I have been trying to build a Finder like app. The folders has been mounted in the outline view successfully, but however when trying to operate on it, it crashes from time to time. Sometimes, i just click on the arrow to expand a node, or sometimes just while scrolling the tree.

Here is what i get:

Loaded assembly: /Users/Kevin/Desktop/TESTproj/TESTproj/bin/Debug/TESTproj.app/Contents/MonoBundle/TESTproj.exe
Loaded assembly: /Users/Kevin/Desktop/TESTproj/TESTproj/bin/Debug/TESTproj.app/Contents/MonoBundle/Xamarin.Mac.dll [External]
Loaded assembly: /Users/Kevin/Desktop/TESTproj/TESTproj/bin/Debug/TESTproj.app/Contents/MonoBundle/System.Core.dll [External]
Loaded assembly: ObjCImplementations [External]
Resolved pending breakpoint at 'MainWindowController.cs:238,1' to void TESTproj.MainWindowController.OnPathAction (Foundation.NSObject sender) [0x00007].
Stacktrace:

at <0xffffffff>
at (wrapper managed-to-native) AppKit.NSApplication.NSApplicationMain (int,string[])
at AppKit.NSApplication.Main (string[]) [0x00041] in /Users/builder/data/lanes/1408/d6c95235/source/xamcore/src/AppKit/NSApplication.cs:105
at TESTproj.MainClass.Main (string[]) [0x00007] in /Users/Kevin/Desktop/TESTproj/TESTproj/Main.cs:14
at (wrapper runtime-invoke) .runtime_invoke_void_object (object,intptr,intptr,intptr)

Native stacktrace:

Debug info from gdb:

(lldb) command source -s 0 '/tmp/mono-gdb-commands.yeLMu0'
Executing commands in '/private/tmp/mono-gdb-commands.yeLMu0'.
(lldb) process attach --pid 1333
Process 1333 stopped
Executable module set to "/Users/Kevin/Desktop/TESTproj/TESTproj/bin/Debug/TESTproj.app/Contents/MacOS/TESTproj".
Architecture set to: x86_64h-apple-macosx.
(lldb) thread list
Process 1333 stopped
* thread #1: tid = 0x138c3, 0x00007fff8abd5902 libsystem_kernel.dylib

__wait4 + 10, queue = 'com.apple.main-thread', stop reason = signal SIGSTOP
  thread #2: tid = 0x138e2, 0x00007fff8abd6232 libsystem_kernel.dylib

kevent64 + 10, queue = 'com.apple.libdispatch-manager'
thread #3: tid = 0x138e4, 0x00007fff8abd594a libsystem_kernel.dylib

__workq_kernreturn + 10
  thread #4: tid = 0x138e6, 0x00007fff8abd051a libsystem_kernel.dylib

semaphore_wait_trap + 10
thread #5: tid = 0x138e7, 0x00007fff8abd533a libsystem_kernel.dylib

__recvfrom + 10
  thread #6: tid = 0x138e9, 0x00007fff8abd594a libsystem_kernel.dylib

__workq_kernreturn + 10
thread #7: tid = 0x138eb, 0x00007fff8abd594a libsystem_kernel.dylib

__workq_kernreturn + 10
  thread #8: tid = 0x138ec, 0x00007fff8abd594a libsystem_kernel.dylib

__workq_kernreturn + 10
thread #9: tid = 0x138f5, 0x00007fff8abd594a libsystem_kernel.dylib

__workq_kernreturn + 10
  thread #10: tid = 0x13901, 0x00007fff8abd594a libsystem_kernel.dylib

__workq_kernreturn + 10
thread #11: tid = 0x13902, 0x00007fff8abd594a libsystem_kernel.dylib

__workq_kernreturn + 10
  thread #12: tid = 0x13903, 0x00007fff8abd594a libsystem_kernel.dylib

__workq_kernreturn + 10
thread #13: tid = 0x13904, 0x00007fff8abd594a libsystem_kernel.dylib

__workq_kernreturn + 10
  thread #14: tid = 0x13914, 0x00007fff8abd04de libsystem_kernel.dylib

mach_msg_trap + 10
(lldb) thread backtrace all
* thread #1: tid = 0x138c3, 0x00007fff8abd5902 libsystem_kernel.dylib

__wait4 + 10, queue = 'com.apple.main-thread', stop reason = signal SIGSTOP
  * frame #0: 0x00007fff8abd5902 libsystem_kernel.dylib

__wait4 + 10
frame #1: 0x00000001000d75f1 TESTproj

mono_handle_native_sigsegv(signal=<unavailable>, ctx=<unavailable>) + 433 at mini-exceptions.c:2323
    frame #2: 0x0000000100055cc7 TESTproj

mono_arch_handle_altstack_exception(sigctx=0x00000001004fcf48, fault_addr=, stack_ovf=0) + 87 at exceptions-amd64.c:902
frame #3: 0x00000001000f07b6 TESTproj

mono_sigsegv_signal_handler(_dummy=<unavailable>, info=<unavailable>, context=<unavailable>) + 374 at mini.c:6860
    frame #4: 0x00007fff8be8cf1a libsystem_platform.dylib

_sigtramp + 26
frame #5: 0x00007fff948550ea libobjc.A.dylib`objc_msgSend + 42

thread #2: tid = 0x138e2, 0x00007fff8abd6232 libsystem_kernel.dylib

kevent64 + 10, queue = 'com.apple.libdispatch-manager'
    frame #0: 0x00007fff8abd6232 libsystem_kernel.dylib

kevent64 + 10
frame #1: 0x00007fff915f8d91 libdispatch.dylib

_dispatch_mgr_invoke + 247
    frame #2: 0x00007fff915f8a6a libdispatch.dylib

_dispatch_mgr_thread + 52

thread #3: tid = 0x138e4, 0x00007fff8abd594a libsystem_kernel.dylib

__workq_kernreturn + 10
    frame #0: 0x00007fff8abd594a libsystem_kernel.dylib

__workq_kernreturn + 10
frame #1: 0x00007fff8c6886c3 libsystem_pthread.dylib

_pthread_wqthread + 869
    frame #2: 0x00007fff8c68640d libsystem_pthread.dylib

start_wqthread + 13

thread #4: tid = 0x138e6, 0x00007fff8abd051a libsystem_kernel.dylib

semaphore_wait_trap + 10
    frame #0: 0x00007fff8abd051a libsystem_kernel.dylib

semaphore_wait_trap + 10
frame #1: 0x0000000100208737 TESTproj

mono_sem_wait(sem=0x0000000100380028, alertable=1) + 23 at mono-semaphore.c:103
    frame #2: 0x000000010013b318 TESTproj

finalizer_thread(unused=) + 88 at gc.c:1077
frame #3: 0x00000001001d25fe TESTproj

start_wrapper [inlined] start_wrapper_internal + 386 at threads.c:660
    frame #4: 0x00000001001d247c TESTproj

start_wrapper(data=) + 44 at threads.c:707
frame #5: 0x00000001002091ae TESTproj

inner_start_thread(arg=<unavailable>) + 222 at mono-threads-posix.c:100
    frame #6: 0x000000010022c123 TESTproj

GC_start_routine(arg=) + 83 at pthread_support.c:1502
frame #7: 0x00007fff8c688268 libsystem_pthread.dylib

_pthread_body + 131
    frame #8: 0x00007fff8c6881e5 libsystem_pthread.dylib

_pthread_start + 176
frame #9: 0x00007fff8c68641d libsystem_pthread.dylib`thread_start + 13

thread #5: tid = 0x138e7, 0x00007fff8abd533a libsystem_kernel.dylib

__recvfrom + 10
    frame #0: 0x00007fff8abd533a libsystem_kernel.dylib

__recvfrom + 10
frame #1: 0x0000000100045e39 TESTproj

socket_transport_recv(buf=0x0000000102a03e05, len=11) + 121 at debugger-agent.c:1131
    frame #2: 0x0000000100036b13 TESTproj

debugger_thread [inlined] transport_recv(len=) + 33 at debugger-agent.c:1557
frame #3: 0x0000000100036af2 TESTproj

debugger_thread(arg=<unavailable>) + 642 at debugger-agent.c:9551
    frame #4: 0x00000001002091ae TESTproj

inner_start_thread(arg=) + 222 at mono-threads-posix.c:100
frame #5: 0x000000010022c123 TESTproj

GC_start_routine(arg=<unavailable>) + 83 at pthread_support.c:1502
    frame #6: 0x00007fff8c688268 libsystem_pthread.dylib

_pthread_body + 131
frame #7: 0x00007fff8c6881e5 libsystem_pthread.dylib

_pthread_start + 176
    frame #8: 0x00007fff8c68641d libsystem_pthread.dylib

thread_start + 13

thread #6: tid = 0x138e9, 0x00007fff8abd594a libsystem_kernel.dylib

__workq_kernreturn + 10
    frame #0: 0x00007fff8abd594a libsystem_kernel.dylib

__workq_kernreturn + 10
frame #1: 0x00007fff8c6886c3 libsystem_pthread.dylib

_pthread_wqthread + 869
    frame #2: 0x00007fff8c68640d libsystem_pthread.dylib

start_wqthread + 13

thread #7: tid = 0x138eb, 0x00007fff8abd594a libsystem_kernel.dylib

__workq_kernreturn + 10
    frame #0: 0x00007fff8abd594a libsystem_kernel.dylib

__workq_kernreturn + 10
frame #1: 0x00007fff8c6886c3 libsystem_pthread.dylib

_pthread_wqthread + 869
    frame #2: 0x00007fff8c68640d libsystem_pthread.dylib

start_wqthread + 13

thread #8: tid = 0x138ec, 0x00007fff8abd594a libsystem_kernel.dylib

__workq_kernreturn + 10
    frame #0: 0x00007fff8abd594a libsystem_kernel.dylib

__workq_kernreturn + 10
frame #1: 0x00007fff8c6886c3 libsystem_pthread.dylib

_pthread_wqthread + 869
    frame #2: 0x00007fff8c68640d libsystem_pthread.dylib

start_wqthread + 13

thread #9: tid = 0x138f5, 0x00007fff8abd594a libsystem_kernel.dylib

__workq_kernreturn + 10
    frame #0: 0x00007fff8abd594a libsystem_kernel.dylib

__workq_kernreturn + 10
frame #1: 0x00007fff8c6886c3 libsystem_pthread.dylib

_pthread_wqthread + 869
    frame #2: 0x00007fff8c68640d libsystem_pthread.dylib

start_wqthread + 13

thread #10: tid = 0x13901, 0x00007fff8abd594a libsystem_kernel.dylib

__workq_kernreturn + 10
    frame #0: 0x00007fff8abd594a libsystem_kernel.dylib

__workq_kernreturn + 10
frame #1: 0x00007fff8c6886c3 libsystem_pthread.dylib

_pthread_wqthread + 869
    frame #2: 0x00007fff8c68640d libsystem_pthread.dylib

start_wqthread + 13

thread #11: tid = 0x13902, 0x00007fff8abd594a libsystem_kernel.dylib

__workq_kernreturn + 10
    frame #0: 0x00007fff8abd594a libsystem_kernel.dylib

__workq_kernreturn + 10
frame #1: 0x00007fff8c6886c3 libsystem_pthread.dylib

_pthread_wqthread + 869
    frame #2: 0x00007fff8c68640d libsystem_pthread.dylib

start_wqthread + 13

thread #12: tid = 0x13903, 0x00007fff8abd594a libsystem_kernel.dylib

__workq_kernreturn + 10
    frame #0: 0x00007fff8abd594a libsystem_kernel.dylib

__workq_kernreturn + 10
frame #1: 0x00007fff8c6886c3 libsystem_pthread.dylib

_pthread_wqthread + 869
    frame #2: 0x00007fff8c68640d libsystem_pthread.dylib

start_wqthread + 13

thread #13: tid = 0x13904, 0x00007fff8abd594a libsystem_kernel.dylib

__workq_kernreturn + 10
    frame #0: 0x00007fff8abd594a libsystem_kernel.dylib

__workq_kernreturn + 10
frame #1: 0x00007fff8c6886c3 libsystem_pthread.dylib

_pthread_wqthread + 869
    frame #2: 0x00007fff8c68640d libsystem_pthread.dylib

start_wqthread + 13

thread #14: tid = 0x13914, 0x00007fff8abd04de libsystem_kernel.dylib

mach_msg_trap + 10
    frame #0: 0x00007fff8abd04de libsystem_kernel.dylib

mach_msg_trap + 10
frame #1: 0x00007fff8abcf64f libsystem_kernel.dylib

mach_msg + 55
    frame #2: 0x00007fff8f946404 CoreFoundation

__CFRunLoopServiceMachPort + 212
frame #3: 0x00007fff8f9458cb CoreFoundation

__CFRunLoopRun + 1371
    frame #4: 0x00007fff8f945128 CoreFoundation

CFRunLoopRunSpecific + 296
frame #5: 0x00007fff897346bb AppKit

_NSEventThread + 137
    frame #6: 0x00007fff8c688268 libsystem_pthread.dylib

_pthread_body + 131
frame #7: 0x00007fff8c6881e5 libsystem_pthread.dylib

_pthread_start + 176
    frame #8: 0x00007fff8c68641d libsystem_pthread.dylib

thread_start + 13
(lldb) detach

=================================================================
Got a SIGSEGV while executing native code. This usually indicates
a fatal error in the mono runtime or one of the native libraries

used by your application.

Process 1333 detached
(lldb) quit

Please see the source code i attached.