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WPF framework using Dispatcher.CurrentDispatcher in background thread, causing memory leak

I'm using a WPF CollectionView and I'm setting the Filter in a background thread, because it takes a long time to apply this filter.
Setting this Filter triggers the method ScheduleMapCleanup() of CollectionView (so WPF framework code I can't change). In this method, Dispatcher.CurrentDispatcher.BeginInvoke is used.
However, because this is executed in a background thread, this Action is never executed (the Dispatcher of this thread is never started), causing a memory leak: The Dispatcher keeps a reference to the CollectionView.
How could I work around this problem? Setting the Filter in the UI thread is not an option.
Could I start the Dispatcher myself? If so, how do I do this (Dispatcher.Run halts everything)?

I use this when I need to update some controls and binding on my UI thread from my background tasks:
Application.Current.Dispatcher.Invoke(
DispatcherPriority.Loaded,
new Action(() => {
// Code here
})
);
If it's not this can you be more specific on what you want to do on your UI thread

Accessing the current dispatcher from a background thread does not give you the UI dispatcher, it gives you a new one for the background thread.
Either call CurrentDispatcher from the foreground thread and pass the result to the background thread, or call DependencyObject.Dispatcher to get the dispatcher for a window or other control.
Edit: I just read the question more closely. Since you do not control the code calling CurrentDispatcher, the only way that it will work is to call that code from the UI thread.

To be clear: I don't use Dispatcher.CurrentDispatcher in my code. This is used in the WPF framework code, so I can't change this.
This code is executed in a background thread because I'm setting the Filter in a background thread. I'm setting this property in a background thread because it can take up to several minutes. Setting it in a background thread keeps the UI responsive and lets me show a loading indication to the user.
I fixed the memory leak (caused by the not-running background Dispatcher keeping a reference to the CollectionView) by adding a Shutdown to the Dispatcher and starting the dispatcher in the background thread:
//All code below is executed on a background thread
//Line below causes WPF framework to add something to Dispatcher.CurrentDispatcher queue.
view.Filter = new Predicate<Object>(actionTarget.FilterCallback);
if (Thread.CurrentThread.IsBackground && Dispatcher.CurrentDispatcher != Application.Current.Dispatcher)
{
Dispatcher.CurrentDispatcher.BeginInvokeShutdown(DispatcherPriority.Background);
Dispatcher.Run();
}
If the background thread is reused later (for example because it's a thread pool thread, started by a BackgroundWorker) you can't use BeginInvokeShutdown like in the code above: a shut down dispatcher can not be started again. In that case, use this instead of the BeginInvokeShutdown:
Dispatcher.CurrentDispatcher.BeginInvoke((Action) delegate() { Dispatcher.ExitAllFrames(); }, DispatcherPriority.Background);
This will make sure the Run() method returns, but the dispatcher can be started again later on.
Edit: As Mitch mentioned in comment below, be carefull when multiple threads can be executing the Run() at the same time. If necessary add a lock around the Run().

Executing Code behind before Xaml Rendering - How to influence the sequence

I'm working on a Windows Phone App.
I have a very performance intensive method which takes several seconds until the operation is done.
When the method is called I want to show an animated loading symbol which is defined in the xaml of my view. When the operation is finished it should disappear. I set the loading symbol to visible in the first line of this method.In the last line I set the visibility to collapsed.
The problem is that at first the whole code behind will be executed. Unfortunately nothing is to be seen, because the the visibiliy is set to visible after the code behind operations are executed and in the same moment its set to collapsed.
Has anybody an idea how to solve this problem? Thanks so much in advance.

The problem you have is that you're calling your method on the main (UI) thread. This means that your method blocks the UI from refreshing, and also means that (as you noted) by the time the UI does refresh, you've already hidden the icon again.
What you need to do instead is call your method on a background thread (there are a number of ways to handle this). You will need to push the UI update to the UI thread (using Dispatcher.Invoke), but the rest of your method will run on a separate thread.
You'll also need to use a callback of some kind - maybe a custom event - so that your UI thread knows when the background thread is completed.

Without seeing the code its hard to say for sure but if you use the dispatcher to run you intensive code after the busy indicator is set this would allow the ui thread time to change before running the code.
An example
//This assumes you are binding in xaml to the isbusy and it implements INotifyPropertyChanged
IsBusy = true;
Dispatcher.BeginInvoke(()=>{ //...performance intense here
});
That being Said Dan Puzey is right. You should only run this logic on the UI thread if for some reason your need to. even then be wary of this as it makes for a poor ui experience.
One way you could accomplish this and still have your dispatcher fire off when you need would be to pass a copy of the dispatcher into the background.
ThreadPool.QueueUserWorkItem (d => {
//...performance intense here
Dispatcher dispatcher = d as Dispatcher;
if(dispatcher != null){
dispatcher.BeginInvoke()()=>{//...ui updates here }
}
}, Dispatcher.CurrentDispatcher);//make sure this is called from your UI thread or you may not end up with the correct dispatcher

Progress dialog on a heavy loaded UI thread does not get updated when binding changes

While maintaining an old MFC application we have implemented a new progress dialog bar in WPF. The application currently has the UI thread busy with a lot of business operations but changing this is out of scope.
When a string property changes its value (binded to the text of a TextBox) the progress dialog does not get refreshed (only sometimes when the thread is not so busy).
As far as I know as the update of the property is done from the UI thread the thread should be able to update the dialog and repaint it before going on the next thing so I don't get why it's not being updated and how to fix it.
Any ideas?
EDIT: What are the drawbacks of this solution, I have tried it and seems to work fine:
private static Action EmptyDelegate = delegate() { };
public static void Refresh(this UIElement uiElement)
{
uiElement.Dispatcher.Invoke(DispatcherPriority.Render, EmptyDelegate);
}

I found out the solution here:
http://eprystupa.wordpress.com/2008/07/28/running-wpf-application-with-multiple-ui-threads/
Then I created a new thread with the progress dialog.

The application currently has the UI thread busy with a lot of business operations
Well there's your problem. You shouldn't be doing that. You ought to be performing long running operations in a non-UI thread. It's the reason why updates to the UI aren't made until after the long running operation finishes.
You can use a BackgroundWorker to help simplify interactions with a UI while performing a long running task, as it will handle marshaling to the UI thread for the progress updated and completed event handlers.

First, I agree with #Servy, you shouldn't do heavy work in the UI thread.
However, if you cannot do the work in another thread, you can consider spawning another one for your dialog. I don't know how you are calling the wpf window, but this link may give you some clues about how it would be done in C#.

Form Visiblity Problem

Form1.button_Click(...) {
// Show a dialog form, which runs a method <CheckBalance()> on it's OnLoad Event.
var modemDialog = new ModemDialog("COM25");
modemDialog.ShowDialog();
// the user can't see this dialog form until the method <CheckBalance()> terminates.
}
Is it possible to show first the dialog then run the specified method?
THanks.

That is correct and expected. Winforms UI is inherently single-threaded. Having a function call like "CheckBalance" in the form load event will prevent the form from showing until the form load event completes. Depending on the duration of the task, you have a number of options available to you:
If it's a fast task, compute it ahead of time before showing the form
If it's something the user may want to initiate, move it to a button on the new form, so it's only calculated on the request of the user
If it's a long running task that takes some time, you'll need to move it off in to another thread. Using a BackgroundWorker is recommended.

OnLoad occurs before the form is shown to allow you to initialise the form and variables and what not, which means it is synchronous. The form will not show until you return from that function.
If you want to asynchronously run the CheckBalance() method, then you can use a few techniques, such as utilising the Threading, ThreadPool or Tasks API to shift that work to a background thread, and returning immediately so that the form is shown.
Here is an example of using a Task to perform the same action, but asynchronously so that the form immediately shows:
Action<object> action = () => { CheckBalance(); };
new Task(action).Start();
Please note that if you access the UI thread, you'll need to beware of thread-safety and invocation.

The simple way to make sure your form is visible before CheckBalance is run is to use this code in the form load handler:
this.BeginInvoke((Action)(() => this.CheckBalance()));
This will push the execution of the CheckBalance method onto the UI thread message pump so will execute after all preceding UI code is complete.
Others are correct though that the UI will still be blocked as CheckBalance executes. You probably want to run it on a background thread to prevent this.

WinForm And Looping

I have a WinForm set up and a process that loops until a button is pressed on the form.
When I try to run my code, the form does not even display. I suspect this is because the code gets stuck in the loop and doesn't get far enough to display the WinForm. How can I get the form to display and the loop to run after that point?

If you're looping because you need to do something with the GUI periodically while waiting for input, I suggest using a Timer control and its Tick event.
If you want to do non-GUI things while waiting, a more traditional timer is better suited to the task,

You should probably run the loop in a background thread. The BackgroundWorker class makes this pretty easy to do.

Don't do that.
Windows Forms (like most modern user interface development toolkits) is an event-driven framework. You should never use a loop that "waits" for something to happen; instead you want to use an event that triggers something to happen.
Essentially what's happening is this: WinForms has a loop running a message pump that listens for events from Windows and triggers C# events in response to them. Your code is executing on the same thread as that message pump (it has to, since in WinForms only one thread is allowed to touch any given control). So if you put that thread into a loop, the WinForms code that should be pumping messages isn't, and your user interface appears to hang, since it isn't responding to any messages from Windows. (If you keep clicking it, you will fill up the message queue and get a dialog box that says "This application has stopped responding, do you want to terminate?" or something like that.)
The correct solution is to do one of the following:
Use a Timer
Use a BackgroundWorker
Use a ThreadPool
Another solution that would work, but is not a good idea is:
Use Application.DoEvents() -- but please don't actually do this

Your form loading is freezing because the UI of a windows form runs in a single thread. And the logic that you put on the Load event of this form is running on that thread.
You can run your loop on a separate thread easily by using a BackgroundWorker component on your windows form. On the event DoWork of your background worker, you place the code that has the loop that should run without block your UI. On the Form.Load event, you can start the background worker component by calling the method RunWorkerAsync. On the event handler of your button, you place a code to stop the background worker by calling CancelAsync method.
The article How to: Implement a Form That Uses a Background Operation shows exactly how to accomplish it.
About your comment on not being able to update the Text of a TextBox from a your background worker component. It happens because it is not allowed to modify the state of a windows forms control from a different thread (your background worker code is running on a separated thread) MSDN documentation says:
Access to Windows Forms controls is not inherently thread safe. If you have two or more threads manipulating the state of a control, it is possible to force the control into an inconsistent state. Other thread-related bugs are possible, such as race conditions and deadlocks. It is important to make sure that access to your controls is performed in a thread-safe way.
A sample of how you can update the state of your windows forms controls from your background thread will be similar to the one below (assuming that the new value is already stored on a String variable named 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.textBox1.InvokeRequired)
{
SetTextCallback d = new SetTextCallback(SetText);
this.Invoke(d, new object[] { text });
}
else
{
this.textBox1.Text = text;
}
I borrowed this code snipped from How to: Make Thread-Safe Calls to Windows Forms Controls article. It can provide you more information about how to deal with multi-threaded windows forms.

You can use the form load event to trigger the start of the loop.
So it would handle the event Me.Load
However is it necessary for your loop to be happening inside of the UI?

This happens because your loop is keeping the window function from processing messages, such as those that tell it to repaint itself. Place a call to Application.DoEvents() inside of your loop to allow the UI to continue to function.
However, you need to ask yourself why you're looping like this in the first place. If you're, say, copying a bunch of files, this might make sense. For most tasks, though, responding to a timer tick should do the trick and won't block the UI.

You should run your loop in a background thread using the BackgroundWorker component.
Remember that the background thread cannot directly interact with the UI controls.
To report the progress on the UI, you should call the BackgroundWorker's ReportProgress method in the background thread, and handle the ProgressChanged event to update the UI.
You can call the CancelAsync method when the Button is clicked, and loop until the CancellationPending property is true.