That's how I reproduce the bug :

Refresh only the master template, the memory is steady. After I expanded all child templates, the memory will increase heavily (it's normal.). And also the gridview control does lots of GC collect after hierarchy refresh. Part of the memory resource can be recycled. But globally, the memory increases.

And then, if I collapse all child templates, keep only the master template refreshing. The memory cannot go back to the level at the first place. But it remains stable.

Thank you for your help.