Develop Reference

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.

ManagementObjectSearcher causes re-entrancy issues for onclick handler

I am having an odd problem with protecting a section of code. My application is a tray app. I create a NotifyIcon inside my class (ApplicationContext). I have assigned a balloon click handler and a double click handler to the NotifyIcon object. there is also a context menu but I am not showing all code. Only important pieces.
public class SysTrayApplicationContext: ApplicationContext
{
private NotifyIcon notifyIcon;
private MainForm afDashBoardForm;
public SysTrayApplicationContext()
{
this.notifyIcon = new NotifyIcon();
this.notifyIcon.BalloonTipClicked += notifyIcon_BalloonTipClicked;
this.notifyIcon.MouseDoubleClick += notifyIcon_MouseDoubleClick;
// ... more code
}
Both handlers launch or create/show my form:
private void notifyIcon_MouseDoubleClick(object sender, MouseEventArgs e)
{
if (e.Button == MouseButtons.Left)
{
openDashboard();
}
}
private void notifyIcon_BalloonTipClicked(object sender, EventArgs e)
{
openDashboard();
}
private void openDashboard()
{
if (dashBoardForm != null)
{
log.Debug("Dashboard form created already, so Activate it");
dashBoardForm.Activate();
}
else
{
log.Debug("Dashboard form does not exist, create it");
dashBoardForm = new MainForm();
dashBoardForm.Show();
}
}
There is a problem with the above code. Maybe more than 1. Issue: it is possible to display 2 dashboard forms which is not what I want. If user double clicks on tray icon while balloon message is displaying causes a race condition in openDashboard. I can reproduce this easily. So I added a lock around the code in openDashboard code and, to my surprise, that did NOT prevent 2 dashboard forms from displaying. I should not be able to create 2 MainForms. Where am I going wrong here?
here is the updated code with lock statement:
private void openDashboard()
{
lock (dashBoardFormlocker)
{
if (dashBoardForm != null)
{
log.Debug("Dashboard form created already, so Activate it");
dashBoardForm.Activate();
}
else
{
log.Debug("Dashboard form does not exist, create it");
dashBoardForm = new MainForm();
dashBoardForm.Show();
}
}
}
Note: lock object was added to the class and initialized in constructor.
private object dashBoardFormlocker;
UPDATE: Showing more code. this is how code gets started :
static void Main()
{
if (SingleInstance.Start())
{
Application.EnableVisualStyles();
Application.SetCompatibleTextRenderingDefault(false);
XmlConfigurator.Configure();
// For a system tray application we don't want to create
// a form, we instead create a new ApplicationContext. The Run method takes
Application.Run(new SysTrayApplicationContext());
SingleInstance.Stop();
SingleInstance.Dispose();
}
}
}
UPDATE 2: Provide more code for clarity
public partial class MainForm : Form
{
public MainForm()
{
log.Trace("MainForm constructor...");
InitializeComponent();
// ... code not shown
this.label_OSVersion.Text = getOSFriendlyName();
// .. more code
}
private string getOSFriendlyName()
{
try
{
string result = string.Empty;
var mgmtObj = (from x in new ManagementObjectSearcher("SELECT Caption FROM Win32_OperatingSystem").Get().OfType<ManagementObject>()
select x.GetPropertyValue("Caption")).FirstOrDefault();
result = mgmtObj != null ? mgmtObj.ToString() : string.Empty;
OperatingSystem os = Environment.OSVersion;
String sp = os.ServicePack ?? string.Empty;
return !string.IsNullOrWhiteSpace(result) ? result + sp : "Unknown";
}
catch (System.Exception ex)
{
log.Error("Error trying to get the OS version", ex);
return "Unknown";
}
}
}

The main UI thread must always pump a message loop to support communication from COM components.
So when you do a blocking operation from the UI thread like locking or joining a thread, (EDIT: edited based on Peter Duniho's fix) the UI thread will enter an 'alertable' state, allowing COM to dispatch certain type of messages, which in turn can cause re-entrancy issues like in your scenario.
Look at the answer to this question (Why did entering a lock on a UI thread trigger an OnPaint event?) for a much more accurate explanation.
Looking at the source code of ManagementObjectSearcher.Get there is a lock (inside Initialize), and since you call it from the constructor of your form, it may lead to the second event triggering while the form's constructor has not finished. The assignment to the dashBoardFormlocker variable only happens after the constructor finishes, so that would explain why it was null on the second entry.
The moral of the story is never do blocking operations on the UI thread.

Without a good, minimal, complete code example that reliably reproduces the problem, it's impossible to know for sure what the problem is. But the guess by answerer tzachs seems reasonable. If so, you can fix your problem by changing your method to look like this:
private bool _dashboardOpen;
private void openDashboard()
{
if (_dashboardOpen)
{
if (dashBoardForm != null)
{
log.Debug("Dashboard form created already, so Activate it");
dashBoardForm.Activate();
}
}
else
{
log.Debug("Dashboard form does not exist, create it");
_dashboardOpen = true;
dashBoardForm = new MainForm();
dashBoardForm.Show();
}
}
In that way, any re-entrant attempt to open the window will be detected. Note that you still need the check for null before actually activating; you can't activate a window that hasn't actually finished being created yet. The subsequent call to Show() will take care of activation anyway, so ignoring the activation in the re-entrant case shouldn't matter.

Visual Studio during Debugging: The function evaluation requires all threads to run

I'm suddenly getting a strange error while debugging. Up to now the variable in the watch windows has been showing correctly. Now I am always getting this error message in the watch windows:
The function evaluation requires all threads to run
I am not able to check any variable anymore. I am not explicitly working with threads. What can I do to get it working again?
I already disabled, as mentioned in some forums, the function: "Enable property Evaluation and other implicit function Calls" in the option window of the debugger. But without success, and it gives me this error:
Error Implicit Function evaluation disabled by the user

From the msdn forum:
This isn't an error in and of itself, but more of a feature of your debugger.
Some properties require code to be executed in order for the property to be read, but if this requires cross-thread interaction, then other threads may have to run as well. The debugger doesn't do this automatically, but certainly can, with your permission.
Just click the little evaluate icon and it will run your code and evaluate the property.
For further details on this behaviour check this excelent article

I ran into this issue when just trying to get items from a table called "AGENCY" using Entity Framework:
var agencies = db.AGENCY.OrderBy(e => e.FULLNAME);
Hovering over agencies in debug mode, clicking to expand the options, and clicking Results would give the dreaded "The function evaluation requires all threads to run" with a "Do Not Enter" icon at the end that, on which, clicking did nothing.
2 possible solutions:
Add .ToList() at the end:
var agencies = db.AGENCY_TABLE.OrderBy(e => e.FULLNAME).ToList();
List<AGENCY_TABLE> agencies = db.AGENCY_TABLE.OrderBy(e => e.FULLNAME).ToList();
Credit goes to Hp93 for helping me come to this solution. In the comments on MUG4N's answer where I found this solution, it also mentions trying .Any() instead of .ToList(), but this gives a Boolean instead of a <T>, like <AGENCY> is, so it probably wouldn't help.
Workaround - try a different path in the debug options. I found that I could click on the "Non-Public Members" > "_internalQuery" > ObjectQuery > Results View and get my values that way.

MUG4N has indeed provided a correct answer however if you hover over the line of code in debug, you may be looking at something like the below. If so, click the little re-evaluate icon highlighted in the image below...
NB: I obtained this image by pinning, normally the re-evaluate icone are in the middle of the window and not down the left hand column.

You should make thread safe call because accessing Windows form controls are not Thread safe in multithreading.
This is my simple code which makes Thread safe call and sets Progress bar.
public partial class Form1 : Form
{// This delegate enables asynchronous calls for setting
// the text property on a TextBox control.
delegate void StringArgReturningVoidDelegate(string text);
private Thread demoThread = null;
public int Progresscount = 0;
static EventWaitHandle waithandler = new AutoResetEvent(false);
public Form1()
{
InitializeComponent();
}
public static bool CheckForInternetConnection()
{
try
{
using (var client = new WebClient())
{
using (var stream = client.OpenRead("http://www.google.com"))
{
return true;
}
}
}
catch
{
return false;
}
}
public void Progressincrement()
{
waithandler.WaitOne();
while (CheckForInternetConnection()==true)
{
if (Progresscount==100)
{
break;
}
SetLabel("Connected");
Progresscount += 1;
SetProgress(Progresscount.ToString());
Thread.Sleep(TimeSpan.FromSeconds(1));
}
if (Progresscount <100)
{
Startthread();
}
SetLabel("Completed");
}
public void Startthread ()
{
this.demoThread= new Thread(new ThreadStart(Progressincrement));
this.demoThread.Start();
SetLabel("Waiting for connection");
while (CheckForInternetConnection() == false) ;
waithandler.Set();
}
private void SetLabel(string text)
{
// InvokeRequired required compares the thread ID of the
// calling thread to the thread ID of the creating thread.
// If these threads are different, it returns true.
if (this.label1.InvokeRequired)
{
StringArgReturningVoidDelegate d = new StringArgReturningVoidDelegate(SetLabel);
this.Invoke(d, new object[] { text });
}
else
{
this.label1.Text = text;
}
}
private void SetProgress(string Value)
{
// InvokeRequired required compares the thread ID of the
// calling thread to the thread ID of the creating thread.
// If these threads are different, it returns true.
if (this.progressBar1.InvokeRequired)
{
StringArgReturningVoidDelegate d = new StringArgReturningVoidDelegate(SetProgress);
this.Invoke(d, new object[] {Value});
}
else
{
this.progressBar1.Value = Convert.ToInt32(Value);
}
}
private void Form1_Load(object sender, EventArgs e)
{
Startthread();
}
private void button1_Click(object sender, EventArgs e)
{
MessageBox.Show("Responsive");
}
}
For more information MSDN

This isn't an error, but more of a feature of your debugger.
The debugger doesn't do this automatically, but certainly can, with users permission. Just click the little space icon and it will run the code and evaluate the property.

I use the next workaround to pass:
var OtherThreadField = "";
Invoke(new MethodInvoker(delegate
{
OtherThreadField = ExecuteNeededMEthod();
}));
Now i have a value for OtherThreadField.

I faced the same issue and solved .The Issue arise due to username and password ,in SQL connection there is user and password but in code there no user and password. so I enable the user and the password and the issue solved

For me, this happened when trying to break on a line that accesses a complex object instance contained by a Settings Class.
A breakpoint on the following if results in Settings.Default.FindSettings with the value being "The function evaluation requires all threads to run." If I press the force eval button, it is null. Stepping with the force eval button click or not enters the if block and initializes the object. If I remove the breakpoint and add a new breakpoint following the if block, the Settings.Default.FindSettings deserializes properly with the expected values.
if (Settings.Default.FindSettings == null)
{
Settings.Default.FindSettings = new FindSettings();
}
After trial and error, I added the following code before the above if block to access the settings prior to breaking. This seems to reliably fix the problem. I do not need it in production so I wrap in conditional compiler directive. I have a comment in the code instead of a non-descript discard:
#if DEBUG
var _ = Settings.Default.FindSettings;
#endif
I am not sure if the above line would be optimized out in production since it has side effects. As I only need it while debugging, I have not checked.

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.

A Possible Threading/COM/UI problem

I am writing a toolbar for IE(6+). I have used the various sample bars from
codeproject.com (http://www.codeproject.com/KB/dotnet/IE_toolbar.aspx), and have a toolbar that works, registers unregisters etc. What I want the toolbar to do is to highlight divs within an html page as the users' mouse moves over that div. So far the highlighting code works, but I would like to display the name of the div (if it exists) in a label on the toolbar (changing as the mouse moves etc).
I cannot for the life of me get this to happen and trying to debug it is a nightmare. As the assembly is hosted in IE, I suspect that I am causing an exception (in IE) by trying to update the text on the label from a thread that didn't create that control, but because that exception is happening in IE, I don't see it.
Is the solution to try to update the control in a thread-safe way using Invoke? If so how?
Here is the event code:
private void Explorer_MouseOverEvent(mshtml.IHTMLEventObj e)
{
mshtml.IHTMLDocument2 doc = this.Explorer.Document as IHTMLDocument2;
element = doc.elementFromPoint(e.clientX, e.clientY);
if (element.tagName.Equals("DIV", StringComparison.InvariantCultureIgnoreCase))
{
element.style.border = "thin solid blue;";
if (element.className != null)
{
UpdateToolstrip(element.className);
}
}
e.returnValue = false;
}
and here is an attempt at thread-safe update of the toolbar:
delegate void UpdateToolstripDelegate(string text);
public void UpdateToolstrip(string text)
{
if (this.toolStripLabel1.InvokeRequired == false)
{
this.toolStripLabel1.Text = text;
}
else
{
this.Invoke(new UpdateToolstripDelegate(UpdateToolstrip), new object[] { text });
}
}
Any suggestions much appreciated.

I can't really reproduce the issue (creating a test project for an IE toolbar is a tad too much work), but you can try this:
Add the following routine to a public static (extensions methods) class:
public static void Invoke(this Control control, MethodInvoker methodInvoker)
{
if (control.InvokeRequired)
control.Invoke(methodInvoker);
else
methodInvoker();
}
And then replace the section of similar code in the first block with this:
if (element.className != null)
{
this.Invoke(() => toolStripLabel1.Text = element.className);
}
This is a sure-fire way of avoiding thread-safe issues in UI applications.