Hi All,
I am answering my self question. After a long investigation from the net i found below steps and now its working properly.
Step 1) Download and install the exact extension pack from internet for virtualbox to recognize the usb2.0 protocol. Because Azure Sphere devkit is running on usb2.0. Here is the web-site for download.
<LINK_TEXT text=“https://download.virtualbox.org/virtual … ox-extpack”>https://download.virtualbox.org/virtualbox/5.2.22/Oracle_VM_VirtualBox_Extension_Pack-5.2.22.vbox-extpack</LINK_TEXT>
Step 2) Install the extension pack as next-next-next steps.
[attachment=1]vbox_ext_pack_01.png[/attachment]
Step 3) Set the vm usb settings like below and boot the vm from virtualbox. After boot process wait near 2 minutes for self-installation of board drivers. Do nothing while it is installing the 3 com port drivers. Here is the below proper settings for vm.
[attachment=0]usb_settings_for_vm.png[/attachment]
regards. enjoy with your installed board.
kursat