Question

I have a problem with a memory leak in a .NET CF application.

Using RPM I identified that dynamically creating controls are not garbage collected as expected. Running the same piece of code in .NET Window Forms behave differently and disposes the control as I expected.

See the output from RPM via PerfMon for the Process Heap counter:

GC Heap:

My best guess is that the Weak Reference to the Panel is for some unknown reason not making the object eligible for GC, can it be?

Please note: Even though Dispose() solves the problem for the sample, I can’t easily incorporate it into the existing application as it is not as clear cut to determine when the object is no longer in use.

I have included a simplified version of the source to illustrate the problem:

using System; using System.Windows.Forms;  namespace CFMemTest {     public partial class Form1 : Form     {         public Form1()         {             InitializeComponent();         }          // Calling this event handler multiple times causes the memory leak         private void Button1_Click(object sender, EventArgs e)         {             Panel uc = new Panel();             // Calling uc.Dispose() cleans up the object          }     } } 

Update:
1. Calling GC.Collect() also doesn’t result in the panels being cleaned up.
2. Using .NET CF 2.0 SP1 on a Windows CE 4.2 device.

Answer 1

Some additional information here that explains this behaviour.

According to Ilya Tumanov:

Everything UI related on NETCF is intentionally removed from GC scope so it is never collected. This behavior is different from desktop and has been changed in NETCF V3.5 (unless running in compatibility mode).

It is so different because managed UI classes on NETCF are completely different from desktop. They are thin wrappers over native implementation which was needed to achieve acceptable performance.

I’m not sure there’s such a resource. But really, all you need to know is: it’s never collected, must call dispose. You actually should do that on desktop as well but if you don’t its way more forgiving. Not so on NETCF.