Macbook Air 13 inch (256 GB/ 8 GB/ i5) along with Windows (Using BootCamp) I am completely new to the Mac and I am planning to buy MacAir (256 GB/ 8 GB/ i5) model and want to use Windows 7 along with it using BootCamp. I have no problem with MacOSX but need to use Windows (Visual Studio 2013 specially) because of my job demand (.Net Developer). I want to use Mac mainly because of Battery Life and Performance. My question is that Can I experience the same when I will use Windows? 

Apart from that I also heard that Windows reduce the battery life. So Does it mean that my battery life will be affected even when I will use MacOSX. Thanks in Advance
If you are truly dual booting (using Boot Camp) you will find your battery life better on OS X than on Windows. However, when you boot into OS X, you won't suffer any ill effects from having a separate Windows partition sitting idle. 

If you opt to run Windows in a Virtual Machine (using, for example, Parallels Desktop, VMWare Fusion, or Virtualbox), you will notice a significant decrease in battery life because you'll be running both "machines" (OS X and Windows) at one time.