How To make certain that a page is removed from memory, silverlight

Question


Hello,
I have a big solution with several branches. These branches was tested individually for errors and memory issues, using VS profiler and debugger. A final solution was found that at highest with animations and music peaked to 100mb, of course high but should
not be an issue for Windows phone applications, even for low end devices. The branches was then collected to one main branch. A new test was run, and suddenly the memory spiked up towards 200mb and crashed on phones and emulators with out of memory exception.
We at the team then tried:
protected override void OnNavigatedTo(NavigationEventArgs e)
if (App.RootFrame.CanGoBack)
App.RootFrame.RemoveBackEntry();
GC.Collect();
base.OnNavigatedTo(e);
This was discussed on forums to help with page memory leakage, this however did not solve the issue. We therefore wanted to investigate if pages and other elements got deconstructed and GC.Collected. This we did by implementing deconstructors:
~SecondScreen()
In_Game_Crest = null;
currentViewModel = null;
This confirmed our fears that the pages, popups and controls did not get garbage collected, even if we sat everything to null, or
set everything to private functions. Our code is implemented in a MVVM structure, we therefore looked to ViewModelLocator, and removed the servicelocator, as to force a new viewmodel creation for every page creation.
This showed that the viewmodels got garbage collected upon navigation, but the views and usercontrols did not. We therefore searched around for the issue and found some links that could help us, referring to IDisposable, we therefore tried with the following
implementation:
private bool disposed = false;
public void Dispose()
Dispose(true);
// Take yourself off the Finalization queue
// to prevent finalization code for this object
// from executing a second time.
GC.SuppressFinalize(this);
protected virtual void Dispose(bool disposing)
// Check to see if Dispose has already been called.
if(!this.disposed)
// If disposing equals true, dispose all managed
// and unmanaged resources.
if(disposing)
// Dispose managed resources.
currentView = null;
popup = null;
Image1 = null;
Image2 = null;
// Release unmanaged resources. If disposing is false,
// only the following code is executed.
this.Content = null;
// Note that this is not thread safe.
// Another thread could start disposing the object
// after the managed resources are disposed,
// but before the disposed flag is set to true.
// If thread safety is necessary, it must be
// implemented by the client.
disposed = true;
// Use C# destructor syntax for finalization code.
// This destructor will run only if the Dispose method
// does not get called.
// It gives your base class the opportunity to finalize.
// Do not provide destructors in types derived from this class.
~FirstPage()
Dispose(false);
protected override void OnNavigatedFrom(NavigationEventArgs e)
this.Dispose();
base.OnNavigatedFrom(e);
This however only increased the memory usage by 20 mb, for every call to dispose. Which hopefully would mean that we have misunderstood the use of IDisposable.
Questions:
Therefore quite confused, I have learned from my similar question on Stackoverflow, that I should use the VS profiler more intently to find references, but I have not succeeded in finding anything with the profiler. And I do not understand why the
deconstructors are not fired when I know no references exists.
Therefore would it help to implement IDisposable and how should it be done in a windows phone Silverlight context?
Should I do something specific when I utilize the MVVM structure?Any proposals on how to force the deletion and how to do the deletion correctly?
Or is there some other way to go about it, to ensure that pages with all information is removed.
Hope for any help, If you want stackoverflow points I also have the following: stackoverflow.com/questions/27744091/implementing-dispose-and-finalize-for-windows-phone-silverlight-pages/

Answer 1

One way i can suggest is to use 'Using' statement(obviously if not already did that) wherever it is required to work with resources such as opening a connection to database, file operations etc. With this, the resources are disposed automatically as soon
as 'Using' block goes out of scope.
e.g.
using (StreamReader reader = new StreamReader("somefile.txt"))
your code
http://developer.nokia.com/community/wiki/Using_Crypto%2B%2B_library_with_Windows_Phone_8