Unable to clear memory in C++ Managed application

Question

I have written a win32 project and it internally calls C# forms(using /clr) to do few tasks. 
Once the task is completed, the form is closed. But the problem is what ever memory is allocated after loading C# form is not getting cleaned up. I tried GC.Collect() in C# code to force the cleanup, but of no use.
Can anyone help me in resolving the issue?
C# code:public void close()
GC.Collect();
GC.WaitForPendingFinalizers();
GC.Collect();
C++ code:
frm = gcnew libry::Form1();
frm->ShowDialog();
frm->close();
delete frm;
frm = nullptr;
- Shiva.

Answer 1

The memory allocated with gcnew in C++/CLR or with new in C# does not have to be freed programmatically, since it is managed by the system. If you need an explicit management, then also call
WaitForFullGCComplete before WaitForPendingFinalizers.
Memory leaks can be caused by incorrect management of native resources, such as allocations with
new or malloc in C++, which are not freed in the finaliser, which is a special member defined with “!”:
https://msdn.microsoft.com/en-us/library/ms177197(v=vs.100).aspx.
False leaks can be caused by missing using statements in C# or missing calls of
Dispose().
Do you really need to call Collect explicitly and do you have some suspicious native resources?