I have a function called getMessages that can be called by a Button click (using the RelayCommand trigger) or that is called in a timer every 15s.
The desired behavior is:
webservice > deserialize answer > system notification > updatelistview > insert localDB
But when the function is called by the timer the updatelistview is not done. Why does this happen if the function is the same and works perfectly in the button command?
CODE:
// Get messages for the logged in user
public async void getMessages()
{
try
{
List<FriendGetMessage> msg = new List<FriendGetMessage>();
var response = await CommunicationWebServices.GetCHAT("users/" + au.idUser + "/get", au.token);
if (response.StatusCode == HttpStatusCode.OK) // If there are messages for me.
{
var aux = await response.Content.ReadAsStringAsync();
IEnumerable<FriendGetMessage> result = JsonConvert.DeserializeObject<IEnumerable<FriendGetMessage>>(aux);
if (result != null)
{
foreach (var m in result)
{
msg.Add(m);
}
//MsgList=msg;
foreach (var f in Friends)
{
if (f.msg == null || f.msg.Count() == 0)
{
f.msg = new ObservableCollection<Messages>();
}
foreach (var mess in msg)
{
if (mess.idUser == f.idUser)
{
Messages mm = new Messages();
mm.received = mess.message;
mm.timestamp = "Received " + mess.serverTimestamp;
mm.align = "Right";
// Add to the friend list.
f.msg.Add(mm);
// Add to Local DB
InsertMessage(null, au.idUser.ToString(), f.idUser, mess.message, mess.serverTimestamp);
var notification = new System.Windows.Forms.NotifyIcon()
{
Visible = true,
Icon = System.Drawing.SystemIcons.Information,
BalloonTipIcon = System.Windows.Forms.ToolTipIcon.Info,
BalloonTipTitle = "New Message from " + f.name,
BalloonTipText = "Message: " + mess.message,
};
// Display for 5 seconds.
notification.ShowBalloonTip(5);
// The notification should be disposed when you don't need it anymore,
// but doing so will immediately close the balloon if it's visible.
notification.Dispose();
}
}
}
counterChat = 1; // resets the counter
}
}
else {
counterChat = counterChat * 2;
}
//var sql = "select * from chat";
//var respo = GetFromDatabase(sql);
OnPropertyChanged("Friends");
}
catch (Exception e)
{
MessageBox.Show("GetMessages: " + e);
Debug.WriteLine("{0} Exception caught.", e);
}
}
CODE TIMER:
public void chatUpdate()
{
_timerChat = new DispatcherTimer(DispatcherPriority.Render);
_timerChat.Interval = TimeSpan.FromSeconds(15);
_timerChat.Tick += new EventHandler(timerchat_Tick);
_timerChat.Start();
}
public void timerchat_Tick(object sender, EventArgs e)
{
if (counterChat != incChat)
{
incChat++;
}
else
{
getMessages();
OnPropertyChanged("Friends");
incChat = 0;
}
}
ADDED - I've also tried this and didn't worked (it seems that is some kind of concurrency problem to the ObservableCollection called Friends (is a friendslist) each friend has an ObservableCollection of messages (is a chat))
public void chatUpdate()
{
_timerChat = new DispatcherTimer(DispatcherPriority.Render);
_timerChat.Interval = TimeSpan.FromSeconds(15);
_timerChat.Tick += new EventHandler(timerchat_Tick);
_timerChat.Start();
}
public async void timerchat_Tick(object sender, EventArgs e)
{
if (counterChat != incChat)
{
incChat++;
}
else
{
Application.Current.Dispatcher.Invoke((Action)async delegate { await getMessages(); });
incChat = 0;
}
}
Best regards,
I think you need to make the timer handler be an async method as follows:
public async void timerchat_Tick(object sender, EventArgs e)
{
if (counterChat != incChat)
{
incChat++;
}
else
{
await getMessages();
OnPropertyChanged("Friends");
incChat = 0;
}
}
This way OnPropertyChanged("Friends") is guaranteed to fire after the work in getMessages is done.
The methods need to change to:
DispatcherTimer _timerChat = new DispatcherTimer(DispatcherPriority.Render);
_timerChat.Interval = TimeSpan.FromSeconds(15);
_timerChat.Tick += new EventHandler(timerchat_Tick);
_timerChat.Start();
public async void timerchat_Tick(object sender, EventArgs e)
{
//...
await getMessages();
//...
}
public async Task getMessages()
{
try
{
// ... your code here
string result = await response.Content.ReadAsStringAsync();
// .... rest of your code
}
catch (Exception e)
{
MessageBox.Show("GetMessages: " + e);
}
}
It is solved. The problem was in my ViewModels I was opening multiple threads and sometimes the right one would update the UI and sometimes no.
Thanks for all the answers.
Related
I have an async function which still freezes / lags the UI thread for me when I execute it. This is my function calling it.
private void TcpListenerLogic(object sender, string e)
{
Application.Current.Dispatcher.BeginInvoke((Action)async delegate {
try
{
dynamic results = JsonConvert.DeserializeObject<dynamic>(e);
if (results.test_id != null)
{
// Get properties for new anchor
string testInformation = await CommunicationCommands.getJsonFromURL(
"http://" + ServerIP + ":" + ServerPort + "/api/" + results.test_id);
}
}
catch (Exception exception)
{
// Writing some Trace.WriteLine()'s
}
});
}
And this is the async function that freezes my UI Thread
public static async Task<string> getJsonFromURL(string url)
{
try
{
string returnString = null;
using (System.Net.WebClient client = new System.Net.WebClient())
{
returnString = await client.DownloadStringTaskAsync(url);
}
return returnString;
}
catch (Exception ex)
{
Debug.WriteLine(ex.ToString());
return null;
}
}
I already tried to make everything in TcpListenerLogic run in a new Thread:
new Thread(() =>
{
Thread.CurrentThread.IsBackground = true;
}).Start();
Which resulted in the whole UI completely freezing. And I tried to make TcpListenerLogic async and await the dispatcher, which also made everything freeze permanently. I also tried to make TcpListenerLogic async and leave the dispatcher. The dispatcher is only there because I normally have some UI code in there, which I left out for my tests.
I have ventured far through the internet, but no BackgroundWorker, ThreadPool or other methods helped me in my endeavour.
If anyone has help for this particular problem, or a resource that would improve my understanding of async functions in C#, I would much appreciate it.
Edit
As requested a deeper insight in how this event handler is called.
I have System.Net.Websocket, which is connected to the Backend API I am working with and triggers an event, everytime he receives new Data. To guarantee the socket listens as longs as it is open, there is a while loop which checks for the client state:
public event EventHandler<string> TcpReceived;
public async void StartListener(string ip, int port, string path)
{
try
{
using (client = new ClientWebSocket())
{
try
{ // Connect to backend
Uri serverUri = new Uri("ws://" + ip + ":" + port.ToString() + path );
await client.ConnectAsync(serverUri, CancellationToken.None);
}
catch (Exception ex)
{
BackendSettings.IsConnected = false;
Debug.WriteLine("Error connecting TCP Socket: " + ex.ToString());
}
state = client.State;
// Grab packages send in backend
while (client.State == WebSocketState.Open || client.State == WebSocketState.CloseSent)
{
try
{
// **Just formatting the received data until here and writing it into the "message" variable**//
TcpReceived(this, message);
// Close connection on command
if (result.MessageType == WebSocketMessageType.Close)
{
Debug.WriteLine("Closing TCP Socket.");
shouldstayclosed = true;
await client.CloseAsync(WebSocketCloseStatus.NormalClosure, string.Empty, CancellationToken.None);
break;
}
state = client.State;
}
catch
{
BackendSettings.IsConnected = false;
state = client.State;
}
}
state = client.State;
}
}
catch (Exception ex)
{
// Some error messages and settings handling
}
}
The Event has a handler attached:
TcpReceived += TcpListener_TcpReceived;
And this is the Handler, which calls the previously seen "TcpListenereLogic".
private void TcpListener_TcpReceived(object sender, string e)
{
TcpListenerLogic(sender, e);
//App.Current.Dispatcher.BeginInvoke(new Action(() => {
// TcpListenerLogic(sender, e);
//}));
//new Thread(() =>
//{
// Thread.CurrentThread.IsBackground = true;
// TcpListenerLogic(sender, e);
//}).Start();
}
I previously had the "TcpListenereLogic" as the handler, but I wanted to try different methods to call it. I also left in the commented out part, to show how the call of "TcpListenereLogic" looked already. All my attempts were with all mentioned setups and sadly lead to nothing.
Thank you very much #TheodorZoulias for helping me to find the solution to my problem.
It turns out it wasn't the async function itself, but rather how often it gets called. It got called roughly ~120 times every second.
My solution starts by calling the Listener method over a new Thread:
new Thread(() =>
{
Thread.CurrentThread.IsBackground = true;
MainWindow.tcpListener.StartListener(ip, portNumber, "/api/");
}).Start();
To limit the amount of calls that happen every second I added a dispatcher timer, that resets a bool after it has been used for a call, by my Event.
readonly System.Windows.Threading.DispatcherTimer packageIntervallTimer =
new System.Windows.Threading.DispatcherTimer();
bool readyForNewPackage = true;
private void ReadyForPackage(object sender, EventArgs e)
{
readyForNewPackage = true;
}
public async void StartListener(string ip, int port, string path)
{
packageIntervallTimer.Interval = TimeSpan.FromMilliseconds(50);
packageIntervallTimer.Tick += (s, e) => { Task.Run(() => ReadyForPackage(s, e)); };
packageIntervallTimer.Start();
Then I wrapped everything inside the while loop into an if condition based on the bool, the most important part was to have my "event EventHandler TcpReceived" in there:
// Grab packages sent in backend
while (client.State == WebSocketState.Open || client.State == WebSocketState.CloseSent)
{
if (readyForNewPackage == true)
{
readyForNewPackage = false;
try
{
....
TcpReceived(this, message);
....
}
catch
{
...
}
}
}
I added my TcpListenerLogic to the Eventhandler:
TcpReceived += TcpListenerLogic;
And my TcpListenerLogic now looked like this (names have been changed):
private async void TcpListenerLogic(object sender, string e)
{
try
{
dynamic results = JsonConvert.DeserializeObject<dynamic>(e);
if (results.test_id != null)
{
string testID = "";
if (results.test_id is JValue jValueTestId)
{
testID = jValueTestId.Value.ToString();
}
else if (results.test_id is string)
{
testID = results.test_id;
}
// Get properties for new object
string information = await CommunicationCommands.getJsonFromURL(
"http://" + ServerIP + ":" + ServerPort + "/api/" + testID );
if (information != null)
{
await App.Current.Dispatcher.BeginInvoke(new Action(() =>
{
// Create object out of the json string
TestStatus testStatus = new TestStatus();
testStatus.Deserialize(information);
if (CommunicationCommands.isNameAlreadyInCollection(testStatus.name) == false)
{
// Add new object to the list
CommunicationCommands.allFoundTests.Add(testStatus);
}
}));
{
}
catch (Exception exception)
{
....
}
}
Adding a new Thread to execute any step results in problems, so keep in mind that all this uses the thread created at the beginning for "StartListener"
I have a Form with two buttons (Start , Stop).
When I press Start Button a Task is initialized and a function is called that keeps running until Stop button is pressed.
But When I press Stop button Form freezes. why?
I have copied snippet from StackOverflow but it still freezes Form.
So tell me how to Cancel Task properly?
public partial class Form1 : Form
{
private readonly CancellationTokenSource _cts = new CancellationTokenSource();
private Task _task;
public Form1()
{
InitializeComponent();
}
//Funtion that runs when Task is initialized.
private void EventLoop(CancellationToken token)
{
//Code here..
while (!token.IsCancellationRequested)
{
//Code here..
}
if (token.IsCancellationRequested)
{
MessageBox.Show("Operation Complete..!!");
}
}
//Function for Start Button.
private void Start_Click(object sender, EventArgs e)
{
_task = Task.Factory.StartNew(() => EventLoop(_cts.Token), _cts.Token);
}
//Function for Stop button.
private void Stop_Click(object sender, EventArgs e)
{
_cts.Cancel();
}
}
Similar Example from MSDN:
var compute = Task.Factory.StartNew(() =>
{
return SumRootN(j);
}, tokenSource.Token);`
Form After Stop button is pressed.
token.IsCancellationRequested is true .
Full EventLoop() Function.
private void EventLoop(CancellationToken token)
{
SerialPort sp = new SerialPort();
string text, batch, part, courseName;
text = batch = part = courseName = "";
int courseId = 0;
this.Invoke((MethodInvoker)delegate()
{
text = portCB.SelectedItem.ToString();
batch = comboBox2.SelectedItem.ToString();
part = comboBox3.SelectedItem.ToString();
courseName = comboBox1.SelectedItem.ToString();
progressBar1.Value = 20;
using (Model1 db = new Model1())
{
courseId = db.Courses.Where(c => c.Course_name.ToUpper() == courseName.ToUpper()).Select(c => c.Course_Id).Single();
}
});
sp.PortName = text;
sp.BaudRate = 9600;
sp.Open();
while (!token.IsCancellationRequested)
{
text = sp.ReadLine();
if (text.Contains("Found ID #"))
{
this.Invoke((MethodInvoker)delegate()
{
textBox2.Clear();
textBox2.Text = "Getting Registation ID.\n";
progressBar1.Value = 60;
});
string splitText = text.Split('#')[1];
int end = splitText.IndexOf(' ');
int id = int.Parse(splitText.Substring(0, end));
using (Model1 db = new Model1())
{
var result = db.Students.Where(s => s.Reg_Id == id && s.Batch == batch && s.Class == part).Select(s => s).SingleOrDefault();
if (result != null)
{
Attendance a = new Attendance();
a.Course_Id = courseId;
a.Student_Id = id;
a.Status = "P";
a.Date = DateTime.Today.Date;
a.Batch = batch;
a.Part = part;
db.Attendances.Add(a);
string message = "";
if (db.SaveChanges() != 0)
{
message = "Attendance Uploaded..!!\n";
}
else
{
message = "Attendance Not Uploaded ..!!\n";
}
this.Invoke((MethodInvoker)delegate()
{
progressBar1.Value = 100;
textBox2.AppendText(message);
});
}
else
{
this.BeginInvoke((MethodInvoker)delegate()
{
textBox2.AppendText("Student Does not belong to Specified Batch Or Part..\n");
});
}
}
}
else
{
this.Invoke((MethodInvoker)delegate()
{
textBox2.AppendText("No Match Found..!! \n");
});
}
this.Invoke((MethodInvoker)delegate()
{
textBox1.AppendText(text + "\n");
});
}
sp.Close();
// This exception will be handled by the Task
// and will not cause the program to crash
if (token.IsCancellationRequested)
{
//MessageBox.Show("Operation Comptele..!!");
}
}
You call MessageBox.Show("Operation Complete..!!"); in the progress of cancellation. This is highly not recommended, not talking about that you are calling an UI operation from other than the UI thread.
Comment the MessageBox.Show("Operation Complete..!!"); line out
* Edit *
Question author's comment on his original question, found the mistake, which line was removed from the post. Here are my conclusion:
Always try to isolate an issue, and reproduce in its purest form. During that process you will probably diagnose and find the issues itself :-).
So if the code with issue is long to post, it is definitely not the way just deleting lines then post it. The way is deleting lines and see if the issue exist, with other words: Isolating the issue in its purest reproducable form
please use async call on your task
private async void Start_Click(object sender, EventArgs e)
{
_task = Task.Factory.StartNew(() => EventLoop(_cts.Token), _cts.Token);
await task;
}
It is my first program on wifi direct so I made a simple program that just discover all nearby devices and then try to connect to one of them the discovery works fine and gets all the devices the problem is in the connection that always fails after using this function WiFiDirectDevice.FromIdAsync() it keeps paring for too long and then it fails always.
I was following the code on this microsoft tutorial: https://channel9.msdn.com/Events/Build/2015/3-98
Here is my code:
// The Blank Page item template is documented at http://go.microsoft.com/fwlink/?LinkId=402352&clcid=0x409
namespace App7
{
public sealed partial class MainPage : Page
{
public MainPage()
{
this.InitializeComponent();
}
DeviceInformationCollection DevicesFound;
WiFiDirectAdvertisementPublisher pub;
WiFiDirectConnectionListener listener;
CancellationTokenSource m_CancellationTokenSource;
private async void button_Click(object sender, RoutedEventArgs e)
{
String DeviceSelector = WiFiDirectDevice.GetDeviceSelector(WiFiDirectDeviceSelectorType.AssociationEndpoint);
DevicesFound = await DeviceInformation.FindAllAsync(DeviceSelector);
if(DevicesFound.Count>0)
{
connectedDeviceslist.ItemsSource = DevicesFound;
var dialog = new MessageDialog(DevicesFound[0].Name);
await dialog.ShowAsync();
}
}
private async void button1_Click(object sender, RoutedEventArgs e)
{
int selectedIndex = connectedDeviceslist.SelectedIndex;
String deviceID = DevicesFound[selectedIndex].Id;
var selecetedDevice = DevicesFound[selectedIndex];
try
{
WiFiDirectConnectionParameters connectionParams = new WiFiDirectConnectionParameters();
connectionParams.GroupOwnerIntent = Convert.ToInt16("1");
connectionParams.PreferredPairingProcedure = WiFiDirectPairingProcedure.GroupOwnerNegotiation;
m_CancellationTokenSource = new CancellationTokenSource();
var wfdDevice = await WiFiDirectDevice.FromIdAsync(selecetedDevice.Id, connectionParams).AsTask(m_CancellationTokenSource.Token);
var EndpointPairs = wfdDevice.GetConnectionEndpointPairs();
}
catch(Exception ex)
{
await Dispatcher.RunAsync(CoreDispatcherPriority.High, async() =>
{
var dialog = new MessageDialog(ex.Message);
await dialog.ShowAsync();
});
}
}
private void button2_Click(object sender, RoutedEventArgs e)
{
pub = new WiFiDirectAdvertisementPublisher();
pub.Advertisement.ListenStateDiscoverability = WiFiDirectAdvertisementListenStateDiscoverability.Normal;
listener = new WiFiDirectConnectionListener();
listener.ConnectionRequested += OnConnectionRequested;
pub.Start();
}
private async void OnConnectionRequested(WiFiDirectConnectionListener sender, WiFiDirectConnectionRequestedEventArgs args)
{
try
{
var ConnectionRequest = args.GetConnectionRequest();
var tcs = new TaskCompletionSource<bool>();
var dialogTask = tcs.Task;
var messageDialog = new MessageDialog("Connection request received from " + ConnectionRequest.DeviceInformation.Name, "Connection Request");
// Add commands and set their callbacks; both buttons use the same callback function instead of inline event handlers
messageDialog.Commands.Add(new UICommand("Accept", null, 0));
messageDialog.Commands.Add(new UICommand("Decline", null, 1));
// Set the command that will be invoked by default
messageDialog.DefaultCommandIndex = 1;
// Set the command to be invoked when escape is pressed
messageDialog.CancelCommandIndex = 1;
await Dispatcher.RunAsync(CoreDispatcherPriority.High, async () =>
{
// Show the message dialog
var commandChosen = await messageDialog.ShowAsync();
tcs.SetResult((commandChosen.Label == "Accept") ? true : false);
});
var fProceed = await dialogTask;
if (fProceed == true)
{
var tcsWiFiDirectDevice = new TaskCompletionSource<WiFiDirectDevice>();
var wfdDeviceTask = tcsWiFiDirectDevice.Task;
// WriteToOutput("Connecting to " + ConnectionRequest.DeviceInformation.Name + "...");
WiFiDirectConnectionParameters ConnectionParams = new WiFiDirectConnectionParameters();
await Dispatcher.RunAsync(CoreDispatcherPriority.High, async () =>
{
try
{
ConnectionParams.GroupOwnerIntent = 14;
tcsWiFiDirectDevice.SetResult(await WiFiDirectDevice.FromIdAsync(ConnectionRequest.DeviceInformation.Id, ConnectionParams));
}
catch (Exception ex)
{
// WriteToOutput("FromIdAsync task threw an exception: " + ex.ToString());
}
});
WiFiDirectDevice wfdDevice = await wfdDeviceTask;
var EndpointPairs = wfdDevice.GetConnectionEndpointPairs();
/* m_ConnectedDevices.Add("dummy", wfdDevice);
WriteToOutput("Devices connected on L2, listening on IP Address: " + EndpointPairs[0].LocalHostName.ToString() + " Port: " + Globals.strServerPort);
StreamSocketListener listenerSocket = new StreamSocketListener();
listenerSocket.ConnectionReceived += OnSocketConnectionReceived;
await listenerSocket.BindEndpointAsync(EndpointPairs[0].LocalHostName, Globals.strServerPort);*/
}
else
{
/* // Decline the connection request
WriteToOutput("Connection request from " + ConnectionRequest.DeviceInformation.Name + " was declined");
ConnectionRequest.Dispose();*/
}
}
catch (Exception ex)
{
//WriteToOutput("FromIdAsync threw an exception: " + ex.ToString());
}
}
}
}
I got a strange issue with my searchBox in Windows 8.1 App.
I got an unhandler exception (and a crush) if in my Suggestion i do not append the querySuggestion and append only the ResultSuggestion.
the problem occurs when i change the queryText.
This is my function
public async void OnSuggest(Windows.UI.Xaml.Controls.SearchBox e, SearchBoxSuggestionsRequestedEventArgs args)
{
var deferral = args.Request.GetDeferral();
var queryText = args.QueryText != null ? args.QueryText.Trim() : null;
if (string.IsNullOrEmpty(queryText)) return;
TransporterExt tr_search = new TransporterExt();
tr_search.name = queryText;
try
{
var suggestionCollection = args.Request.SearchSuggestionCollection;
ObservableCollection<TransporterExt> querySuggestions = await TransporterService.Search(tr_search);
if (querySuggestions != null && querySuggestions.Count > 0)
{
foreach (TransporterExt tr in querySuggestions)
{
//if (tr.name.ToUpperInvariant().Contains(e.QueryText.ToUpperInvariant()))
//{
// //suggestionCollection.AppendQuerySuggestion(tr.name);
// suggestionCollection.AppendResultSuggestion(tr.name,
// tr.trId.ToString(),
// tr.trId.ToString(),
// imgRef, "imgDesc");
//}
suggestionCollection.AppendQuerySuggestion(tr.name);
}
}
}
catch (Exception)
{
//Ignore any exceptions that occur trying to find search suggestions.
}
deferral.Complete();
}
I got the searchBox inside an UserControl
My controller code
public delegate void SuggestionsRequested(Windows.UI.Xaml.Controls.SearchBox sender, SearchBoxSuggestionsRequestedEventArgs args);
public event Windows.Foundation.TypedEventHandler<Windows.UI.Xaml.Controls.SearchBox, SearchBoxSuggestionsRequestedEventArgs> SearchBoxSuggestionsRequested;
private void SearchBoxSuggestions(Windows.UI.Xaml.Controls.SearchBox sender, SearchBoxSuggestionsRequestedEventArgs args)
{
if (SearchBoxSuggestionsRequested != null)
SearchBoxSuggestionsRequested(sender, args);
}
I got this exception
WinRT: A method was called at an unexpected time.
exception: System.InvalidOperationException - type (string)
Edited Solution - Working function
First of all i remove from the constructor of the page the registration of event
public TruckCrudPage()
{
this.InitializeComponent();
this.navigationHelper = new NavigationHelper(this);
this.navigationHelper.LoadState += navigationHelper_LoadState;
this.navigationHelper.SaveState += navigationHelper_SaveState;
//this.truckForm.SearchBoxSuggestionsRequested += OnSuggest;
}
public async void OnSuggest(Windows.UI.Xaml.Controls.SearchBox e, SearchBoxSuggestionsRequestedEventArgs args)
{
var deferral = args.Request.GetDeferral();
TransporterExt tr_search = new TransporterExt();
ObservableCollection<TransporterExt> querySuggestions = new ObservableCollection<TransporterExt>();
var queryText = args.QueryText != null ? args.QueryText.Trim() : null;
if (string.IsNullOrEmpty(queryText)) return;
suggested.Clear();
tr_search.name = queryText;
try
{
var suggestionCollection = args.Request.SearchSuggestionCollection;
querySuggestions = await TransporterService.Search(tr_search);
if (querySuggestions != null && querySuggestions.Count > 0 )
{
int i = 0;
foreach (TransporterExt tr in querySuggestions)
{
if (tr.name.StartsWith(e.QueryText, StringComparison.CurrentCultureIgnoreCase))
//if (tr.name.ToLower().Contains(e.QueryText))
{
string name = tr.name;
string detail = tr.trId.ToString();
string tag = i.ToString();
string imageAlternate = "imgDesc";
suggestionCollection.AppendResultSuggestion(name, detail, tag, imgRef, imageAlternate);
suggested.Add(tr);
//Debug.WriteLine("dentro" + suggested.Count);
i++;
}
}
}
}
catch (Exception exc)
{
//Ignore any exceptions that occur trying to find search suggestions.
Debug.WriteLine("Exception generata " + exc.Message);
Debug.WriteLine(exc.StackTrace);
}
deferral.Complete();
}
But it works only with condition StartsWith and i would like to use Contains
You can use SearchBox and SuggestionRequested event to fire the event when type on the SearchBox. I will show an Example
<SearchBox x:Name="SearchBoxSuggestions" SuggestionsRequested="SearchBoxEventsSuggestionsRequested"/>
and write the SearchBoxEventsSuggestionsRequested handler in the code behind
private void SearchBoxEventsSuggestionsRequested(object sender, SearchBoxSuggestionsRequestedEventArgs e)
{
string queryText = e.QueryText;
if (!string.IsNullOrEmpty(queryText))
{
Windows.ApplicationModel.Search.SearchSuggestionCollection suggestionCollection = e.Request.SearchSuggestionCollection;
foreach (string suggestion in SuggestionList)
{
if (suggestion.StartsWith(queryText, StringComparison.CurrentCultureIgnoreCase))
{
suggestionCollection.AppendQuerySuggestion(suggestion);
}
}
}
}
You can add the keyword to SuggestioList, and it will show in the dropdown when you type on the Searchbox.
Create the SuggestionList
public List<string> SuggestionList { get; set; }
initialize the list
SuggestionList = new List<string>();
and add keywords to the list
SuggestionList.Add("suggestion1");
SuggestionList.Add("suggestion2");
SuggestionList.Add("suggestion3");
SuggestionList.Add("suggestion4");
SuggestionList.Add("Fruits");
When you type s on the Searchbox it will show all the keyword starts with s.
Thanks.
void device_DeviceArrived(ProximityDevice sender)
{
//Compatible Device enters area
if (stance == WriteStage.PREP)
{
System.Diagnostics.Debug.WriteLine("Writestages won");
//Perhaps here
updateStatusRectangle(Colors.Yellow);
stance = WriteStage.WRITING;
updateStatusText("Writing...");
writeToTag(msg);
}
else
{
updateReceivedText("Device connected!");
}
}
private void MessageReceivedHandler(ProximityDevice sender, ProximityMessage message)
{
System.Diagnostics.Debug.WriteLine("Handler ran");
var rawMsg = message.Data.ToArray();
var ndefMessage = NdefMessage.FromByteArray(rawMsg);
foreach (NdefRecord record in ndefMessage)
{
System.Diagnostics.Debug.WriteLine("Record type: " + Encoding.UTF8.GetString(record.Type, 0, record.Type.Length));
var specType = record.CheckSpecializedType(false);
if (specType == typeof(NdefTextRecord))
{
var textrec = new NdefTextRecord(record);
updateReceivedText(textrec.Text);
}
}
}
The above event and handler are executed when the phone comes into contact with an NFC device. For intents and purposes in this app, I need to ensure that before writing to a card, if it already has content, it will prompt the user to verify overwriting the data. I commented where I think it should go, but as far as checking for the Message, I'm not sure how to go about it. I can't call the handler without the ProximityMessage, and I don't know of another way to view the message.
The Question: Is it possible to call the MessageReceivedHandler (or check the message at all), from device_DeviceArrived?
(Note: Debug.Writelines are for test purposes, and this is just a quick NFC writer I'm throwing together).
UPDATE: In attempting to find a work around, I ran into a different problem.
public bool promptUserForOverwrite()
{
bool response = false;
Dispatcher.BeginInvoke(() =>
{
MessageBoxResult cc = MessageBox.Show("You are about to overwrite data. Proceed?", "Overwrite?", MessageBoxButton.OKCancel);
if (cc == MessageBoxResult.OK)
{
System.Diagnostics.Debug.WriteLine("MessageBox OK result");
response = true;
}
});
return response;
}
private void MessageReceivedHandler(ProximityDevice sender, ProximityMessage message)
{
System.Diagnostics.Debug.WriteLine("Handler ran");
var rawMsg = message.Data.ToArray();
var ndefMessage = NdefMessage.FromByteArray(rawMsg);
foreach (NdefRecord record in ndefMessage)
{
System.Diagnostics.Debug.WriteLine("Record type: " + Encoding.UTF8.GetString(record.Type, 0, record.Type.Length));
var specType = record.CheckSpecializedType(false);
if (specType == typeof(NdefTextRecord))
{
var textrec = new NdefTextRecord(record);
updateReceivedText(textrec.Text);
}
}
bool pow = promptUserForOverwrite();
if (!pow)
{
System.Diagnostics.Debug.WriteLine("Prompt returned");
//This always hits - pow is always false.
}
if (stance == WriteStage.WRITING && pow)
{
//writeToTag(msg);
}
}
This would work as a work around; the problem is the beginInvoke method. I need it for cross thread access, but used like this seems to make it run at a later time (when the thread is free?). The bool pow is always false, even after I click ok on the messagebox (debugged, and it does get the result, but after I can no longer use it). Is there an alternative that I can use for the Dispatcher?
Ugly, but I have this working. You need to get a TaskScheduler from the UI thread, so declare a
private TaskScheduler sched;
and then on the OnLoaded event for the page
sched = TaskScheduler.FromCurrentSynchronizationContext();
Then your methods
public async Task<bool> promptUserForOverwrite()
{
return false;
}
private async void MessageReceivedHandler(ProximityDevice sender, ProximityMessage message)
{
System.Diagnostics.Debug.WriteLine("Handler ran");
var rawMsg = message.Data.ToArray();
var ndefMessage = NdefMessage.FromByteArray(rawMsg);
foreach (NdefRecord record in ndefMessage)
{
System.Diagnostics.Debug.WriteLine("Record type: " + Encoding.UTF8.GetString(record.Type, 0, record.Type.Length));
var specType = record.CheckSpecializedType(false);
if (specType == typeof(NdefTextRecord))
{
var textrec = new NdefTextRecord(record);
updateReceivedText(textrec.Text);
}
}
var task = promptUserForOverwrite();
var pow = await task.ContinueWith(t =>
{
MessageBoxResult cc = MessageBox.Show("You are about to overwrite data. Proceed?", "Overwrite?", MessageBoxButton.OKCancel);
if (cc == MessageBoxResult.OK)
{
System.Diagnostics.Debug.WriteLine("MessageBox OK result");
return true;
}
else
{
return false;
}
}, CancellationToken.None, TaskContinuationOptions.OnlyOnFaulted, sched);
if (!pow)
{
System.Diagnostics.Debug.WriteLine("Prompt returned");
//This always hits - pow is always false.
}
if (stance == WriteStage.WRITING && pow)
{
//writeToTag(msg);
}
}