Getting Context.User.Identity.Name Null After Event Got Fire of SqlDependency

Getting Context.User.Identity.Name Null After Event Got Fire of SqlDependency - c#

I have first time implemented signalR concept and its working when page load first time and when I perform any insert, delete or updated operation on the database it calls a method which is specified in code but I am getting the null value of Context.User.Identity.Name. I have used FormAuthentication and after logged in I am getting connectionId and username but after make changes on a table of database getting the null value of username. Below I have mentioned my code.
HubClass
namespace SCPLTabAssessPortal
{
public class User
{
public string Name { get; set; }
public HashSet<string> ConnectionIds { get; set; }
}
[Authorize]
public class DashboardNewHub : Hub
{
int totalNewMessages = 0;
int ttltdy = 0;
int Ttlnum = 0;
int totalNewNotification = 0;
private static readonly ConcurrentDictionary<string, User> Users = new ConcurrentDictionary<string, User>();
public override Task OnConnected()
{
string userName = Context.User.Identity.Name;
string connectionId = Context.ConnectionId;
var user = Users.GetOrAdd(userName, _ => new User
{
Name = userName,
ConnectionIds = new HashSet<string>()
});
lock (user.ConnectionIds)
{
user.ConnectionIds.Add(connectionId);
Clients.AllExcept(user.ConnectionIds.ToArray()).userConnected(userName);
// TODO: Broadcast the connected user
}
return base.OnConnected();
}
public override Task OnDisconnected(bool stopCalled)
{
string name = Context.User.Identity.Name;
User rmuser;
Users.TryRemove(name, out rmuser);
return base.OnDisconnected(stopCalled);
}
public override Task OnReconnected()
{
string name = Context.User.Identity.Name;
string connectionId = Context.ConnectionId;
var user = Users.GetOrAdd(name, _ => new User
{
Name = name,
ConnectionIds = new HashSet<string>()
});
lock (user.ConnectionIds)
{
user.ConnectionIds.Add(connectionId);
Clients.AllExcept(user.ConnectionIds.ToArray()).userConnected(name);
// TODO: Broadcast the connected user
}
return base.OnReconnected();
}
[HubMethodName("sendNotifications")]
public string SendNotifications()
{
IEnumerable<string> allReceivers = null;
try
{
User getuser = GetUser(Context.User.Identity.Name);
using (var connection = new SqlConnection(ConfigurationManager.ConnectionStrings["SCPLDBPortalConnectionString"].ConnectionString))
{
string query = "SELECT [ColumnName],[ColumnName] FROM [dbo].[TableName] ";
connection.Open();
using (SqlCommand command = new SqlCommand(query, connection))
{
try
{
command.Notification = null;
DataTable dt = new DataTable();
SqlDependency dependency = new SqlDependency(command);
dependency.OnChange += new OnChangeEventHandler(dependency_OnChange);
if (connection.State == ConnectionState.Closed)
connection.Open();
var reader = command.ExecuteReader();
dt.Load(reader);
if (dt.Rows.Count > 0)
{
int totaltax = 0;
foreach (DataRow r in dt.Rows)
{
totaltax += (string.IsNullOrEmpty(Convert.ToString(r["TaxTotal"])) ? 0 : Convert.ToInt32(r["TaxTotal"]));
}
totalNewMessages = totaltax;
}
connection.Close();
}
catch (Exception ex)
{
throw;
}
}
}
User receiver;
if (Users.TryGetValue(getuser.Name, out receiver))
{
User sender = GetUser(Context.User.Identity.Name);
lock (receiver.ConnectionIds)
{
lock (sender.ConnectionIds)
{
allReceivers = receiver.ConnectionIds.Concat(sender.ConnectionIds);
}
}
foreach (var cid in allReceivers)
{
Clients.Client(cid).received(totalNewMessages);
}
}
}
catch (Exception ex) {
}
IHubContext context = GlobalHost.ConnectionManager.GetHubContext<DashboardNewHub>();
return (string)context.Clients.Client(Convert.ToString(allReceivers.Last())).RecieveNotification(totalNewMessages).Result;
}
private void dependency_OnChange(object sender, SqlNotificationEventArgs e)
{
if (e.Type == SqlNotificationType.Change)
{
DashboardNewHub nHub = new DashboardNewHub();
nHub.SendNotifications();
}
}
private User GetUser(string username)
{
User user;
Users.TryGetValue(username, out user);
return user;
}
}
}
JqueryCode
jQuery(document).ready(function () {
// Declare a proxy to reference the hub.
var notifications = $.connection.dashboardNewHub;
// Create a function that the hub can call to broadcast messages.
notifications.client.recieveNotification = function (totalNewMessages, ttltdy) {
$('#TtlColl').text(totalNewMessages);
};
// Start the connection.
$.connection.hub.start().done(function () {
notifications.server.sendNotifications();
}).fail(function (e) {
alert(e);
});
});
Global.asax.cs
protected void Application_Start(object sender, EventArgs e)
{
SqlDependency.Start(ConfigurationManager.ConnectionStrings["ConnectionString"].ConnectionString);
}
protected void Application_End(object sender, EventArgs e)
{
SqlDependency.Stop(ConfigurationManager.ConnectionStrings["ConnectionString"].ConnectionString);
}
Login.cs
The below code I wrote while a user is logging in.
FormsAuthentication.RedirectFromLoginPage(txtUserName.Text, true);
FormsAuthentication.SetAuthCookie(txtUserName.Text + "$" + DS.Tables[0].Rows[i]["ID"].ToString(), true);

The point is because is the sql broker engine to call nHub.SendNotifications() you can't get any informations about the user logged-in as is not the user logged is making the request

Related

Signal R connection state is 0 after sometime

I am using #aspnet/signalr to connect to a hub and from the hub i am calling the method to return me some data.
When i first initialize the server the connection is established normally, but if i refresh the window 3 or 4 times the client stop sending connection request to the server.
I tried logging the HubConnection, the connectionState at first is equal to 1 but after the problem accrues the connectionState is alwase equal 0
Here is how i am building the hubConnection:
buildConnection() {
this.hubConnection = new HubConnectionBuilder()
.withUrl(this.tradesService.getStockQuotationsHubUrl())
.build();
this.hubConnection.serverTimeoutInMilliseconds = 1000 * 10;
this.hubConnection.onclose(() => setTimeout(() => this.startSignalRConnection(), 2000));}
Here is how i am starting the hubConnection:
startConnection() {
this.hubConnection
.start()
.then(() => {
this.hubConnection.on('updateMethod', (data: any) => {
this.store.push([
{ type: 'update', key: data.stockID, data },
]);
});
this.dataSource = new DataSource({
store: this.store,
reshapeOnPush: true,
});
});}
Note: I am listing to 5 hubs at once in my page but the only one having problems is this one.
[Update]
The problem is from the server because when i restart the server the connection is reestablished between the client and the server, but if the client refresh or quit the page for multiple times the hub does not even try to connect to the client
public class StockQuotationsHub : Microsoft.AspNetCore.SignalR.Hub
{
private string SectorID { get; set; }
private int TradingSession { get; set; }
private int MarketID { get; set; }
public static StockQuotationExt stockQuotationExt { get; set; }
private readonly StockQuotationTicker _stockTicker;
public StockQuotationsHub(StockQuotationTicker stockTicker){
_stockTicker = stockTicker;
}
public override Task OnConnectedAsync(){
return base.OnConnectedAsync();
}
public IEnumerable<StockQuotation> GetAllStockQuotations(string[] stockID, string sectorID, int tradingSession, int marketType){
return _stockTicker.
GetAllStocks(Context.ConnectionId, stockID, sectorID, tradingSession, marketType);
}
public override async Task OnDisconnectedAsync(Exception exception){
await base.OnDisconnectedAsync(exception);
}
and here is my stock ticker class:
public IEnumerable<StockQuotation> GetAllStocks(string connectionId, string[] stockID, string sectorID, int tradingSession, int marketType)
{
_stocks = new List<StockQuotation>();
_stocks = Task.Run(async () => await GetStockQuotationModelAsync("", 0, 1, 0)).Result.ToList();
this.MaxTimeStamp = _stocks.Max(s => s.TStamp);
this.SectorID = sectorID;
this.TradingSession = tradingSession;
this.MarketID = marketType;
AddToGroups(connectionId, stockID);
if (_timer==null)
_timer = new Timer(UpdateStockPrices, null, _updateInterval, _updateInterval);
if (stockID.Length == 0)
{
return _stocks;
}
else
{
var stocksList = new List<StockQuotation>();
foreach (var stock in stockID)
{
stocksList.AddRange(_stocks.Where(s => s.StockID == stock).ToList());
}
return stocksList;
}
}
private void AddToGroups(string connectionId, string[] stockID)
{
if (_stocks.Count > 0)
{
if (stockID.Length == 0)
{
Hub.Groups.AddToGroupAsync(connectionId, "ALL");
}
else
{
foreach (var stock in stockID)
{
Hub.Groups.AddToGroupAsync(connectionId, stock);
var s = _stocks.FirstOrDefault(s => s.StockID == stock);
if(s != null)
{
s.Snapshots = new List<double>(GetStockQuotationSnapshots(stock));
}
}
}
}
}
private void AddToGroups(string connectionId, string[] stockID)
{
if (_stocks.Count > 0)
{
if (stockID.Length == 0)
{
Hub.Groups.AddToGroupAsync(connectionId, "ALL");
}
else
{
foreach (var stock in stockID)
{
Hub.Groups.AddToGroupAsync(connectionId, stock);
var s = _stocks.FirstOrDefault(s => s.StockID == stock);
if(s != null)
{
s.Snapshots = new List<double>(GetStockQuotationSnapshots(stock));
}
}
}
}
}
I really appreciated the help.

Eventually the problem was that the project type was MVC, so I changed it to be webApi
and everything worked successfully

Even if you fix it I would like to recommend you to add the following code in order to know exactly the root cause of disconnection.
First of all enable the extended debug info in the service configuration:
services.AddSignalR(o =>
{
o.EnableDetailedErrors = true;
});
Furthermore, you need to attach to the event Closed in HubConnection like that:
hubConnection.Closed += (exception) =>
{
if (exception == null)
{
Console.WriteLine("Connection closed without error.");
}
else
{
Console.WriteLine($"Connection closed due to an error: {exception}");
}
return null;
};

WebView How to run even when app is in background/closed (foreground service active)

I'm building an app which will scrape some data from a website and shows a notification when some criteria are met.
Everything works well without problems when the app is open (because the WebView is being rendered) but when I close the app the WebView is disabled so I cannot use it to scrape data anymore.
The scraping code is inside a class called from a ForegroundService.
I've already looked on the internet but I'm unable to find a solution or a substitute to WebView, do you have any ideas?
I'm sorry if this question looks stupid to you, I've started to develop for mobile just one week ago
Below the JDMonitoring class which is called from the AlarmTask class
using System;
using System.Collections.Generic;
using System.Net;
using System.Threading.Tasks;
using Xamarin.Forms;
namespace CGSJDSportsNotification {
public class JDMonitoring {
class Ticket {
string owner;
string title;
string store;
string lastUpdated;
string link;
public string ID { get; set; }
public string Owner {
get {
return owner == null ? "Nobody" : owner;
} set {
owner = value.Remove(0, value.IndexOf('(') + 1).Replace(")", "");
}
}
public string Title {
get {
return title;
} set {
if (value.StartsWith("(P"))
title = value.Remove(0, value.IndexOf(')') + 2);
}
}
public string Status { get; set; }
public string Store {
get {
return store;
} set {
store = value.Replace(#"\u003C", "").Replace(">", "");
}
}
public string LastUpdated {
get {
return lastUpdated;
} set {
string v;
int time = Convert.ToInt32(System.Text.RegularExpressions.Regex.Replace(value, #"[^\d]+", ""));
// Convert to minutes
if (value.Contains("hours"))
time *= 60;
v = time.ToString();
if (value.Contains("seconds"))
v = v.Insert(v.Length, " sec. ago");
else
v = v.Insert(v.Length, " min. ago");
lastUpdated = v;
}
}
public string Link {
get {
return link;
} set {
link = "https://support.jdplc.com/" + value;
}
}
}
public JDMonitoring() {
WB.Source = JDQueueMainUrl;
WB.Navigated += new EventHandler<WebNavigatedEventArgs>(OnNavigate);
}
IForegroundService FgService { get { return DependencyService.Get<IForegroundService>(); } }
WebView WB { get; } = MainPage.UI.MonitoringWebView;
string JDQueueMainUrl { get; } = "https://support.jdplc.com/rt4/Search/Results.html?Format=%27%3Cb%3E%3Ca%20href%3D%22__WebPath__%2FTicket%2FDisplay.html%3Fid%3D__id__%22%3E__id__%3C%2Fa%3E%3C%2Fb%3E%2FTITLE%3A%23%27%2C%0A%27%3Cb%3E%3Ca%20href%3D%22__WebPath__%2FTicket%2FDisplay.html%3Fid%3D__id__%22%3E__Subject__%3C%2Fa%3E%3C%2Fb%3E%2FTITLE%3ASubject%27%2C%0AStatus%2C%0AQueueName%2C%0AOwner%2C%0APriority%2C%0A%27__NEWLINE__%27%2C%0A%27__NBSP__%27%2C%0A%27%3Csmall%3E__Requestors__%3C%2Fsmall%3E%27%2C%0A%27%3Csmall%3E__CreatedRelative__%3C%2Fsmall%3E%27%2C%0A%27%3Csmall%3E__ToldRelative__%3C%2Fsmall%3E%27%2C%0A%27%3Csmall%3E__LastUpdatedRelative__%3C%2Fsmall%3E%27%2C%0A%27%3Csmall%3E__TimeLeft__%3C%2Fsmall%3E%27&Order=DESC%7CASC%7CASC%7CASC&OrderBy=LastUpdated%7C%7C%7C&Query=Queue%20%3D%20%27Service%20Desk%20-%20CGS%27%20AND%20(%20%20Status%20%3D%20%27new%27%20OR%20Status%20%3D%20%27open%27%20OR%20Status%20%3D%20%27stalled%27%20OR%20Status%20%3D%20%27deferred%27%20OR%20Status%20%3D%20%27open%20-%20awaiting%20requestor%27%20OR%20Status%20%3D%20%27open%20-%20awaiting%20third%20party%27%20)&RowsPerPage=0&SavedChartSearchId=new&SavedSearchId=new";
bool MonitoringIsInProgress { get; set; } = false;
public bool IsConnectionAvailable {
get {
try {
using (new WebClient().OpenRead("http://google.com/generate_204"))
return true;
} catch {
return false;
}
}
}
async Task<bool> IsOnLoginPage() {
if (await WB.EvaluateJavaScriptAsync("document.getElementsByClassName('left')[0].innerText") != null)
return true;
return false;
}
async Task<bool> Login() {
await WB.EvaluateJavaScriptAsync($"document.getElementsByName('user')[0].value = '{UserSettings.SecureEntries.Get("rtUser")}'");
await WB.EvaluateJavaScriptAsync($"document.getElementsByName('pass')[0].value = '{UserSettings.SecureEntries.Get("rtPass")}'");
await WB.EvaluateJavaScriptAsync("document.getElementsByClassName('button')[0].click()");
await Task.Delay(1000);
// Checks for wrong credentials error
if (await WB.EvaluateJavaScriptAsync("document.getElementsByClassName('action-results')[0].innerText") == null)
return true;
return false;
}
async Task<List<Ticket>> GetTickets() {
List<Ticket> tkts = new List<Ticket>();
// Queue tkts index (multiple of 2)
int index = 2;
// Iterates all the queue
while (await WB.EvaluateJavaScriptAsync($"document.getElementsByClassName('ticket-list collection-as-table')[0].getElementsByTagName('tbody')[0].getElementsByTagName('tr')[{index}].innerText") != null) {
Ticket tkt = new Ticket();
tkt.LastUpdated = await WB.EvaluateJavaScriptAsync($"document.getElementsByClassName('ticket-list collection-as-table')[0].getElementsByTagName('tbody')[0].getElementsByTagName('tr')[{index + 1}].getElementsByTagName('td')[4].innerText");
// Gets only the tkts which are not older than the value selected by the user
if (Convert.ToInt32(System.Text.RegularExpressions.Regex.Replace(tkt.LastUpdated, #"[^\d]+", "")) > Convert.ToInt32(UserSettings.Entries.Get("searchTimeframe")))
break;
tkt.ID = await WB.EvaluateJavaScriptAsync($"document.getElementsByClassName('ticket-list collection-as-table')[0].getElementsByTagName('tbody')[0].getElementsByTagName('tr')[{index}].getElementsByTagName('td')[0].innerText");
tkt.Owner = await WB.EvaluateJavaScriptAsync($"document.getElementsByClassName('ticket-list collection-as-table')[0].getElementsByTagName('tbody')[0].getElementsByTagName('tr')[{index}].getElementsByTagName('td')[4].innerText");
tkt.Title = await WB.EvaluateJavaScriptAsync($"document.getElementsByClassName('ticket-list collection-as-table')[0].getElementsByTagName('tbody')[0].getElementsByTagName('tr')[{index}].getElementsByTagName('td')[1].innerText");
tkt.Status = await WB.EvaluateJavaScriptAsync($"document.getElementsByClassName('ticket-list collection-as-table')[0].getElementsByTagName('tbody')[0].getElementsByTagName('tr')[{index}].getElementsByTagName('td')[2].innerText");
tkt.Store = await WB.EvaluateJavaScriptAsync($"document.getElementsByClassName('ticket-list collection-as-table')[0].getElementsByTagName('tbody')[0].getElementsByTagName('tr')[{index + 1}].getElementsByTagName('td')[1].innerText");
tkt.Link = await WB.EvaluateJavaScriptAsync($"document.getElementsByClassName('ticket-list collection-as-table')[0].getElementsByTagName('tbody')[0].getElementsByTagName('tr')[{index}].getElementsByTagName('td')[1].getElementsByTagName('a')[0].getAttribute('href')");
tkts.Add(tkt);
index += 2;
}
return tkts;
}
//async Task<string> QueueGetTkt
async void OnNavigate(object sender, WebNavigatedEventArgs args) {
if (MonitoringIsInProgress)
return;
if (IsConnectionAvailable) {
if (await IsOnLoginPage()) {
if (await Login() == false) {
// If the log-in failed we can't proceed
MonitoringIsInProgress = false;
FgService.NotificationNewTicket("Log-in failed!", "Please check your credentials");
// Used to avoid an infinite loop of OnNavigate method calls
WB.Source = "about:blank";
return;
}
}
// Main core of the monitoring
List<Ticket> tkts = await GetTickets();
if (tkts.Count > 0) {
foreach(Ticket t in tkts) {
// Looks only after the tkts with the country selected by the user (and if it was selected by the user, also for the tkts without a visible country)
// Firstly we look in the title
if (t.Title.Contains(MainPage.UI.CountryPicker.SelectedItem.ToString())) {
FgService.NotificationNewTicket($"[{t.ID}] {t.LastUpdated}",
$"{t.Title}\r\n\r\n" +
$"Status: {t.Status}\r\n" +
$"Owner: {t.Owner}\r\n" +
$"Last updated: {t.LastUpdated}");
break;
}
}
}
}
MonitoringIsInProgress = false;
}
}
}
AlarmTask class
using Android.App;
using Android.Content;
using Android.Support.V4.App;
namespace CGSJDSportsNotification.Droid {
[BroadcastReceiver(Enabled = true, Exported = true, DirectBootAware = true)]
[IntentFilter(new string[] { Intent.ActionBootCompleted, Intent.ActionLockedBootCompleted, "android.intent.action.QUICKBOOT_POWERON", "com.htc.intent.action.QUICKBOOT_POWERON" }, Priority = (int)IntentFilterPriority.HighPriority)]
public class AlarmTask : BroadcastReceiver {
IAlarm _MainActivity { get { return Xamarin.Forms.DependencyService.Get<IAlarm>(); } }
public override void OnReceive(Context context, Intent intent) {
if (intent.Action != null) {
if (intent.Action.Equals(Intent.ActionBootCompleted)) {
// Starts the app after reboot
var serviceIntent = new Intent(context, typeof(MainActivity));
serviceIntent.AddFlags(ActivityFlags.NewTask);
context.StartActivity(serviceIntent);
Intent main = new Intent(Intent.ActionMain);
main.AddCategory(Intent.CategoryHome);
context.StartActivity(main);
// Does not work, app crashes on boot received
/*if (UserSettings.Entries.Exists("monitoringIsRunning")) {
if ((bool)UserSettings.Entries.Get("monitoringIsRunning"))
FgService.Start();
}*/
}
} else
// Checks for new tkts on a new thread
new JDMonitoring();
// Restarts the alarm
_MainActivity.AlarmStart();
}
// Called from JDMonitoring class
public static void NotificationNewTicket(string title, string message, bool icoUnknownCountry = false) {
new AlarmTask().NotificationShow(title, message, icoUnknownCountry);
}
void NotificationShow(string title, string message, bool icoUnknownCountry) {
int countryFlag = Resource.Drawable.newTktUnknownCountry;
if (icoUnknownCountry == false) {
switch (MainPage.UI.CountryPicker.SelectedItem.ToString()) {
case "Italy":
countryFlag = Resource.Drawable.newTktItaly;
break;
case "Spain":
countryFlag = Resource.Drawable.newTktSpain;
break;
case "Germany":
countryFlag = Resource.Drawable.newTktGermany;
break;
case "Portugal":
countryFlag = Resource.Drawable.newTktPortugal;
break;
}
}
var _intent = new Intent(Application.Context, typeof(MainActivity));
_intent.AddFlags(ActivityFlags.ClearTop);
_intent.PutExtra("jdqueue_notification", "extra");
var pendingIntent = PendingIntent.GetActivity(Application.Context, 0, _intent, PendingIntentFlags.OneShot);
NotificationCompat.Builder notificationBuilder = new NotificationCompat.Builder(Application.Context, "newTktNotification_channel")
.SetVisibility((int)NotificationVisibility.Public)
.SetPriority((int)NotificationPriority.High)
.SetDefaults((int)NotificationDefaults.Sound | (int)NotificationDefaults.Vibrate | (int)NotificationDefaults.Lights)
.SetSmallIcon(Resource.Drawable.newTktNotification)
.SetLargeIcon(Android.Graphics.BitmapFactory.DecodeResource(Application.Context.Resources, countryFlag))
.SetSubText("Click to check the queue")
.SetStyle(new NotificationCompat.BigTextStyle()
.SetBigContentTitle("New ticket available!")
.BigText(message))
.SetContentText(title)
.SetAutoCancel(true)
.SetContentIntent(pendingIntent);
NotificationManagerCompat.From(Application.Context).Notify(0, notificationBuilder.Build());
}
}
}
And the ForegroundService class which is responsible to trigger for the first time the alarm
using Android.App;
using Android.Content;
using Android.OS;
namespace CGSJDSportsNotification.Droid {
[Service]
class ForegroundService : Service {
IAlarm _MainActivity { get { return Xamarin.Forms.DependencyService.Get<IAlarm>(); } }
public override IBinder OnBind(Intent intent) { return null; }
public override StartCommandResult OnStartCommand(Intent intent, StartCommandFlags flags, int startId) {
// Starts the Foreground Service and the notification channel
StartForeground(9869, new ForegroundServiceNotification().ReturnNotif());
Android.Widget.Toast.MakeText(Application.Context, "JD Queue - Monitoring started!", Android.Widget.ToastLength.Long).Show();
_MainActivity.AlarmStart();
return StartCommandResult.Sticky;
}
public override void OnDestroy() {
Android.Widget.Toast.MakeText(Application.Context, "JD Queue - Monitoring stopped!", Android.Widget.ToastLength.Long).Show();
_MainActivity.AlarmStop();
UserSettings.Entries.AddOrEdit("monitoringIsRunning", false);
UserSettings.Entries.AddOrEdit("monitoringStopPending", false, false);
base.OnDestroy();
}
public override bool StopService(Intent name) {
return base.StopService(name);
}
}
}
Thank you!

[BETTER-FINAL-SOLUTION]
After several hours I've discovered Android WebView which does exactly what I need (I'm developing this app only for Android)
I've written this Browser helper class
class Browser {
public Android.Webkit.WebView WB;
static string JSResult;
public class CustomWebViewClient : WebViewClient {
public event EventHandler<bool> OnPageLoaded;
public override void OnPageFinished(Android.Webkit.WebView view, string url) {
OnPageLoaded?.Invoke(this, true);
}
}
public Browser(CustomWebViewClient wc, string url = "") {
WB = new Android.Webkit.WebView(Android.App.Application.Context);
WB.Settings.JavaScriptEnabled = true;
WB.SetWebViewClient(wc);
WB.LoadUrl(url);
}
public string EvalJS(string js) {
JSInterface jsi = new JSInterface();
WB.EvaluateJavascript($"javascript:(function() {{ return {js}; }})()", jsi);
return JSResult;
}
class JSInterface : Java.Lang.Object, IValueCallback {
public void OnReceiveValue(Java.Lang.Object value) {
JSResult = value.ToString();
}
}
}
[EDIT]
Improved the JS returning function with async callbacks (so the JS return value will be always delivered).
Credits to ChristineZuckerman
class Browser {
public Android.Webkit.WebView WB;
public class CustomWebViewClient : WebViewClient {
public event EventHandler<bool> OnPageLoaded;
public override void OnPageFinished(Android.Webkit.WebView view, string url) {
OnPageLoaded?.Invoke(this, true);
}
}
public Browser(CustomWebViewClient wc, string url = "") {
WB = new Android.Webkit.WebView(Android.App.Application.Context);
WB.ClearCache(true);
WB.Settings.JavaScriptEnabled = true;
WB.Settings.CacheMode = CacheModes.NoCache;
WB.Settings.DomStorageEnabled = true;
WB.Settings.SetAppCacheEnabled(false);
WB.Settings.UserAgentString = "Mozilla/5.0 (Windows; U; Windows NT 6.1; en-US) AppleWebKit/534.10 (KHTML, like Gecko) Chrome/8.0.552.224 Safari/534.10";
WB.LoadUrl(url);
WB.SetWebViewClient(wc);
}
public async Task<string> EvalJS(string js, bool returnNullObjectWhenNull = true) {
string JSResult = "";
ManualResetEvent reset = new ManualResetEvent(false);
Device.BeginInvokeOnMainThread(() => {
WB?.EvaluateJavascript($"javascript:(function() {{ return {js}; }})()", new JSInterface((r) => {
JSResult = r;
reset.Set();
}));
});
await Task.Run(() => { reset.WaitOne(); });
return JSResult == "null" ? returnNullObjectWhenNull ? null : "null" : JSResult;
}
class JSInterface : Java.Lang.Object, IValueCallback {
private Action<string> _callback;
public JSInterface(Action<string> callback) {
_callback = callback;
}
public void OnReceiveValue(Java.Lang.Object value) {
string v = value.ToString();
if (v.StartsWith('"') && v.EndsWith('"'))
v = v.Remove(0, 1).Remove(v.Length - 2, 1);
_callback?.Invoke(v);
}
}
}
Example:
Browser.CustomWebViewClient wc = new Browser.CustomWebViewClient();
wc.OnPageLoaded += BrowserOnPageLoad;
Browser browser = new Browser(wc, "https://www.google.com/");
void BrowserOnPageLoad(object sender, bool e) {
string test = browser.EvalJS("document.getElementsByClassName('Q8LRLc')[0].innerText");
// 'test' will contain the value returned from the JS script
// You can acces the real WebView object by using
// browser.WB
}
// OR WITH THE NEW RETURNING FUNCTION
async void BrowserOnPageLoad(object sender, bool e) {
string test = await browser.EvalJS("document.getElementsByClassName('Q8LRLc')[0].innerText");
// 'test' will contain the value returned from the JS script
// You can acces the real WebView object by using
// browser.WB
}
[FINAL-SOLUTION]
Finally I've found an easy and efficient alternative to WebView.
Now I'm using SimpleBroswer and works great!
[SEMI-SOLUTION]
Alright, I've written a workaround but I don't really like this idea, so please, if you know a better method let me know.
Below my workaround:
In my ForegroundServiceHelper interface I've added a method to check if the MainActivity (where the WebView it's rendered) is visible or not, if isn't visible the MainActivity will be shown and immediately will be hidden back.
And the app will be removed from the last used applications
Method inside my ForegroundServiceHelper Interface
public void InitBackgroundWebView() {
if ((bool)SharedSettings.Entries.Get("MainPage.IsVisible") == false) {
// Shows the activity
Intent serviceIntent = new Intent(context, typeof(MainActivity));
serviceIntent.AddFlags(ActivityFlags.NewTask);
context.StartActivity(serviceIntent);
// And immediately hides it back
Intent main = new Intent(Intent.ActionMain);
main.AddFlags(ActivityFlags.NewTask);
main.AddCategory(Intent.CategoryHome);
context.StartActivity(main);
// Removes from the last app used
ActivityManager am = (new ContextWrapper(Android.App.Application.Context)).GetSystemService(Context.ActivityService).JavaCast<ActivityManager>();
if (am != null) {
System.Collections.Generic.IList<ActivityManager.AppTask> tasks = am.AppTasks;
if (tasks != null && tasks.Count > 0) {
tasks[0].SetExcludeFromRecents(true);
}
}
}
}
The SharedSettings class is an helper class wrapped around the App.Current.Properties Dictionary
And in the OnAppearing and OnDisappearing callbacks I set the shared values to true/false
[EDIT]
This workaround works only if the user is on the homepage, so I need to find an another solution...

Ensuring object running a long task doesn't get re instantiated

I have a WinForms application that gets Car data from a Sqlite database file which is generated by a CSV file from a WebService, and the related Parts for each Car. When instanced, the Car class populates all properties from the database and gets a lot of data from a WebService that takes about 30 seconds to finish so I just call an async Task after populating the database properties and let it run asyncronously. After the web service returns all data and all work is done, the instance is saved in a List that works like an internal cache.
All works well until the user makes an operation on a Part which requires the property ParentCar to be returned while the WebService method is still running, causing a new Car to be instantiated and re polling the web service as many times the property is requested while the Car doesn't exist on the cache list. This stops as soon as the first instance finishes processing but all changes will be overwritten every time the next instances finish.
I'm struggling to find a way to ensure that a Car is only instanced one time without blocking the UI during the application life time, any ideas?
This is the code that I currently have:
public class Car
{
private List<Part> _parts = new List<Part>();
public string Id { get; private set; }
public int DbIndex
{
get { return DbClass.GetCarIndexById(Id); }
}
public ReadOnlyCollection<Part> Parts { get => _parts.AsReadOnly(); }
public Car(System.Data.SQLite.SQLiteDataReader sQLiteDataReader)
{
// Code to Load all properties from sQLiteDataReader
Task.Run(() => LongRuningWebServiceTask());
}
private async Task LongRuningWebServiceTask
{
// Long running code that will populate even more properties
SaveToInternalDb();
}
private void SaveToInternalDb()
{
if (DbIndex > -1)
DbClass.UpdateCarData(this);
else
DbClass.AddCar(this);
}
public void RelateParts(IEnumerable<Part> parts)
{
_parts.AddRange(parts);
}
~Car()
{
SaveToInternalDb();
}
}
public class Part
{
public string ParentCarId { get; private set; }
public Car ParentCar
{
get
{
Task getCar = DbClass.GetCarById(ParentCarId);
getCar.Wait();
return getCar.Result;
}
}
}
public static class DbClass
{
private static SQLiteConnection sqlConn;
private readonly string sqlFile = "pathToDbFile";
private static List<Car> CarCache = new List<Car>();
public static async Task<Car> GetCarById(string> carId, bool ignoreCache = false)
{
Car foundCar = null;
if (!ignoreCache)
foundCar = CarCache.Find(s => s.Id == carId);
if (foundCar == null)
{
try
{
string sql = string.Format("SELECT * FROM all_Cars WHERE Car = '{0}';", carId);
using (SQLiteCommand command = new SQLiteCommand(sql, sqlConn))
{
using (SQLiteDataReader reader = (SQLiteDataReader)await command.ExecuteReaderAsync())
{
while (await reader.ReadAsync())
foundCar = new Car(reader));
}
}
}
catch (Exception e)
{
string m = e.Message;
}
if (foundCar != null)
{
var partsList = await GetPartsByCarId(carId);
if (partsList.Count > 0)
Car.RelateParts(partsList);
if (!ignoreCache)
{
if (foundCar.DbIndex == -1)
CarCache.Add(foundCar);
}
}
}
return foundCar;
}
public static async Task<List<Part>> GetPartsByCarId(string carId)
{
List<Part> foundParts = new List<Part>();
int index = GeCarIndexById(carId);
Car foundCar = index > -1 ? CarCache[index] : null;
if (foundCar != null)
foundParts = await GetPartsByCarId(carId);
return foundParts;
}
public static void InitiateSqlConnection()
{
if (sqlConn == null)
{
sqlConn = new SQLiteConnection("Data Source=" + sqlFile.FullName + ";Version=3;");
try
{
sqlConn.Open();
}
catch (Exception e)
{
var m = e.Message;
}
}
else
{
if(sqlConn.State == System.Data.ConnectionState.Broken || sqlConn.State == System.Data.ConnectionState.Closed)
sqlConn.Open();
}
}
public static int GetCarIndexById(string carId)
{
int index = -1;
for(int c = 0; c < CarCache.Count;c++)
{
if(CarCache[c].Id == carId)
{
index = c;
break;
}
}
return index;
}
public static void AddCar(Car car)
{
CarCache.Add(car);
}
public static void UpdateCarData(Car car)
{
if(car != null)
{
int index = car.DbIndex;
if(index > -1)
CarCache[index] = car;
}
}
}

Consuming Datasnap server with c#

I have a Datasnap Server and i need consuming the data with a windows phone.
The TSituacaoProxy class, when i sends a parameter (Id), the return must be a JSON object.
But the error is shown:
Object reference not set to an instance of an object.
My Code:
private void clique(object sender, RoutedEventArgs e)
{
DSRESTConnection connection = new DSRESTConnection();
connection.setHost("10.0.0.10");
connection.setPort(8080);
connection.setProtocol("http");
connection.setUserName("master");
connection.setPassword("C28861C83BD5397187FD55D04C2547F9");
connection.setContext("datasnap/REST");
DSProxy.TSituacaoProxy Proxy = new DSProxy.TSituacaoProxy(connection, ExceptionCallback);
TJSONObject jObject = TJSONObject.Parse("22");
Proxy.Loader(jObject, (TJSONObject Result) =>
{
MessageBox.Show(Result.ToString());
}, ExceptionCallback);
}
public void ExceptionCallback(Exception e)
{
MessageBox.Show(e.Message);
}
TSituacaoProxy class:
public class TSituacaoProxy : DSAdmin
{
public TSituacaoProxy(DSRESTConnection Connection, ExceptionCallback ExCal)
: base(Connection, ExCal)
{
}
private DSRESTParameterMetaData[] TSituacaoProxy_teste_Metadata;
private DSRESTParameterMetaData[] get_TSituacaoProxy_teste_Metadata()
{
if (TSituacaoProxy_teste_Metadata == null)
{
TSituacaoProxy_teste_Metadata = new DSRESTParameterMetaData[]
{
new DSRESTParameterMetaData("xValue", DSRESTParamDirection.Input, DBXDataTypes.WideStringType, "string"),
new DSRESTParameterMetaData("", DSRESTParamDirection.ReturnValue, DBXDataTypes.WideStringType, "string"),
};
}
return TSituacaoProxy_teste_Metadata;
}
The Loader method:
public delegate void LoaderCallback(TJSONObject Result);
public void Loader(TJSONObject xId, LoaderCallback callback = null, ExceptionCallback ExCal = null)
{
DSRESTCommand cmd = getConnection().CreateCommand();
cmd.setRequestType(DSHTTPRequestType.POST);
cmd.setText("TSituacaoProxy.Loader");
cmd.prepare(get_TSituacaoProxy_Loader_Metadata());
InternalConnectionDelegate LoaderDel = () =>
{
if (callback != null)
{
try
{
callback.DynamicInvoke((TJSONObject)cmd.getParameter(1).getValue().GetAsJSONValue());
}
catch (Exception ex)
{
if (ExCal != null) getConnection().syncContext.Send(new SendOrPostCallback(x => ExCal.DynamicInvoke(ex.InnerException)), null);
else getConnection().syncContext.Send(new SendOrPostCallback(x => BaseExCal.DynamicInvoke(ex.InnerException)), null);
}
}
};
cmd.getParameter(0).getValue().SetAsJSONValue(xId);
getConnection().execute(cmd, this, LoaderDel, ExCal);
}
private DSRESTParameterMetaData[] TSituacaoProxy_Select_Metadata;
private DSRESTParameterMetaData[] get_TSituacaoProxy_Select_Metadata()
{
if (TSituacaoProxy_Select_Metadata == null)
{
TSituacaoProxy_Select_Metadata = new DSRESTParameterMetaData[]
{
new DSRESTParameterMetaData("xAssorts", DSRESTParamDirection.Input, DBXDataTypes.JsonValueType, "TJSONArray"),
new DSRESTParameterMetaData("", DSRESTParamDirection.ReturnValue, DBXDataTypes.JsonValueType, "TJSONArray"),
};
}
return TSituacaoProxy_Select_Metadata;
}

change code in dsrestconnection.cs
this
HttpWebRequest Client = (HttpWebRequest)WebRequest.Create(URL + "?" + DateTime.Now.Ticks.ToString());
to this
HttpWebRequest Client =(HttpWebRequest)WebRequestCreator.ClientHttp.Create(new Uri(URL + "?" + DateTime.Now.Ticks.ToString()));

no return data from Web Method Web Service

I have a method that is a search for Branches. the parameter is Branch Code and it should return the details of the branch
public bool SearchBranch()
{
using (SqlConnection con = new SqlConnection(ConfigurationManager.ConnectionStrings["DBReader"].ConnectionString))
{
using (SqlCommand com = new SqlCommand("Reader.usp_SearchBranch", con))
{
com.CommandType = CommandType.StoredProcedure;
com.Parameters.Add("#BranchCode", SqlDbType.Int).Value = this.BranchCode;
con.Open();
SqlDataReader dr = com.ExecuteReader();
if (dr.Read())
{
this.BranchName = dr.GetValue(0).ToString();
this.AreaCode = dr.GetValue(1).ToString();
this.RegionCode = dr.GetValue(2).ToString();
this.CompanyCode = dr.GetValue(3).ToString();
this.CompanyName = dr.GetValue(4).ToString();
return true;
}
else
{
return false;
}
}
}
}
Here is my code in my Web Method in my Web Service (I dont know if this is correct)
[WebMethod(Description = "Search Affected User from Database in Access Request")]
public bool SearchBranchAccessRequest(AccessRequest accessrequest)
{
return accessrequest.SearchBranch();
}
And this is how I access/call the web method in my web page
protected void SearchBranchButton_Click(object sender, EventArgs e)
{
try
{
accessrequest.BranchCode = Convert.ToInt32(BranchCodeTextBox.Text);
iTicketWebService.SearchBranchAccessRequest(accessrequest);
if (iTicketWebService.SearchBranchAccessRequest(accessrequest) == true)
{
BranchNameLabel.Text = accessrequest.BranchName;
AreaLabel.Text = accessrequest.AreaCode;
RegionLabel.Text = accessrequest.RegionCode;
CompanyCodeLabel.Text = accessrequest.CompanyCode;
CompanyLabel.Text = accessrequest.CompanyName;
BranchEmailLabel.Text = accessrequest.BranchCode + "#pjlhuillier.com";
}
else
{
this.ClientScript.RegisterClientScriptBlock(this.GetType(), "clientScript", "<script type=\"text/javascript\">alert('Record not found. Please try again');</script>");
}
}
catch (Exception)
{
this.ClientScript.RegisterClientScriptBlock(this.GetType(), "clientScript", "<script type=\"text/javascript\">alert('Wrong Input. Please try again');</script>");
}
}
Help! it doesnt return Branch Name,Area Code,Region Code,Company Code and Company name?

change your web method as below
public AccessRequest SearchBranchAccessRequest(AccessRequest accessrequest)
{
return accessrequest.SearchBranch(accessrequest);
}
and you need to change SearchBranch() method as well
public accessrequest SearchBranch(AccessRequest accessrequest)
{
if(you found record in database)
{
// update accessrequest here
}else
{
accessrequest =null;
}
// finally return the object
return accessrequest;
}
when you call this web service
AccessRequest request = iTicketWebService.SearchBranchAccessRequest(accessrequest);
if(request!=null)
{
BranchNameLabel.Text = request.BranchName;
}
since your method signature change with above implementation, in case of null object return you can consider it as false case as your current implementation and if object return from the service you can consider it as true case.
If you need return true false from the service method and also need to have the updated object then you can have custom class to return both, like below
public class SearchBrancResponse
{
public bool SearchStatus { get; set; }
public AccessRequest AccessReq { get; set; }
}
you can then return above from the service method. from client side you have both Boolean value and the AccessRequest

Develop Reference

C# (C-Sharp) is a programming language developed by Microsoft that runs on the .NET Framework.

Getting Context.User.Identity.Name Null After Event Got Fire of SqlDependency - c#

The point is because is the sql broker engine to call nHub.SendNotifications() you can't get any informations about the user logged-in as is not the user logged is making the request

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Signal R connection state is 0 after sometime

WebView How to run even when app is in background/closed (foreground service active)

Ensuring object running a long task doesn't get re instantiated

Consuming Datasnap server with c#

no return data from Web Method Web Service

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