My code:

Image img = new Image();

BitmapImage bi = new BitmapImage();
bi.BeginInit();
bi.UriSource = new Uri(@"C:\Documents and Settings\All Users\Documents\My Pictures\Sample Pictures\Water lilies.jpg");
bi.EndInit();
img.Source = bi;
btn1.ToolTip = img; //btn1 is a Button

Symptom:

Every time when the tooltip of "btn1" shows, some memory is consumed and will not be released later.

So, is it the problem of my code or the winfx?

Thanks a lot.

I don't think that's a WinFX problem. I believe that, as long as the btn1 element exists, its property value (in this case, the bitmap image) is stored in memory.

So, if you really want it gone, set btn1.tooltip=null when the tooltip closes. Then that variable will get munched up by the GC. when it loses scope (i.e. when the method ends).

By default, the BitmapCacheOption is set ot "OnDemand". This means that the image will be held onto since we need to be able to get to the image bits. Can you try the following and see if this helps:

Image img = new Image();

BitmapImage bi = new BitmapImage();
bi.BeginInit();
bi.UriSource = new Uri(@"C:\Documents and Settings\All Users\Documents\My Pictures\Sample Pictures\Water lilies.jpg");

bi.CacheOption = BitmapCacheOption.OnLoad;
bi.EndInit();
img.Source = bi;
btn1.ToolTip = img; //btn1 is a Button