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  • WPF Dispatcher.UnhandledException within a ShowDialog call.

    - by Eric
    It appears that ShowDialog() invokes the Dispatcher message handling loop within. Thus, you have a stack that looks something like: Outer-most Dispatcher message loop ... x.ShowDialog() Inner Dispatcher message loop ... I am using the Dispatcher.UnhandledException to catch exceptions not handled by my code. However, it appears that the Inner Dispatcher message loop, above, is undesirably catching exceptions that my code would catch. Example: Outer-most Dispatcher message loop try/catch FooException ... x.ShowDialog() Inner Dispatcher message loop ... throw FooException What I would like is for the thrown FooException to get caught by the try/catch. However. It gets caught first by the (inner) Dispatcher.UnhandledException. I see there are ways to filter the exception. However, those filters will apply to both the inner and outer most handlers. What I am looking for is to have my Dispatcher.UnhandledException code run only on the outer-most dispatcher message loop. Does that make sense? I could, of course, reflect the call stack from within my handler to see if this is the outer-most dispatcher, but that seems a bit fragile. Other ideas? Thanks! Eric

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  • Understanding “Dispatcher” in WPF

    - by Pawan_Mishra
    Level : Beginner to intermediate Consider the following program MainWindow.xaml 1: < Window x:Class ="DispatcherTrial.MainWindow" 2: xmlns ="http://schemas.microsoft.com/winfx/2006/xaml/presentation" 3: xmlns:x ="http://schemas.microsoft.com/winfx/2006/xaml" 4: Title ="MainWindow" Height ="350" Width ="525" > 5: < Grid > 6: < Grid.RowDefinitions > 7: < RowDefinition /> 8: < RowDefinition /> 9: </ Grid.RowDefinitions...(read more)

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  • Understanding the Silverlight Dispatcher

    - by Matt
    I had a Invalid Cross Thread access issue, but a little research and I managed to fix it by using the Dispatcher. Now in my app I have objects with lazy loading. I'd make an Async call using WCF and as usual I use the Dispatcher to update my objects DataContext, however it didn't work for this scenario. I did however find a solution here. Here's what I don't understand. In my UserControl I have code to call an Toggle method on my object. The call to this method is within a Dispatcher like so. Dispatcher.BeginInvoke( () => _CurrentPin.ToggleInfoPanel() ); As I mentioned before this was not enough to satisfy Silverlight. I had to make another Dispatcher call within my object. My object is NOT a UIElement, but a simple class that handles all its own loading/saving. So the problem was fixed by calling Deployment.Current.Dispatcher.BeginInvoke( () => dataContext.Detail = detail ); within my class. Why did I have to call the Dispatcher twice to achieve this? Shouldn't a high-level call be enough? Is there a difference between the Deployment.Current.Dispatcher and the Dispatcher in a UIElement?

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  • WPF - Dispatcher PushFrame()

    - by Tri Q
    Hello, I'm trying to call Dispatcher.PushFrame() from several different thread but encounter an error: Must create DependencySource on same Thread as the DependencyObject. Here is a code snippet: _lockFrame = new DispatcherFrame(true); Dispatcher.PushFrame(_lockFrame); When I tried: Dispatcher.CurrentDispatcher.Invoke( DispatcherPriority.Normal, new Action(() => _lockFrame = new DispatcherFrame(true)); Dispatcher.PushFrame(_lockFrame); I get the error: Objects must be created by the same thread. What is the approach for pushing multiple frames into the Dispatcher from different threads?

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  • WPF: Modifying CollectionView from Dispatcher still throws errors

    - by Dusda
    I have the following bit of code that modifies an observable collection of 'screens' whenever a user leaves. void OnUserLeft(int roomId, int userId, string username) { client.ClientDispatcher.Invoke( (Action<int>)((id) => { Console.WriteLine("Hello before the storm!"); var screensToCheck = client.Screens.Where(s => s.CpuId == id).ToList(); screensToCheck.Each(s => client.Screens.Remove(s)); Console.WriteLine("Hello there!"); }), userId); } This is wrapped in a call to the client's Dispatcher, supposedly to get past the threading issues related to CollectionViews. However, I still get the following exception: This type of CollectionView does not support changes to its SourceCollection from a thread different from the Dispatcher thread. The Dispatcher you see above is set in the WPF application's MainViewModel (we're using MVVM), like so: public Dispatcher ClientDispatcher { get { return Dispatcher.CurrentDispatcher; } }

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  • How to access Dispatcher in Silverlight tests?

    - by bluebit
    I am using the SL unit test framework for tests (http://code.msdn.microsoft.com/silverlightut). My code is heavily client-server communications dependant, and I access the GUI dispatcher in several places to make sure important data is only accessed on a single thread (ie. the GUI thread). This dispatcher seems unavailable in the unit tests - I have tried using Deployment.Current.Dispatcher and even created an instance of a blank control to try use its own dispatcher, but both don't work. The code inside of Dispatcher.BeginInvoke() just never executes, even if I include a Thread.Sleep afterwards.

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  • org.apache.struts2.dispatcher.Dispatcher: Could not find action or result Error

    - by peterwkc
    i tried to code the following simple struts but encounter this error during run time. [org.apache.struts2.dispatcher.Dispatcher] Could not find action or result: No result defined for action com.peter.action.LoginAction and result success index.jsp <%@ page language="java" contentType="text/html; charset=ISO-8859-1" pageEncoding="ISO-8859-1"%> <%@ taglib prefix="s" uri="/struts-tags" %> <!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd"> <html> <head> <meta http-equiv="Content-Type" content="text/html; charset=ISO-8859-1"> <title>Struts Tutorial</title> </head> <body> <h2>Hello Struts</h2> <s:form action="login" > <s:textfield name="username" label="Username:" /> <s:password name="password" label="Password:"/> <s:submit /> </s:form> </body> </html> LoginAction.java /** * */ package com.peter.action; //import org.apache.struts2.convention.annotation.Namespace; import org.apache.struts2.convention.annotation.ResultPath; import org.apache.struts2.convention.annotation.Result; import org.apache.struts2.convention.annotation.Action; import com.opensymphony.xwork2.ActionSupport; /** * @author nicholas_tse * */ //@Namespace("/") To define URL namespace @ResultPath("/") // To instruct Struts where to search result page(jsp) public class LoginAction extends ActionSupport { private String username, password; /** * */ private static final long serialVersionUID = -8992836566328180883L; /** * */ public LoginAction() { // TODO Auto-generated constructor stub } public String getUsername() { return username; } public void setUsername(String username) { this.username = username; } public String getPassword() { return password; } public void setPassword(String password) { this.password = password; } @Override @Action(value = "login", results = {@Result(name="success", location="welcome.jsp")}) public String execute() { return SUCCESS; } } /* Remove * struts2-gxp-plugin * struts2-portlet-plugin * struts2-jsf-plugin * struts2-osgi-plugin and its related osgi-plugin * struts-rest-plugin * * Add * velocity-tools-view * * */ web.xml <?xml version="1.0" encoding="UTF-8"?> <web-app id="WebApp_ID" version="3.0" xmlns="http://java.sun.com/xml/ns/javaee" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/web-app_3_0.xsd"> <display-name>Struts</display-name> <!-- org.apache.struts2.dispatcher.ng.filter.StrutsPrepareAndExecuteFilter org.apache.struts2.dispatcher.FilterDispatcher --> <filter> <filter-name>Struts_Filter</filter-name> <filter-class>org.apache.struts2.dispatcher.FilterDispatcher</filter-class> <init-param> <param-name>actionPackages</param-name> <param-value>com.peter.action</param-value> </init-param> </filter> <filter-mapping> <filter-name>Struts_Filter</filter-name> <url-pattern>/*</url-pattern> </filter-mapping> <listener> <listener-class>org.springframework.web.context.ContextLoaderListener</listener-class> </listener> <welcome-file-list> <welcome-file>index.jsp</welcome-file> </welcome-file-list> </web-app> Besides the runtime error, there is deployment error which is ERROR [com.opensymphony.xwork2.util.finder.ClassFinder] (MSC service thread 1-2) Unable to read class [WEB-INF.classes.com.peter.action.LoginAction]: Could not load WEB-INF/classes/com/peter/action/LoginAction.class - [unknown location] at com.opensymphony.xwork2.util.finder.ClassFinder.readClassDef(ClassFinder.java:785) [xwork-core-2.3.1.2.jar:2.3.1.2] AFAIK, the scanning methodology of struts will scan the default packages named struts2 for any annotated class but i have instructed struts2 to scan in com.peter.action using init-param but still unable to find the class. It is pretty weird. Please help. Thanks.

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  • Why is Dispatcher.Invoke not triggering UI update?

    - by Brandon
    I am trying to reuse a UserControl and also borrow some logic that keeps track of progress. I'll try and simplify things. MyWindow.xaml includes a MyUserControl. MyUserControl has its own progress indicator (Formatting in progress..., Copying files..., etc.) and I'd like to mirror this progress somewhere in the MyWindow form. But, the user control has some logic I don't quite understand. I've read and read but I still don't understand the Dispatcher. Here's a summary of the logic in the user control that updates the progress. this.Dispatcher.Invoke(DispatcherPriority.Input, (Action)(() => { DAProgressIndicator = InfiniteProgress.AddNewInstanceToControl(StatusGrid, new SolidColorBrush(new Color() { A = 170, R = 128, G = 128, B = 128 }), string.Empty); DAProgressIndicator.Message = MediaCardAdminRes.ActivatingCard; ActivateInProgress = true; })); I thought I'd be smart and add an event to MyUserControl that would be called in the ActivateInProgress property set logic. public bool ActivateInProgress { get { return _activateInProgress; } set { _activateInProgress = value; if (ActivateInProgressHandler != null) { ActivateInProgressHandler(value); } } } I'm setting the ActivateInProgressHandler within the MyWindow constructor to the following method that sets the view model property that is used for the window's own progress indicator. private void SetActivation(bool activateInProgress) { viewModel.ActivationInProgress = activateInProgress; } However, the window's progress indicator never changes. So, I'm convinced that the Dispatcher.Invoke is doing something that I don't understand. If I put a message box inside the SetActivation method, the thread blocks and the window's progress indicator is updated. I understand basic threads but this whole Dispatcher thing is new to me. What am I missing?

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  • logic before dispatcher + controller?

    - by Spoonface
    I believe for a typical MVC web application the router / dispatcher routine is used to decide which controller is loaded based primarily on the area requested in the url by the user. However, in addition to checking the url query string, I also like to use the dispatcher to check whether the user is currently logged in or not to decide which controller is loaded. For example if they are logged in and request the login page, the dispatcher would load their account instead. But is this a fairly non-standard design? Would it violate MVC in any way? I only ask as the examples I've read through this weekend have had no major calculations performed before the dispatcher routine, and commonly check whether the user is logged in or not per controller, and then redirect where necessary. But to me it seems odd to redirect a logged in user from the login area to account area if you could just load the account controller in the first place? I hope I've explained my consternation well enough, but could anyone offer some details on how they handle logged in users, and similar session data?

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  • [MVC] logic before dispatcher + controller?

    - by Spoonface
    I believe for a typical MVC web application the router / dispatcher routine is used to decide which controller is loaded based primarily on the area requested in the url by the user. However, in addition to checking the url query string, I also like to use the dispatcher to check whether the user is currently logged in or not to decide which controller is loaded. For example if they are logged in and request the login page, the dispatcher would load their account instead. But is this a fairly non-standard design? Would it violate MVC in any way? I only ask as the examples I've read through this weekend have had no major calculations performed before the dispatcher routine, and commonly check whether the user is logged in or not per controller, and then redirect where necessary. But to me it seems odd to redirect a logged in user from the login area to account area if you could just load the account controller in the first place? I hope I've explained my consternation well enough, but could anyone offer some details on how they handle logged in users, and similar session data?

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  • Application.Current.Shutdown() vs. Application.Current.Dispatcher.BeginInvokeShutdown()

    - by Daniel Rose
    First a bit of background: I have a WPF application, which is a GUI-front-end to a legacy Win32-application. The legacy app runs as DLL in a separate thread. The commands the user chooses in the UI are invoked on that "legacy thread". If the "legacy thread" finishes, the GUI-front-end cannot do anything useful anymore, so I need to shutdown the WPF-application. Therefore, at the end of the thread's method, I call Application.Current.Shutdown(). Since I am not on the main thread, I need to invoke this command. However, then I noticed that the Dispatcher also has BeginInvokeShutdown() to shutdown the dispatcher. So my question is: What is the difference between invoking Application.Current.Shutdown(); and calling Application.Current.Dispatcher.BeginInvokeShutdown();

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  • Getting the right WPF dispatcher in a thread.

    - by Bert
    Hi, In the constructor of an object i need to create a WPF mediaElement object: m_videoMedia = new MediaElement(); but the class can also be instantiated from a other thread so i need to use Dispatcher.Invoke(DispatcherPriority.Normal, (Action)(() => { m_videoMedia = new MediaElement(); })); But how can I get the right dispatcher instance in that constructor :s

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  • Dispatcher.BeginInvoke problems

    - by cmaduro
    I'm getting "An object reference is required for the non-static field, method, or property 'System.Windows.Threading.Dispatcher.BeginInvoke(System.Action)'" for this code. private void ResponseCompleted(IAsyncResult result) { HttpWebRequest request = result.AsyncState as HttpWebRequest; HttpWebResponse response = request.EndGetResponse(result) as HttpWebResponse; using (StreamReader sr = new StreamReader(response.GetResponseStream())) { Dispatcher.BeginInvoke( () => { try { XDocument resultsXml = XDocument.Load(sr); QueryCompleted(new QueryCompletedEventArgs(resultsXml)); } catch (XmlException e) { XDocument errorXml = new XDocument(new XElement("error", e.Message)); QueryCompleted(new QueryCompletedEventArgs(errorXml)); } }); } } }

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  • How to invoke WPF Dispatcher in Nunit?

    - by Reporting Avatar
    I want to test an application which renders a text block with a data field value. I would like to get the actual width and actual height, once the rendering completes. Everything works fine. The problem came first, when I tried to test the application. I'm unable to invoke the dispatcher from the test project. Following is the code. this.Loaded += (s, e) => { TextBlock textBlock1 = new TextBlock(); //// Text block value is assigned from data base field. textBlock1.Text = strValueFromDataBaseField; //// Setting the wrap behavior. textBlock1.TextWrapping = TextWrapping.WrapWithOverflow; //// Adding the text block to the layout canvas. this.layoutCanvas.Children.Add(textBlock1); this.Dispatcher.BeginInvoke(DispatcherPriority.Background, (Action)(() => { //// After rendering the text block with the data base field value. Measuring the actual width and height. this.TextBlockActualWidth = textBlock1.ActualWidth; this.TextBlockActualHeight = textBlock1.ActualHeight; //// Other calculations based on the actual widht and actual height. } )); }; I've just started using the NUnit. So, please help me. Thanks

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  • Threading 101: What is a Dispatcher?

    - by Water Cooler v2
    Once upon a time, I remembered this stuff by heart. Over time, my understanding has diluted and I mean to refresh it. As I recall, any so called single threaded application has two threads: a) the primary thread that has a pointer to the main or DllMain entry points; and b) For applications that have some UI, a UI thread, a.k.a the secondary thread, on which the WndProc runs, i.e. the thread that executes the WndProc that recieves messages that Windows posts to it. In short, the thread that executes the Windows message loop. For UI apps, the primary thread is in a blocking state waiting for messages from Windows. When it recieves them, it queues them up and dispatches them to the message loop (WndProc) and the UI thread gets kick started. As per my understanding, the primary thread, which is in a blocking state, is this: C++ while(getmessage(/* args &msg, etc. */)) { translatemessage(&msg, 0, 0); dispatchmessage(&msg, 0, 0); } C# or VB.NET WinForms apps: Application.Run( new System.Windows.Forms() ); Is this what they call the Dispatcher? My questions are: a) Is my above understanding correct? b) What in the name of hell is the Dispatcher? c) Point me to a resource where I can get a better understanding of threads from a Windows/Win32 perspective and then tie it up with high level languages like C#. Petzold is sparing in his discussion on the subject in his epic work. Although I believe I have it somewhat right, a confirmation will be relieving.

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  • In NetworkManager, my nm-dispatcher is never called.

    - by Alain Pannetier
    I've got two Ubuntu laptops (both 10.10). One is a new Maverick install and the other has been upgraded many times since 9.04. On the latter, setting up a custom script hook in /etc/NetworkManager/dispatcher.d/ worked instantaneously. However, on the older laptop, I can't get nm-dispatcher to get called, or at least to execute its hooks. I've tried to run NetworkManager --no-daemon -log-level=DEBUG But there is no mention of nm-dispatcher. How can I Have a look at the source (I looked into the git repo but could not find anything. find why the nm-dispatcher never gets called.

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  • WPF Dispatcher timer tick freezes my application

    - by Nebo
    I've got a little problem using WPF Dispatcher Timer. On each timer tick my application freezes for a moment (until timer tick method finishes). This is my code: private DispatcherTimer _Timer = new DispatcherTimer(); _Timer.Tick += new EventHandler(_DoLoop); _Timer.Interval = TimeSpan.FromMilliseconds(1500); _Timer.Start(); Is there any way to avoid this and have my application run smoothly?

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  • Dispatcher Timer Problem

    - by will
    I am trying to make a game in silverlight that also has widgets in it. To do this I am using a dispatcher timer running a game loop that updates graphics etc. In this I have a variable that has to be accessed by both by the constantly running game loop and UI event code. At first look it seemed that the gameloop had its own local copy of currentUnit (the variable), despite the variable being declared globally. I am trying to update currentUnit with an event by the widget part of the app, but the timer's version of the variable is not being updated. What can I do get the currentUnit in the gameloop loop to be updated whenever I update currentUnit via a click event? Here is the code for setting currentUnit as part of a click event DataContractJsonSerializer serializer = new DataContractJsonSerializer(typeof(Unit)); currentUnit = serializer.ReadObject(e.Result) as Unit; txtName.Text = currentUnit.name; Canvas.SetLeft(txtName, 100 - (int)Math.Ceiling(txtName.ActualWidth) / 2); txtX.Text = "" + currentUnit.x; txtY.Text = "" + currentUnit.y; txtX.Text = "" + currentUnit.owner; txtY.Text = "" + currentUnit.moved; txtName.Text = "" + currentUnit.GetHashCode(); And here is a snippet from the gameLoop loop //deal with phase changes and showing stuff if (txtPhase.Text == "Move" && movementPanel.Visibility == Visibility.Collapsed) { if (currentUnit != null) { if (currentUnit.owner) { if (currentUnit.moved) { txtMoved.Text = "This Unit has Already Moved!"; movementPanel.Visibility = Visibility.Collapsed; } else { txtMoved.Text = "" + currentUnit.GetHashCode(); movementPanel.Visibility = Visibility.Visible; } } else { txtMoved.Text = "bam"; movementPanel.Visibility = Visibility.Collapsed; } } else { txtMoved.Text = "slam"; movementPanel.Visibility = Visibility.Collapsed; } //loadUnitList(); } Here is the code for my unit class. using System; public class Unit { public int id { get; set; } public string name { get; set; } public string image { get; set; } public int x { get; set; } public int y { get; set; } public bool owner { get; set; } public int rotation { get; set; } public double movement { get; set; } public string type { get; set; } public bool moved { get; set; } public bool fired { get; set; } } Overall, any simple types, like a double is being 'updated' correctly, yet a complex of my own type (Unit) seems to be holding a local copy. Please help, I've asked other places and no one has had an answer for me!

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  • How can I exclude pages created from a specific template from the CQ5 dispatcher cache?

    - by Shawn
    I have a specific Adobe CQ5 (5.5) content template that authors will use to create pages. I want to exclude any page that is created from this template from the dispatcher cache. As I understand it currently, the only way I know to prevent caching is to configure dispatcher.any to not cache a particular URL. But in this case, the URL isn't known until a web author uses the template to create a page. I don't want to have to go back and modify dispatcher.any every time a page is created--or at least I want to automate this if there is no other way. I am using IIS for the dispatcher. The reason I don't want to cache the pages is because the underlying JSPs that render the content for these pages produce dynamic content, and the pages don't use querystrings and won't carry authentication headers. The pages will be created in unpredictable directories, so I don't know the URL pattern ahead of time. How can I configure things so that any page that is created from a certain template will be automatically excluded from the dispatcher cache? It seems like CQ ought to have some mechanism to respect HTTP response/caching headers. If the HTTP response headers specify that the response shouldn't be cached, it seems like the dispatcher shouldn't cache it--regardless of what dispatcher.any says. This is the CQ5 documentation I have been referencing.

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  • Dispatcher.CurrentDispatcher?

    - by Mark
    If I do this... public PriorityQueue(Dispatcher dispatcher = null) { this.dispatcher = dispatcher ?? Dispatcher.CurrentDispatcher; } And then use it in a ViewModel (without passing any args) that is created through the XAML, this.dispatcher will point to the UI thread right?

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  • Launching a WPF Window in a Separate Thread, Part 1

    - by Reed
    Typically, I strongly recommend keeping the user interface within an application’s main thread, and using multiple threads to move the actual “work” into background threads.  However, there are rare times when creating a separate, dedicated thread for a Window can be beneficial.  This is even acknowledged in the MSDN samples, such as the Multiple Windows, Multiple Threads sample.  However, doing this correctly is difficult.  Even the referenced MSDN sample has major flaws, and will fail horribly in certain scenarios.  To ease this, I wrote a small class that alleviates some of the difficulties involved. The MSDN Multiple Windows, Multiple Threads Sample shows how to launch a new thread with a WPF Window, and will work in most cases.  The sample code (commented and slightly modified) works out to the following: // Create a thread Thread newWindowThread = new Thread(new ThreadStart( () => { // Create and show the Window Window1 tempWindow = new Window1(); tempWindow.Show(); // Start the Dispatcher Processing System.Windows.Threading.Dispatcher.Run(); })); // Set the apartment state newWindowThread.SetApartmentState(ApartmentState.STA); // Make the thread a background thread newWindowThread.IsBackground = true; // Start the thread newWindowThread.Start(); .csharpcode, .csharpcode pre { font-size: small; color: black; font-family: consolas, "Courier New", courier, monospace; background-color: #ffffff; /*white-space: pre;*/ } .csharpcode pre { margin: 0em; } .csharpcode .rem { color: #008000; } .csharpcode .kwrd { color: #0000ff; } .csharpcode .str { color: #006080; } .csharpcode .op { color: #0000c0; } .csharpcode .preproc { color: #cc6633; } .csharpcode .asp { background-color: #ffff00; } .csharpcode .html { color: #800000; } .csharpcode .attr { color: #ff0000; } .csharpcode .alt { background-color: #f4f4f4; width: 100%; margin: 0em; } .csharpcode .lnum { color: #606060; } This sample creates a thread, marks it as single threaded apartment state, and starts the Dispatcher on that thread. That is the minimum requirements to get a Window displaying and handling messages correctly, but, unfortunately, has some serious flaws. The first issue – the created thread will run continuously until the application shuts down, given the code in the sample.  The problem is that the ThreadStart delegate used ends with running the Dispatcher.  However, nothing ever stops the Dispatcher processing.  The thread was created as a Background thread, which prevents it from keeping the application alive, but the Dispatcher will continue to pump dispatcher frames until the application shuts down. In order to fix this, we need to call Dispatcher.InvokeShutdown after the Window is closed.  This would require modifying the above sample to subscribe to the Window’s Closed event, and, at that point, shutdown the Dispatcher: // Create a thread Thread newWindowThread = new Thread(new ThreadStart( () => { Window1 tempWindow = new Window1(); // When the window closes, shut down the dispatcher tempWindow.Closed += (s,e) => Dispatcher.CurrentDispatcher.BeginInvokeShutdown(DispatcherPriority.Background); tempWindow.Show(); // Start the Dispatcher Processing System.Windows.Threading.Dispatcher.Run(); })); // Setup and start thread as before This eliminates the first issue.  Now, when the Window is closed, the new thread’s Dispatcher will shut itself down, which in turn will cause the thread to complete. The above code will work correctly for most situations.  However, there is still a potential problem which could arise depending on the content of the Window1 class.  This is particularly nasty, as the code could easily work for most windows, but fail on others. The problem is, at the point where the Window is constructed, there is no active SynchronizationContext.  This is unlikely to be a problem in most cases, but is an absolute requirement if there is code within the constructor of Window1 which relies on a context being in place. While this sounds like an edge case, it’s fairly common.  For example, if a BackgroundWorker is started within the constructor, or a TaskScheduler is built using TaskScheduler.FromCurrentSynchronizationContext() with the expectation of synchronizing work to the UI thread, an exception will be raised at some point.  Both of these classes rely on the existence of a proper context being installed to SynchronizationContext.Current, which happens automatically, but not until Dispatcher.Run is called.  In the above case, SynchronizationContext.Current will return null during the Window’s construction, which can cause exceptions to occur or unexpected behavior. Luckily, this is fairly easy to correct.  We need to do three things, in order, prior to creating our Window: Create and initialize the Dispatcher for the new thread manually Create a synchronization context for the thread which uses the Dispatcher Install the synchronization context Creating the Dispatcher is quite simple – The Dispatcher.CurrentDispatcher property gets the current thread’s Dispatcher and “creates a new Dispatcher if one is not already associated with the thread.”  Once we have the correct Dispatcher, we can create a SynchronizationContext which uses the dispatcher by creating a DispatcherSynchronizationContext.  Finally, this synchronization context can be installed as the current thread’s context via SynchronizationContext.SetSynchronizationContext.  These three steps can easily be added to the above via a single line of code: // Create a thread Thread newWindowThread = new Thread(new ThreadStart( () => { // Create our context, and install it: SynchronizationContext.SetSynchronizationContext( new DispatcherSynchronizationContext( Dispatcher.CurrentDispatcher)); Window1 tempWindow = new Window1(); // When the window closes, shut down the dispatcher tempWindow.Closed += (s,e) => Dispatcher.CurrentDispatcher.BeginInvokeShutdown(DispatcherPriority.Background); tempWindow.Show(); // Start the Dispatcher Processing System.Windows.Threading.Dispatcher.Run(); })); // Setup and start thread as before This now forces the synchronization context to be in place before the Window is created and correctly shuts down the Dispatcher when the window closes. However, there are quite a few steps.  In my next post, I’ll show how to make this operation more reusable by creating a class with a far simpler API…

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  • WPF Dispatcher {"The calling thread cannot access this object because a different thread owns it."}

    - by user359446
    first I need to say that I´m noob with WPF and C#. Application: Create Mandelbrot Image (GUI) My disptacher works perfektly this this case: private void progressBarRefresh(){ while ((con.Progress) < 99) { progressBar1.Dispatcher.Invoke(DispatcherPriority.Send, new Action(delegate { progressBar1.Value = con.Progress; } )); } } I get the Message (Title) when tring to do this with the below code: bmp = BitmapSource.Create(width, height, 96, 96, pf, null, rawImage, stride); this.Dispatcher.Invoke(DispatcherPriority.Send, new Action(delegate { img.Source = bmp; ViewBox.Child = img; //vllt am schluss } )); I will try to explain how my program works. I created a new Thread (because GUI dont response) for the calculation of the pixels and the colors. In this Thread(Mehtod) I´m using the Dispatcher to Refresh my Image in the ViewBox after the calculations are ready. When I´m dont put the calculation in a seperate Thread then I can refresh or build my Image.

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  • C# Dispatcher {"The calling thread cannot access this object because a different thread owns it."}

    - by user359446
    Hi, first I need to say that I´m noob with WPF and C#. Application: Create Mandelbrot Image (GUI) My disptacher works perfektly this this case: private void progressBarRefresh(){ while ((con.Progress) < 99) { progressBar1.Dispatcher.Invoke(DispatcherPriority.Send, new Action(delegate { progressBar1.Value = con.Progress; } )); } } I get the Message (Title) when tring to do this with the below code: bmp = BitmapSource.Create(width, height, 96, 96, pf, null, rawImage, stride); this.Dispatcher.Invoke(DispatcherPriority.Send, new Action(delegate { img.Source = bmp; ViewBox.Child = img; //vllt am schluss } )); I will try to explain how my program works. I created a new Thread (because GUI dont response) for the calculation of the pixels and the colors. In this Thread(Mehtod) I´m using the Dispatcher to Refresh my Image in the ViewBox after the calculations are ready. When I´m dont put the calculation in a seperate Thread then I can refresh or build my Image. PS: Sry for my bad english

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