can anyone please help me with to parse data from xml file(bot a local file in my pc ) . I really don't know what to do ..I think i should use httpclient since it's not a local file...i know i should've put some code snippets but it's really so messed up .. as i changed in i a lot .. thanks in advance
First this the code i tried to use but it didn't work
private async void Start_Click(object sender, RoutedEventArgs e)
{
Uri resourceAddress;
// The value of 'AddressField' is set by the user and is therefore untrusted input. If we can't create a
// valid, absolute URI, we'll notify the user about the incorrect input.
if (!Helpers.TryGetUri(AddressField.Text, out resourceAddress))
{
rootPage.NotifyUser("Invalid URI.", NotifyType.ErrorMessage);
return;
}
Helpers.ScenarioStarted(StartButton, CancelButton, OutputField);
rootPage.NotifyUser("In progress", NotifyType.StatusMessage);
try
{
HttpResponseMessage response = await httpClient.GetAsync(resourceAddress).AsTask(cts.Token);
await Helpers.DisplayTextResultAsync(response, OutputField, cts.Token);
response.EnsureSuccessStatusCode();
XElement element = XElement.Parse(await response.Content.ReadAsStringAsync().AsTask(cts.Token));
OutputList.ItemsSource = (
from c in element.Elements("item")
select c.Attribute("name").Value);
rootPage.NotifyUser("Completed", NotifyType.StatusMessage);
}
catch (TaskCanceledException)
{
rootPage.NotifyUser("Request canceled.", NotifyType.ErrorMessage);
}
catch (Exception ex)
{
rootPage.NotifyUser("Error: " + ex.Message, NotifyType.ErrorMessage);
}
finally
{
Helpers.ScenarioCompleted(StartButton, CancelButton);
}
}
private void Cancel_Click(object sender, RoutedEventArgs e)
{
cts.Cancel();
cts.Dispose();
// Re-create the CancellationTokenSource.
cts = new CancellationTokenSource();
}
public void Dispose()
{
if (httpClient != null)
{
httpClient.Dispose();
httpClient = null;
}
if (cts != null)
{
cts.Dispose();
cts = null;
}
}
Related
I'm using Two await function in my program, and first one is working flawlessly but on encountering second await, my program comes out of function without executing that awaitable function and any line after that.
Not giving error and not even crashing.
Tried "wait()", "Running on main thread", "Task Run", "Threading Sleep"..
here a snippet of the code along
private async void Btn_Clicked(object sender, EventArgs e)
{
//this statement works perfectly fine
var status = await CrossPermissions.Current.RequestPermissionAsync<LocationPermission>();
//on debugging i found out it return out of function at this point without executing
var check = await CrossPermissions.Current.RequestPermissionAsync<CameraPermission>();
//None of the code is executed
Console.WriteLine("Granted");
Console.WriteLine("Granted");
}
You try to use the below method :
private async void Btn_Clicked(object sender, EventArgs e)
{
await GetPermissions();
}
public static async Task<bool> GetPermissions()
{
bool permissionsGranted = true;
var permissionsStartList = new List<Permission>()
{
Permission.Location,
Permission.Camera,
};
var permissionsNeededList = new List<Permission>();
try
{
foreach (var permission in permissionsStartList)
{
var status = await CrossPermissions.Current.CheckPermissionStatusAsync(permission);
if (status != Plugin.Permissions.Abstractions.PermissionStatus.Granted)
{
permissionsNeededList.Add(permission);
}
}
}
catch (Exception ex)
{
}
var results = await CrossPermissions.Current.RequestPermissionsAsync(permissionsNeededList.ToArray());
try
{
foreach (var permission in permissionsNeededList)
{
var status = Plugin.Permissions.Abstractions.PermissionStatus.Unknown;
//Best practice to always check that the key exists
if (results.ContainsKey(permission))
status = results[permission];
if (status == Plugin.Permissions.Abstractions.PermissionStatus.Granted || status == Plugin.Permissions.Abstractions.PermissionStatus.Unknown)
{
permissionsGranted = true;
}
else
{
permissionsGranted = false;
break;
}
}
}
catch (Exception ex)
{
}
return permissionsGranted;
}
I used WebClient to download a file in my apk. But I got this error:
Unhandled Exception:
System.Net.WebException: An exception occurred during a WebClient request.
And this is the code that I tried:
{
using (WebClient client = new WebClient())
{
client.DownloadFile(
"https://code.org/images/social-media/code-2018-creativity.png",
#"j:\storage\emulated\legacy\Download\code-2018-creativity.png");
}
}
Since you are only referring to a WebException, it may have to do with one of these cases:
The URI formed by combining BaseAddress and address is invalid.
The file or destination folder does not exist. Make sure your path to
the destination folder already exists and that you have permissions to access it.
An error occurred while
downloading data.
If you provide us more information about the exception we may be able to reduce the error to one of these cases. To get the InnerException you can do something like this:
{
using (WebClient client = new WebClient ())
{
try
{
client.DownloadFile (
"https://code.org/images/social-media/code-2018-creativity.png",
#"j:\storage\emulated\legacy\Download\code-2018-creativity.png");
}
catch (Exception ex)
{
while (ex != null)
{
Console.WriteLine (ex.Message);
ex = ex.InnerException;
}
}
}
}
You have to ask permissions on run time even you have mentioned them in your manifest file if you are running Android api level 23 or greater.
Have a look at this blog would help about how to ask a run time permission:requesting-runtime-permissions-in-android
Also, this is the official sample of how to check RuntimePermissions
Refer: xamarin-system-unauthorizedaccessexception-access-to-the-path-is-denied
Update:
To ask run time permissions, you can use this plugin:Plugin.Permissions, install it to your project.
And then, call CheckMyPermissionAsync(); before you download the file:
private void FabOnClick(object sender, EventArgs eventArgs)
{
View view = (View) sender;
CheckMyPermissionAsync();
}
In the method CheckMyPermissionAsync(), check your Storage permission and then download file:
public async void CheckMyPermissionAsync()
{
var permissionsStartList = new List<Permission>()
{
Permission.Storage
};
var permissionsNeededList = new List<Permission>();
try
{
foreach (var permission in permissionsStartList)
{
var status = await CrossPermissions.Current.CheckPermissionStatusAsync(permission);
if (status != PermissionStatus.Granted)
{
permissionsNeededList.Add(permission);
}
}
}
catch (Exception ex)
{
}
var results = await CrossPermissions.Current.RequestPermissionsAsync(permissionsNeededList.ToArray());
//Check the persimmison again
var storeagePermission = await CrossPermissions.Current.CheckPermissionStatusAsync(Permission.Storage);
if (storeagePermission == PermissionStatus.Granted)
{
//Download file here
DownloadFile("http://www.dada-data.net/uploads/image/hausmann_abcd.jpg", "XF_Downloads");
}
else {
Console.WriteLine("No permissions");
}
}
You can check the result in the completed event:
private void Completed(object sender, AsyncCompletedEventArgs e)
{
if (e.Error != null)
{
Console.WriteLine("success");
}
else
{
if (OnFileDownloaded != null) { }
Console.WriteLine("fail");
}
}
Note: pay attention to your filePath,make sure your path is correct, I use:
string pathToNewFolder = Path.Combine(Android.OS.Environment.ExternalStorageDirectory.AbsolutePath, folder);
I updated my sample here: runtime-permission-xamarin.android
I am creating a Xamarin Form PCL project for Android and IOS.
Is this possible to display multiple permission at once on the screen? My App is using Location, Storage and Camera permission. From my current code, this is displaying permission popup one by one on the different page like before use of camera i display camera permission popup. As I know three permission required for my App so i want to display a single popup for all three permission.
Below is my code for storage permission.
public static async Task<dynamic> CheckStoragePermission()
{
var result = "";
try
{
var Storagestatus = await CrossPermissions.Current.CheckPermissionStatusAsync(Plugin.Permissions.Abstractions.Permission.Storage);
if (Storagestatus != PermissionStatus.Granted)
{
await Utils.CheckPermissions(Plugin.Permissions.Abstractions.Permission.Storage);
}
}
catch (Exception ex)
{
error(ex.Message, Convert.ToString(ex.InnerException), ex.Source, ex.StackTrace);
}
return result;
}
Hope someone did this before in xamarin forms, I will thank for your help for this.
You could try using the following code to request multiple permissions at one time:
private async void Button_Clicked(object sender, EventArgs e)
{
await GetPermissions();
}
public static async Task<bool> GetPermissions()
{
bool permissionsGranted = true;
var permissionsStartList = new List<Permission>()
{
Permission.Location,
Permission.LocationAlways,
Permission.LocationWhenInUse,
Permission.Storage,
Permission.Camera
};
var permissionsNeededList = new List<Permission>();
try
{
foreach (var permission in permissionsStartList)
{
var status = await CrossPermissions.Current.CheckPermissionStatusAsync(permission);
if (status != PermissionStatus.Granted)
{
permissionsNeededList.Add(permission);
}
}
}
catch (Exception ex)
{
}
var results = await CrossPermissions.Current.RequestPermissionsAsync(permissionsNeededList.ToArray());
try
{
foreach (var permission in permissionsNeededList)
{
var status = PermissionStatus.Unknown;
//Best practice to always check that the key exists
if (results.ContainsKey(permission))
status = results[permission];
if (status == PermissionStatus.Granted || status == PermissionStatus.Unknown)
{
permissionsGranted = true;
}
else
{
permissionsGranted = false;
break;
}
}
}
catch (Exception ex)
{
}
return permissionsGranted;
}
I have two blocks of code
private async void AorBButton_Click(object sender, RoutedEventArgs e)
{
AuthenticationResult authResult = null;
ResultText.Text = string.Empty;
try
{
authResult = await App.PublicClientApp.AcquireTokenSilentAsync(scopes, App.PublicClientApp.Users.FirstOrDefault());
}
catch (MsalUiRequiredException ex)
{
// A MsalUiRequiredException happened on AcquireTokenSilentAsync. This indicates you need to call AcquireTokenAsync to acquire a token
System.Diagnostics.Debug.WriteLine($"MsalUiRequiredException: {ex.Message}");
try
{
authResult = await App.PublicClientApp.AcquireTokenAsync(scopes);
}
catch (MsalException msalex)
{
ResultText.Text = $"Error Acquiring Token:{System.Environment.NewLine}{msalex}";
}
}
catch (Exception ex)
{
ResultText.Text = $"Error Acquiring Token Silently:{System.Environment.NewLine}{ex}";
return;
}
if (authResult != null)
{
// performs one thing or the other thing
}
}
So if I click on the A button, it goes through all of the code until it gets to the final if statement and does one set of instructions.
If I press the B button, it goes through all of the same code until it gets to the final if statement but does a different set of instructions.
I think I should be able to break out the code that is exactly the same in both cases and call it from the click events and run the appropriate resultant code.
Just trying to compact the code as much as I can. I know I can do it in VBA, I just wasn't positive about how to go about it in C#.
Create another async method doing the common stuff and returning the authResult as well as a message that you can then assign to ResultText.Text. C#7's value tuples come in handy for returning the two results.
private async void AorBButton_Click(object sender, RoutedEventArgs e)
{
var (authResult, message) = await AquireToken();
ResultText.Text = message;
if (authResult != null) {
// performs one thing or the other thing
}
}
private async Task<(AuthenticationResult authResult, string message)> AquireToken()
{
AuthenticationResult authResult = null;
string message = String.Empty;
try {
authResult = await App.PublicClientApp.AcquireTokenSilentAsync(scopes, App.PublicClientApp.Users.FirstOrDefault());
} catch (MsalUiRequiredException ex) {
// A MsalUiRequiredException happened on AcquireTokenSilentAsync. This indicates you need to call AcquireTokenAsync to acquire a token
System.Diagnostics.Debug.WriteLine($"MsalUiRequiredException: {ex.Message}");
try {
authResult = await App.PublicClientApp.AcquireTokenAsync(scopes);
} catch (MsalException msalex) {
message = $"Error Acquiring Token:{System.Environment.NewLine}{msalex}";
}
} catch (Exception ex) {
message = $"Error Acquiring Token Silently:{System.Environment.NewLine}{ex}";
}
return (authResult, message);
}
It seems cleaner to me to do all the I/O stuff in the Click handlers and to execute pure logic in the AquireToken method with no dependencies on TextBoxes or Labels (ResultText). This allows you to even extract this logic to its own class.
Why does saving a file fail so often on UWP?
I open and read the contents of a specified file when the application is initially launched (with the help of a BackgroundWorker). Then when the application is suspending I try to save new content to the same file, however this results almost always in the following exception:
Unable to remove the file to be replaced. (Exception from HRESULT: 0x80070497)
My loading method:
private async static void SymbolLoader_DoWork(object sender, DoWorkEventArgs e)
{
IStorageItem file = null;
if (!UseDefault)
{
var folder = await StorageFolder.GetFolderFromPathAsync(SavePath);
file = await folder.TryGetItemAsync(FileName);
}
if (file == null)
{
file = await Package.Current.InstalledLocation.GetFileAsync(#"Assets\Default.txt");
}
var text = await FileIO.ReadTextAsync((IStorageFile)file);
Data = DoSomething(text);
}
My OnSuspending method:
private async void OnSuspending(object sender, SuspendingEventArgs e)
{
var tries = 0;
var maxTries = 10;
var deferral = e.SuspendingOperation.GetDeferral();
while (tries < maxTries)
{
var completed = await Saver.Save();
if (completed)
break;
else
{
tries++;
await Task.Delay(TimeSpan.FromSeconds(0.1));
}
}
deferral.Complete();
}
Save method:
public static async Task<bool> Save()
{
//some formatting etc.
var folder = await StorageFolder.GetFolderFromPathAsync(SavePath);
var file = await folder.CreateFileAsync(FileName, CreationCollisionOption.ReplaceExisting);
try
{
await FileIO.WriteLinesAsync(file, lines);
return true;
}
catch(Exception e)
{
return false;
}
}
It is critical that the data is saved, which is why I "solved" the problem by trying to save the file multiple times with some delay. However my solution, presented in the OnSuspending method, does not seem like the correct way to do this.
What is the correct approach? Thanks in advance!