdRenderer, UssdRenderer>();
}
The last bit is to make sure you have Call permissions enabled :
Right click on Android Project > Options > Android application
make sure CallPhone is selected

You may use Xamarin.Essentials PhoneDialer, to make a call, note that since USSD contains '#' you need to URL-encode it. example:
string code = "*123#";
PhoneDialer.Open(HttpUtility.UrlEncode(code));

After collecting from left and right I finally found the solution to my question with CrossMessaging plugin.
The steps are as follow:
Create your project and give the name
Install from nuget Xam.Plugins.Messaging in your project
Add below line in Android project MainActivity's OnCreate method:
CrossMessaging.Current.Settings().Phone.AutoDial = true;
Add android.permission.CALL_PHONE to the manifest file.
Make calls as follow
try
{
var phonedialer = CrossMessaging.Current.PhoneDialer;
if (phonedialer.CanMakePhoneCall)
{
//Ussd call's
phonedialer.MakePhoneCall(HttpUtility.UrlEncode("#150#"));
//For normal calls
phonedialer.MakePhoneCall("9111111111")
}
}
catch (Exception exc)
{
await DisplayAlert("Error!!!!", exc.ToString(), "ok");
}

The name 'CrossMedia' does not exist in the current context C# error

I am writing code for a media plug-in in Xamarin Studio, and apparently I have the following error when I try to build the app:
"The name 'CrossMedia' does not exist in the current context"
I have been trying to find a fix for the problem. Below, is the code.
using System;
using Relate.Model;
using Xamarin.Forms;
using System.IO;
namespace Relate.Views
{
public partial class EditMemberPage : ContentPage
{
public EditMemberPage()
{
InitializeComponent();
}
async void TakeaPhoto_OnClicked(object sender, EventArgs e)
{
if (CrossMedia.Current.IsCameraAvailable && CrossMedia.Current.IsTakePhotoSupported)
{
// Supply media options for saving our photo after it's taken.
var mediaOptions = new Plugin.Media.Abstractions.StoreCameraMediaOptions
{
Directory = "Receipts",
Name = $"{DateTime.UtcNow}.jpg"
};
// Take a photo of the business receipt.
var file = await CrossMedia.Current.TakePhotoAsync(mediaOptions);
}
if (CrossMedia.Current.IsCameraAvailable && CrossMedia.Current.IsTakeVideoSupported)
{
// Supply media options for saving our video after it's taken.
var mediaOptions = new Plugin.Media.Abstractions.StoreCameraMediaOptions
{
Directory = "Videos",
Name = $"{DateTime.UtcNow}.mp4"
};
// Record a video
var file = await CrossMedia.Current.TakeVideoAsync(mediaOptions);
}
// Select a photo.
if (CrossMedia.Current.IsPickPhotoSupported)
{
var photo = await CrossMedia.Current.PickPhotoAsync();
}
// Select a video.
if (CrossMedia.Current.IsPickVideoSupported)
{
var video = await CrossMedia.Current.PickVideoAsync();
}
}
async void SaveButton_OnClicked(object sender, EventArgs e)
{
var famMemberItem = (FamMember)BindingContext;
await App.Database.SaveFamMemberAsync(famMemberItem);
await Navigation.PopAsync();
}
}
}

Add using Plugin.Media; to the start of your file

Try initialize the plugin first before using it as said in its documentation.
await CrossMedia.Current.Initialize();

I know this is an old question now but I had the same problem having installed the package using the NuGet Package Manager CLI in VS2017 with:
Install-Package Xam.Plugin.Media
It seemed as though installation was not an issue but I was wrong. What I didn't realise is that it only installed it for the Android project and not for all projects. To do this you have to right click on the Solution at the top and select Manage NuGet Packages for Solution. Click on the Xam.Plugin.Media package and in an adjacent pane it will tell you whether you have it installed for all the projects in the solution with check boxes. If you have any gaps, you can then check the boxes and hit Install to complete the setup. This is mine after I corrected the issue:

Compile a Visual Studio C# project for two TargetPlatformVersion

I developed a .NET windows application which worked both on Windows 7 and 8.1. Then I added the Toast notification feature that came with Windows 8 (from this question: How can I use the Windows.UI namespace from a regular (Non-Store) Win32 .NET application?).
This also worked, I just had to add:
<PropertyGroup>
<TargetPlatformVersion>8.0</TargetPlatformVersion>
</PropertyGroup>
to the project file.
As I referenced the Windows.winmd file from the Windows 8.1 SDK C:\Program Files (x86)\Windows Kits\8.1\References\CommonConfiguration\Neutral\Windows.winmd, the executable does not start on Windows 7 anymore! I double-click and that's it. No errors, no messages.
As I did not find any solution online, that's where my question comes up: How do I manage to do both: Offer the toast feature to my users AND make the same .exe run on Windows 7?
Thank you in advance!
EDIT
It turns out that though TargetPlatformVersion is set to 8.0, the executable starts on Windows 7 anyway, but crashes as soon as the program tries to load the Windows 8 libraries:
An unhandled exception of type 'System.TypeLoadException' occurred in ToastTester.exe.
Additional information: Could not find Windows Runtime type 'Windows.UI.Notifications.ToastNotificationManager'.
on line Application.Run(new Form1());
In Form1.cs in line 9 I've got using Windows.UI.Notifications;
What is the best way to avoid this exception during runtime, even though it is expected that this executable will run in environments like Windows 7 where the Windows.UI.Notifications namespace is definitely not available?

I designed my own workaround for being able to support Windows 8 toasts and at the same time prevent application crashes due to missing libraries when running on Windows 7. Note: I am using the Singleton design pattern (member INSTANCE), but you can always do it otherwise.
ShellLink.cs is taken from here
Win8Toaster.cs:
using System;
using System.Collections.Generic;
using System.IO;
using System.Linq;
using System.Text;
using System.Windows.Forms;
using Windows.Data.Xml.Dom;
using Windows.UI.Notifications;
namespace ToastManager
{
class Win8Toaster
{
public const string APPUSERMODELID = "YourCompany.YourApplicationName";
public static string ShortcutLocation;
public static ToastNotifier ToastNotifier;
private static Win8Toaster _INSTANCE = null;
public static Win8Toaster INSTANCE
{
get
{
if (_INSTANCE == null)
{
_INSTANCE = new Win8Toaster();
}
return _INSTANCE;
}
}
public Win8Toaster()
{
ShortcutLocation = Path.Combine(Environment.GetFolderPath(Environment.SpecialFolder.ApplicationData) + #"\Microsoft\Windows\Start Menu\Programs\YourCompany\YourApplication.lnk");
//We need a start menu shortcut (a ShellLink object) to show toasts.
if (!File.Exists(ShortcutLocation))
{
string directory = Path.GetDirectoryName(ShortcutLocation);
if (!Directory.Exists(directory))
{
Directory.CreateDirectory(directory);
}
using (ShellLink shortcut = new ShellLink())
{
shortcut.TargetPath = System.Reflection.Assembly.GetEntryAssembly().Location;
shortcut.Arguments = "";
shortcut.AppUserModelID = APPUSERMODELID;
shortcut.Save(ShortcutLocation);
}
}
ToastNotifier = ToastNotificationManager.CreateToastNotifier(APPUSERMODELID);
}
public void ShowToast(ToastContent Content)
{
XmlDocument ToastContent = new XmlDocument();
ToastContent.LoadXml("<toast><visual><binding template=\"ToastImageAndText02\"><image id=\"1\" src=\"file:///" + Content.ImagePath + "\"/><text id=\"1\">" + Content.Text1 + "</text><text id=\"2\">" + Content.Text2 + "</text></binding></visual></toast>");
ToastNotification thisToast = new ToastNotification(ToastContent);
ToastNotifier.Show(thisToast);
}
}
}
Toaster.cs
using System;
using System.Collections.Generic;
using System.Windows.Forms;
namespace ToastManager
{
public static class Toaster
{
private static Win8Toaster ActiveToaster;
public static bool Win8ToasterAvailable = true;
public static void ShowToast(ToastContent Content)
{
if (Win8ToasterAvailable)
{
if (ActiveToaster == null)
{
if (Environment.OSVersion.Version.Major > 6 || Environment.OSVersion.Version.Major == 6 && Environment.OSVersion.Version.Minor >= 2)
{
try
{
ActiveToaster = Win8Toaster.INSTANCE;
}
catch (Exception ex)
{
Win8ToasterAvailable = false;
}
}
else
{
Win8ToasterAvailable = false;
}
}
ActiveToaster.ShowToast(Content);
}
else
{
//Use alternative notifications because Windows 8 Toasts are not available
}
}
}
//I also wrote my own toast content structure:
public class ToastContent
{
public string ImagePath, Text1, Text2;
public ToastContent(string ImagePath, string Text1, string Text2)
{
this.ImagePath = ImagePath;
this.Text1 = Text1;
this.Text2 = Text2;
}
}
}
Now that you've got the necessary classes, here is how to use it (pretty simple, huh?):
ToastManager.Toaster.ShowToast(new ToastManager.ToastContent(#"..\path\toyour\image.png", "Your Application Name", "Time: " + DateTime.Now.ToLongTimeString()));
This example shows a toast notification with the current system time or nothing if you are on Windows 7.
A design suggestion:
I used WinForms to design a notification window which looks similar to that in Windows 8 and simulates the same functions, just with my own forms. Alternatively you can also implement a tray icon and show some notification bubbles.

Xamarin/Android - Issue reading locally stored photo from camera - no read access

I'm trying to create a simple test app to take photos in Android, using Xamarin. When I get this app working (or so I hope), i'll use the code in a real app that I'm working on. I'm using the following recipe from Xamarin as my basis:
http://docs.xamarin.com/recipes/android/other_ux/camera_intent/take_a_picture_and_save_using_camera_app/
The major difference is that I need to store images locally, and not on the SD card. I'm able to successfully take a picture (with the Android simulator). I can see the file in the file structure using ADB and can successfully copy and open the file on my PC. However, I'm unsuccessfull in accessing the file in the app, probably due to user rights.
Please note that I was successfull in creating my own .txt files, and reading them back using either System.IO and Java.IO.
Please review the following code. My app crashes when using "System.IO.File.ReadAllText" and gives me "Access to the path "/data/data/CameraAppDemo.CameraAppDemo/files/photo.jpg" is denied.". And whatever I try (absolute, relative paths, uri's), objBitmap is always null.
ADB says that "photo.jpg" has -rwxrwx--- rights, and though I'm not entirely sure, I think that should be more than sufficient
On the other hand, maybe the intent still has a lock on "photo.jpg"? Or something else is going on...
And one final note, I'm using System.IO.File.ReadAllText just for testing purposes. I experimented with stream readers as well, but with the same result. Also, though I believe this step is unnecessary, I enabled "WriteExternalStore" in the Manifest
namespace CameraAppDemo
{
using System;
using System.Collections.Generic;
using Android.App;
using Android.Content;
using Android.Content.PM;
using Android.Graphics;
using Android.OS;
using Android.Provider;
using Android.Widget;
using Java.IO;
using Environment = Android.OS.Environment;
using Uri = Android.Net.Uri;
[Activity(Label = "Camera App Demo", MainLauncher = true)]
public class MainActivity : Activity
{
private File _file;
private string _basePath;
private ImageView _imageView;
protected override void OnActivityResult(int requestCode, Result resultCode, Intent data)
{
base.OnActivityResult(requestCode, resultCode, data);
var objBitmap = BitmapFactory.DecodeFile(_file.AbsolutePath) ;
Console.WriteLine ("objBitmap = null : " + (objBitmap == null).ToString ());
var strOutput = System.IO.File.ReadAllText (FileManager.BasePath + "/photo.jpg");
Console.WriteLine (strOutput);
}
protected override void OnCreate(Bundle bundle)
{
base.OnCreate(bundle);
SetContentView(Resource.Layout.Main);
FileManager.SetupFolderStructure();
if (IsThereAnAppToTakePictures())
{
Button button = FindViewById<Button>(Resource.Id.myButton);
_imageView = FindViewById<ImageView>(Resource.Id.imageView1);
button.Click += TakeAPicture;
}
}
private bool IsThereAnAppToTakePictures()
{
Intent intent = new Intent(MediaStore.ActionImageCapture);
IList<ResolveInfo> availableActivities = PackageManager.QueryIntentActivities(intent, PackageInfoFlags.MatchDefaultOnly);
return availableActivities != null && availableActivities.Count > 0;
}
private void TakeAPicture(object sender, EventArgs eventArgs)
{
System.IO.Directory.Delete (FileManager.BasePath, true);
_basePath = FileManager.BasePath;
_file = new Java.IO.File (_basePath, "photo.jpg");
Intent intent = new Intent(MediaStore.ActionImageCapture);
intent.PutExtra(MediaStore.ExtraOutput, Uri.FromFile(_file));
StartActivityForResult(intent, 0);
}
}
}
//Part of the FileManager class:
using System;
using System.IO;
using System.Runtime.Serialization.Formatters.Binary;
using Android.Graphics;
namespace CameraAppDemo
{
public class FileManager
{
public static string BasePath {
get {
var libraryPath = Environment.GetFolderPath (Environment.SpecialFolder.Personal);
if (Directory.Exists (libraryPath) == false) {
Directory.CreateDirectory (libraryPath);
}
return libraryPath;
}
}
}
}
==== Edit ====
It seems that I'm simply not able to read the file. As an ex-webdeveloper, I'm fairly new to programming for mobile, let alone the combo of C# and Java and I'm still learning a lot.
Anyway, I added the following lines:
Console.WriteLine("Setting file :" + _file.SetReadable (true));
Console.WriteLine("Can read :" + _file.CanRead());
Both cases return False. I can't read the file, and I am unable to give read access.
So, any ideas? Is this by design? Can I tell the Intent for taking images to give me read access, or is there another workaround?
If everything fails, I'm hoping to workaround the problem by saving to the SD card first and then copying the file to the local filesystem. But that's something I rather would not do; I can't guarantee that the end users have an SD card, and the pictures should not be deleted by accident.