in windows 8 wifi connection not showing and there is no option to on/off wifi and wifi button also does not work

Hi,

Check with the System Maker if an on-board WiFI device and the
actual device maker if using an add-on device. Either the device is
off or it has failed. You may want to check with a local computer
shop (one that does its own in-shop service on that make).

Note using Win Key + X and Win Key + W (to get to Control Panel, Run,
and Settings as needed). Win Key + D calls the desktop and the using
Win Key toggles Desktop and Start Screen.

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Control Panel - Network and Sharing Center - Troubleshoot Problems

References to Vista also apply to Windows 7 and Windows 8.

Once the device is ON try actually updating your driver : 

Control Panel - Network - write down make and model of Wifi - double click
on it - driver's tab - write down version - click Update Driver (may not do
anything as MS is far behind certifying drivers). Then Right Click on Wifi
Device and UNINSTALL - Reboot - this will refresh the driver stack.

Manually look at manufacturer's sites for drivers - and Device Maker's sites.
http://pcsupport.about.com/od/driverssupport/ht/driverdlmfgr.htm

Microsoft - Windows 8 - How do I fix network adapter problems? (Be sure to see
this section ->Update the network adapter driver.)
http://windows.microsoft.com/en-US/windows-8/fix-network-adapter-problems

Microsoft - Windows 8 - Hardware and Drivers
http://windows.microsoft.com/en-US/windows/hardware-drivers-help#hardware-drivers-help=windows-8

Microsoft - Windows 8 - Why isn't Windows finding my device?
http://windows.microsoft.com/en-US/windows-8/why-isnt-windows-finding-device

Microsoft - Windows 8 - What if a device isn't installed properly
http://windows.microsoft.com/en-US/windows-8/what-device-isnt-installed-properly

Download - SAVE - go to where you put it - Right Click - RUN AS ADMIN.

You can download several at once however reboot after you install each one.

After looking at the System Maker's you can check Device Maker's for even
newer versions. (The ones from System maker become your fallbacks).

Repeat above for network card (NIC) and is a good time to get other updated
drivers as Windows 8 loves updated drivers.

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And :

TechingItEasy - How to join a Wi-Fi Network in Windows 8 by MVP Andre Da Costa
http://techingiteasy.wordpress.com/2012/06/09/how-to-join-a-wi-fi-network-in-windows-8/

Microsoft - Windows 8 - Web & Networking
http://windows.microsoft.com/en-US/windows/web-networking-help#v1h=win8tab1&v2h=win7tab1&v3h=winvistatab1&v4h=winxptab1&web-networking-help=windows-8

Microsoft - Windows 8 - Wi-Fi & Networking
http://windows.microsoft.com/en-US/windows-8/wifi-networking#1TC=t1

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Microsoft - Windows 7 - Why is my Internet connection so slow? (applies to Windows 8)
http://windows.microsoft.com/en-US/windows7/Why-is-my-Internet-connection-so-slow

Microsoft - Windows 8 - Wired and wireless network problems in Windows
http://windows.microsoft.com/en-US/windows/network-connection-problem-help#network-problems=windows-8&v1h=win8tab1&v2h=win7tab1&v3h=winvistatab1&v4h=winxptab1

Hope this helps.

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Rob Brown - Microsoft MVP <- profile - Windows Expert - Consumer : Bicycle <- Mark Twain said it right!