处置和存储流

Question

I have the following code that gets called 4 times a second and updates the background of a grid. When i don't dispose of of the memory stream, the memory output usage slowly grows and falls. MemoryStream has a Dispose function, But if I call it even after i dispose the Source Bitmap, the background is just white.

Do i need to dispose the stream? And if I do, what am I doing wrong?

private void Viewer_OnUpdate(object self, Bitmap sourceBitmap, Int32Rect cropArea)
    {
        if (sourceBitmap == null)
        {
            return;
        }

        this.Dispatcher.BeginInvoke(DispatcherPriority.Render,
            new Action(
                () =>
                    {
                        MemoryStream stream = new MemoryStream();
                        sourceBitmap.Save(stream, ImageFormat.Bmp);
                        BitmapImage bitmapImage = new BitmapImage();
                        bitmapImage.BeginInit();
                        stream.Seek(0, SeekOrigin.Begin);
                        bitmapImage.StreamSource = stream;
                        bitmapImage.EndInit();
                        this.GridContainer.Background =
                            new ImageBrush(new CroppedBitmap(bitmapImage,cropArea));
                        sourceBitmap.Dispose();
                    }));
    }

Note: i'm dispatching because the calling event is always from a Non-UI thread

Answer 1

From MSDN documentation for BitmapImage (emphasis is mine):

Set the CacheOption property to BitmapCacheOption.OnLoad if you wish to close the stream after the BitmapImage is created . The default OnDemand cache option retains access to the stream until the bitmap is needed, and cleanup is handled by the garbage collector.

Answer 2

First, you discovered that if you dispose the memory stream, the bitmap is affected, which means your ImageBrush seems white. So - don't dispose the memory stream.

Second, and more importantly, the memory consumption pattern you're seeing - more and more memory, then a sudden fall - is normal. That's what happens when the garbage collector runs at its own discretion. It's not a problem at all.

So don't dispose of the memory stream, let the garbage collector do its job, and don't worry about it.

Answer 3

Look, maybe this answer will help you.

MemoryStream in Using Statement - Do I need to call close()

If you put your MemoryStream in a using statement, you will not need to Dispose, because it will do it automatically ;)

I hope this helps