Develop Reference

Action after ActivateItem in Caliburn.Micro

I have a question. I have button where i launch ActivateItem:
public void LoadTaskManagerPage()
{
this.ActivateItem(new TaskManagerViewModel(this.LoggedUser, this.repository));
if (this.LoggedUser.GetUserTask() != null)
{
this.IsActiveTaskButtonVisible = Visibility.Visible;
this.NotifyOfPropertyChange(() => this.IsActiveTaskButtonVisible);
}
}
Is it possible to hang an app and go to if statement only, if ActivateItem ends?
How to wait for end of ActivateItem in Caliburn.Micro?
EDIT:
Trying something like:
public void LoadTaskManagerPage()
{
var taskManagerTask = Task.Run(() => this.ActivateItem(new TaskManagerViewModel(this.LoggedUser, this.repository)));
taskManagerTask.Wait();
if (!this.LoggedUser.GetUserTask().IsTaskTakenByUser())
{
this.IsActiveTaskButtonVisible = Visibility.Visible;
this.NotifyOfPropertyChange(() => this.IsActiveTaskButtonVisible);
}
}
With Tasks, but when i click on LoadTaskManagerPage() it wont show any window, application hangs forever
EDIT2
Based on my issue on github, i upgraded Caliburn to alpha 4.0:
public void LoadTaskManagerPage()
{
this.ActivateItemAsync(new TaskManagerViewModel(this.LoggedUser, this.repository));
if (!this.LoggedUser.GetUserTask().IsTaskTakenByUser())
{
//logic
}
}
i changed ActiveItem() to ActiveItemAsync() but still, it hit if statement before active item will close. using async/await do the same
EDIT3
When i make async/await it still works the same, look at my view on the right. Its clicked, User Control not appear. In the same time (even when my User Control not show up) im hitting if statement too early. I want to hit it on User Control close.

You should await the ActivateItemAsync method. This means that your LoadTaskManagerPage() should return a Task and you should await this one as well:
public async Task LoadTaskManagerPageAsynnc()
{
await this.ActivateItemAsync(new TaskManagerViewModel(this.LoggedUser, this.repository));
if (!this.LoggedUser.GetUserTask().IsTaskTakenByUser())
{
//logic
}
}

How to show a WPF window from Class Library (dll) project?

I have recently made a Class Library (dll) for my other project to program a Bluetooth device via serial port (COM). The library is used to transfer firmware via COM port. It works fine until the requirement comes, which requires a WPF window to show the progress of programming. I have successfully created the progress bar using standard WPF app template. However, the standard WPF does not allow me to generate dll. After searching here, I found this link that teaches you how to add a WPF window to existing Class Library project. Also, someone teaches you how to show the window from here. Everything look good until I tried, there is nothing shows up when I call the method ProgrammBluetooth() from LabVIEW.
My main method, which is in a separate .cs file:
namespace BTMProg
{
public class BTMProgrammer
{
private bool _uut1Status = false;
private string _uut1Message = "";
public bool UUT1Status
{
get { return _uut1Status; }
set { _uut1Status = value; }
}
public string UUT1Message
{
get { return _uut1Message; }
set { _uut1Message = value; }
}
public void ProgramBluetooth (string ioPort, string firmwareFile)
{
List<UUT> uutList = new List<UUT>();
uutList.Add(new UUT(ioPort, "UUT1", 1));
Thread thread = new Thread(() =>
{
var wn = new MainWindow(uutList, firmwareFile);
wn.ShowDialog();
wn.Closed += (s, e) => wn.Dispatcher.InvokeShutdown();
Dispatcher.Run();
if (wn.TaskList[0].Result.ToUpper().Contains("SUCCESS"))
{
_uut1Status = true;
_uut1Message = wn.TaskList[0].Result;
}
else
{
_uut1Status = false;
_uut1Message = wn.TaskList[0].Result;
}
});
thread.SetApartmentState(ApartmentState.STA);
thread.Start();
}
}
}
My WPF code in MainWindow.xaml.cs:
ProgrammingViewModel _pvm = new ProgrammingViewModel();
private List<string> _viewModeList = new List<string>();
private List<Task<string>> _taskList = new List<Task<string>>();
public List<Task<string>> TaskList {
get => _taskList;
set => _taskList = value;
}
public MainWindow(List<UUT> uutList, string firmwareFile)
{
InitializeComponent();
foreach (var uut in uutList)
{
_viewModeList.Add(uut.UutName);
}
_pvm.AddProcessViewModels(_viewModeList);
ProgressBarView.DataContext = _pvm.ProcessModels;
StartProgramming(uutList, firmwareFile);
Application.Current.MainWindow.Close();
}
The issue before was that if I don't use dispatcher to create a new thread, an exception saying "The calling thread must be STA, because many UI components require this...." thrown. After I use the new thread, no error but the window does not show up as expected. What could be the problem? Thanks.

The ShowDialog function will stop execution of the thread until the window closes, meaning the rest of that code may not run and the dispatcher may not be started. You should try the Show method instead, which returns as soon as the window is shown.
Also, what is going on with these lines in the constructor of the window?
StartProgramming(uutList, firmwareFile);
Application.Current.MainWindow.Close();
Whatever that first line does, it needs to return and not do a bunch of work if you want the window to finish getting constructed. The second line makes no sense at all. Why are you closing the main window of the application? Did you even set and open a window associated with that property at some point?
I suspect one or more of these things is preventing the thread from ever reaching the point where it can show the window.

Find out which winforms controls are accessed from a background thread

We have built a huge winforms project, already in progress for multiple years.
Sometimes, our users get an exception which looks like this one.
The resolution of this problem seems to be:
don't acces UI components from a background thread
.
But since our project is a very big project with a lot of different threads, we don't succeed in finding all these.
Is there a way to check (with some tool or debugging option) which components are called from a background thread?
To clarify:
I created a sample winforms project with a single Form, containing two Button
public partial class Form1 : Form
{
public Form1()
{
InitializeComponent();
}
private void button1_Click(object sender, EventArgs e)
{
button1.Text = "Clicked!";
}
private void button2_Click(object sender, EventArgs e)
{
Task.Run(() =>
{
button2.BackColor = Color.Red; //this does not throw an exception
//button2.Text = "Clicked"; //this throws an exception when uncommented
});
}
}
The background color of button2 is set to red when the button is clicked. This happens in a background thread (which is considered bad behavior). However, it doesn't (immediately) throw an exception. I would like a way to detect this as 'bad behavior'. Preferably by scanning my code, but if it's only possible by debugging, (so pausing as soon as a UI component is accessed from a background thread) it's also fine.

I've got 2 recommendations to use together, the first is a Visual Studio Plugin called DebugSingleThread.
You can freeze all the threads and work on one at a time (obviously the non-main-UI threads) and see each threads access to controls. Tedious I know but not so bad with the second method.
The second method is to get the steps in order to reproduce the problem. If you know the steps to reproduce it, it will be easier to see whats causing it. To do this I made this User Action Log project on Github.
It will record every action a user makes, you can read about it here on SO: User Activity Logging, Telemetry (and Variables in Global Exception Handlers).
I'd recommend you also log the Thread ID, then when you have been able to reproduce the problem, go to the end of the log and work out the exact steps. Its not as painful as it seems and its great for getting application telemetry.
You might be able to customise this project, eg trap a DataSource_Completed event or add a dummy DataSource property that sets the real Grids DataSource property and raises an INotifyPropertyChanged event - and if its a non-main thread ID then Debugger.Break();.
My gut feeling is you're changing a control's (eg a grid) data source in a background thread (for that non-freeze feel) and thats causing a problem with synchronisation. This is what happened to the other DevExpress customer who experienced this. Its discussed here in a different thread to the one you referenced.

Is your app set to ignore cross threading intentionally?
Cross-thread operations should be blowing up all the time in winforms. It checks for them like crazy in just about every method. for a starting point check out https://referencesource.microsoft.com/#System.Windows.Forms/winforms/Managed/System/WinForms/Control.cs.
Somewhere in your app, somebody might have put this line of code:
Control.CheckForIllegalCrossThreadCalls = False;
Comment that out and run the app, then follow the exceptions.
(Usually you can fix the problem by wrapping the update in an invoke, e.g., in a worker thread if you see textbox1.text=SomeString; change it to `textbox.invoke(()=>{textbox1.text=SomeString;});.
You may also have to add checking for InvokeRequired, use BeginInvoke to avoid deadlocks, and return values from invoke, those are all separate topics.
this is assuming even a moderate refactor is out of the question which for even a medium sized enterprise app is almost always the case.
Note: it's not possible to guarantee successful discovery of this case thru static analysis (that is, without running the app). unless you can solve the halting problem ... https://cs.stackexchange.com/questions/63403/is-the-halting-problem-decidable-for-pure-programs-on-an-ideal-computer etc...

I did this to search for that specific situation but of course, need to adjust it to your needs, but the purpose of this is to give you at least a possibility.
I called this method SearchForThreads but since it's just an example, you can call it whatever you want.
The main idea here is perhaps adding this Method call to a base class and call it on the constructor, makes it somewhat more flexible.
Then use reflection to invoke this method on all classes deriving from this base, and throw an exception or something if it finds this situation in any class.
There's one pre req, that is the usage of Framework 4.5.
This version of the framework added the CompilerServices attribute that gives us details about the Method's caller.
The documentation for this is here
With it we can open up the source file and dig into it.
What i did was just search for the situation you specified in your question, using rudimentary text search.
But it can give you an insight about how to do this on your solution, since i know very little about your solution, i can only work with the code you put on your post.
public static void SearchForThreads(
[System.Runtime.CompilerServices.CallerMemberName] string memberName = "",
[System.Runtime.CompilerServices.CallerFilePath] string sourceFilePath = "",
[System.Runtime.CompilerServices.CallerLineNumber] int sourceLineNumber = 0)
{
var startKey = "this.Controls.Add(";
var endKey = ")";
List<string> components = new List<string>();
var designerPath = sourceFilePath.Replace(".cs", ".Designer.cs");
if (File.Exists(designerPath))
{
var designerText = File.ReadAllText(designerPath);
var initSearchPos = designerText.IndexOf(startKey) + startKey.Length;
do
{
var endSearchPos = designerText.IndexOf(endKey, initSearchPos);
var componentName = designerText.Substring(initSearchPos, (endSearchPos - initSearchPos));
componentName = componentName.Replace("this.", "");
if (!components.Contains(componentName))
components.Add(componentName);
} while ((initSearchPos = designerText.IndexOf(startKey, initSearchPos) + startKey.Length) > startKey.Length);
}
if (components.Any())
{
var classText = File.ReadAllText(sourceFilePath);
var ThreadPos = classText.IndexOf("Task.Run");
if (ThreadPos > -1)
{
do
{
var endThreadPos = classText.IndexOf("}", ThreadPos);
if (endThreadPos > -1)
{
foreach (var component in components)
{
var search = classText.IndexOf(component, ThreadPos);
if (search > -1 && search < endThreadPos)
{
Console.WriteLine($"Found a call to UI thread component at pos: {search}");
}
}
}
}
while ((ThreadPos = classText.IndexOf("Task.Run", ++ThreadPos)) < classText.Length && ThreadPos > 0);
}
}
}
I hope it helps you out.
You can get the Line number if you split the text so you can output it, but i didn't want to go through the trouble, since i don't know what would work for you.
string[] lines = classText.Replace("\r","").Split('\n');

Try that:
public static void Main(string[] args)
{
// Add the event handler for handling UI thread exceptions to the event.
Application.ThreadException += new ThreadExceptionEventHandler(exception handler);
// Set the unhandled exception mode to force all Windows Forms errors to go through the handler.
Application.SetUnhandledExceptionMode(UnhandledExceptionMode.CatchException);
// Add the event handler for handling non-UI thread exceptions to the event.
AppDomain.CurrentDomain.UnhandledException += // add the handler here
// Runs the application.
Application.Run(new ......);
}
Then you can log the message and the call stack and that should give you enough information to fix the issue.

I recommend you update your GUI to handle this situation automatically for your convenience. You instead use a set of inherited controls.
The general principle here is to override the property Set methods in a way to make them Thread Safe. So, in each overridden property, instead of a straight update of the base control, there's a check to see if an invoke is required (meaning we're on a separate thread the the GUI). Then, the Invoke call updates the property on the GUI thread, instead of the secondary thread.
So, if the inherited controls are used, the form code that is trying to update GUI elements from a secondary thread can be left as is.
Here is the textbox and button ones. You would add more of them as needed and add other properties as needed. Rather than putting code on individual forms.
You don't need to go into the designer, you can instead do a find/replace on the designer files only. For example, in ALL designer.cs files, you would replace System.Windows.Forms.TextBox with ThreadSafeControls.TextBoxBackgroundThread and System.Windows.Forms.Button with ThreadSafeControls.ButtonBackgroundThread.
Other controls can be created with the same principle, based on which control types & properties are being updated from the background thread.
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Windows.Forms;
namespace ThreadSafeControls
{
class TextBoxBackgroundThread : System.Windows.Forms.TextBox
{
public override string Text
{
get
{
return base.Text;
}
set
{
if (this.InvokeRequired)
this.Invoke((MethodInvoker)delegate { base.Text = value; });
else
base.Text = value;
}
}
public override System.Drawing.Color ForeColor
{
get
{
return base.ForeColor;
}
set
{
if (this.InvokeRequired)
this.Invoke((MethodInvoker)delegate { base.ForeColor = value; });
else
base.ForeColor = value;
}
}
public override System.Drawing.Color BackColor
{
get
{
return base.BackColor;
}
set
{
if (this.InvokeRequired)
this.Invoke((MethodInvoker)delegate { base.BackColor = value; });
else
base.BackColor = value;
}
}
}
class ButtonBackgroundThread : System.Windows.Forms.Button
{
public override string Text
{
get
{
return base.Text;
}
set
{
if (this.InvokeRequired)
this.Invoke((MethodInvoker)delegate { base.Text = value; });
else
base.Text = value;
}
}
public override System.Drawing.Color ForeColor
{
get
{
return base.ForeColor;
}
set
{
if (this.InvokeRequired)
this.Invoke((MethodInvoker)delegate { base.ForeColor = value; });
else
base.ForeColor = value;
}
}
public override System.Drawing.Color BackColor
{
get
{
return base.BackColor;
}
set
{
if (this.InvokeRequired)
this.Invoke((MethodInvoker)delegate { base.BackColor = value; });
else
base.BackColor = value;
}
}
}
}

How to add background task to Windows Store App

using c#, VS 2013
Try to add some background task to my Store app (idea to show toast if some data in my Json file contains current date and time).
What was done:
1.Create Windows Runtime Component, that implement IBackgroundTask , add reference to my Windows Store App. Inside WRC create class that contains next code :
namespace BackgroundTask
{
public sealed class EventChecker: IBackgroundTask
{
ThreadPoolTimer _periodicTimer = null;
public void Run(IBackgroundTaskInstance taskInstance)
{
_periodicTimer
= ThreadPoolTimer.CreatePeriodicTimer(new TimerElapsedHandler(PeriodicTimerCallback), TimeSpan.FromSeconds(30));
}
private void PeriodicTimerCallback(ThreadPoolTimer timer)
{
CheckEventAndShowToast();
}
....
}
2.Register task : In MainPage.xaml.cs add in method OnNavigatedTo registering of this background task. Code:
protected override void OnNavigatedTo(NavigationEventArgs e)
{
navigationHelper.OnNavigatedTo(e);
var taskName = "EventCheckerTask";
if (BackgroundTaskRegistration.AllTasks.Count > 0)
{
foreach (var cur in BackgroundTaskRegistration.AllTasks)
{
if (cur.Value.Name != taskName)
{
BackgroundTaskBuilder builder = new BackgroundTaskBuilder();
builder.Name = taskName;
builder.TaskEntryPoint = "BackgroundTask.EventChecker";
BackgroundTaskRegistration taskToRegister = builder.Register();
}
}
}
else
{
BackgroundTaskBuilder builder = new BackgroundTaskBuilder();
builder.Name = taskName;
builder.TaskEntryPoint = "BackgroundTask.EventChecker";
BackgroundTaskRegistration taskToRegister = builder.Register();
}
}
Use MSDN1, MSDN2, MSDN3 links.
Also OnComplete not implement - because i don't need it (or I must to implement it anyway?)
3.Declare in manifest.
Set toast capable to "YES":
Declare background Task:
4.Check functionality of all method that i want to use for background - all Ok and work
Durring debugging all it's ok, no errors/ exceptions, but nothing happend. Try to debug step by step - looks like all it's ok, think i make some mistake in code.
So question: where i'm wrong, why i cant launch my background task that must to check data and do required action if some conditions are as required?
EDIT
Part 2 - Try to realize background task in new solution.
What was done:
Create new simple CRC :
namespace Tasks
{
public sealed class Tasks : IBackgroundTask
{
public void Run(IBackgroundTaskInstance taskInstance)
{
//for checking place debug point
//TODO something
}
}
}
Also in main.xaml.cs placed next code:
protected override void OnNavigatedTo(NavigationEventArgs e)
{
CheckTaskRegistration();
}
private void CheckTaskRegistration()
{
foreach (var task in BackgroundTaskRegistration.AllTasks)
{
if (task.Value.Name == "Tasks")
{
isTaskRegistered = true;
break;
}
}
if (!isTaskRegistered)
{
RegisterBackgroundTask2("Tasks", "Tasks.Tasks");
}
}
private void RegisterBackgroundTask2(string name, string entrypoint)
{
BackgroundTaskBuilder btb = new BackgroundTaskBuilder();
btb.Name = name;
btb.TaskEntryPoint = entrypoint;
//IBackgroundTrigger everyMinuteTrigger = new TimeTrigger(1, false);
// btb.SetTrigger(everyMinuteTrigger);
btb.SetTrigger(new SystemTrigger(SystemTriggerType.InternetAvailable, false));
BackgroundTaskRegistration task = btb.Register();
}
As result got, that with this trigger btb.SetTrigger(new SystemTrigger(SystemTriggerType.InternetAvailable, false)); all works - i can go inside Run method, but if I try to use TimeTrigger like
//IBackgroundTrigger everyMinuteTrigger = new TimeTrigger(1, false);
// btb.SetTrigger(everyMinuteTrigger);
nothing happend - wait few minutes try few times (placed instead prev trigger registration).
Question - Why? Do i must to do something more?
Also old questions are without answers too...
Also try to use it with my App - all worksperfect, but only if i connect to lan... But why it's not work with time trigger?

A spend a little bit more time and found few root causes for my problem:
I must to use some trigger with my BackgroundTask if I want to use it and launch. problem here that ther is not exactly what i need exist (or maybe i need to read a little bit more about triggers).
So if I add some trigger, BackgroundTask can be launched after such event happend. Example:
//Time trigger
IBackgroundTrigger everyMinuteTrigger = new TimeTrigger(15, false);
btb.SetTrigger(everyMinuteTrigger);
//one of the standart tirgger
btb.SetTrigger(new SystemTrigger(SystemTriggerType.InternetAvailable, false));
If I want to use TimeTrigger, in EDIT i write code with TimeTrigger(1, false);, but after reading some more detailed documentation found "that the time trigger only accepts values greater than or equal to 15; smaller values fail during Register." MSDN
Also if I want to use TimeTrigger i must to add LockScreenNotification support to my App
Currently I can launch backgroundTask every 15 min, but it's not exactly what i want...
So, regarding this post quation - i found answer, but still need to read more deeply about BackgroundTask

Is your CheckEventAndShowToast(); calling anything asynchronously?
If that is the case then you should follow step 4 from the MSDN2 link you posted.
"4. If you run any asynchronous code in your background task, then your background task needs to use a deferral. If you don't use a deferral, then the background task process can terminate unexpectedly if the Run method completes before your asynchronous method call has completed."

SCVMM 2012 console addin execution

I'm developing an SCVMM 2012 console Add-In.
The SDK documentation can be found here: http://msdn.microsoft.com/en-us/library/jj860311.aspx
But the documentation has no info on threading or how the add-in gets executed at all.
Now here's what I have:
public class SomeAddIn : ViewAddInBase
{
private bool gotServerInfo = false;
private bool gotConnectionString = false;
public override FrameworkElement CreateViewControl()
{
GetServerInfo();
GetConnectionString();
if(gotServerInfo && gotConnectionString)
{
return GetGoodFrameworkElement(); //do some stuff to fill FrameworkElement
}
MessageBox.Show("Can't connect to DB, returning empty screen...");
return new FrameworkElement();
}
private void GetServerInfo()
{
PowerShellContext.ExecuteScript<ServerConnection>("Get-SCVMMServer localhost",
(items, error) =>
{
// code to set server info here
if (error == null)
{
gotServerInfo = true;
MessageBox.Show("Got settings from server.");
}
else{//Error}
});
}
private void GetConnectionString()
{
//PowerShell connect to database, get connection string
gotConnectionString = true; //if got string
}
}
Looks all good, but the problem is that powershell commands take time to execute and the "return new FrameworkElement();" gets executed first before gotServerInfo and gotConnectionString get set to true.
My guess is that VMM starts multiple threads for my methods and the execution of those is not sequential anymore. How do I get VMM to execute my methods in the right order?
What I've tried to do:
1) use threads for my methods, set priority to high, set current
thread priority to low or even as background, yet this doesn't help.
Thread.Join doesn't work either.
2) move my methods to "public override void OnLoad() or
OnShow(). The CreateViewControl() gets executed first anyway.
Any ideas?

Not a solution to the problem occurring during initialization, but I moved on to MVVM (WPF) and a separate threading model. After you get the basic interface up, it's up to you what you want to do and how to synchronize everything. VMM latter acts as a usual WPF application giving you one main thread for the interface. Use ThreadPool class for dispatching background tasks - found it's the easiest way to do it.