How to convert a windows form into Excel Sheet using VS2012

Question

I have some data in a dataGridView. I want to convert data on button click into a excel sheet.

I used the namespace

using Excel = Microsoft.Office.Interop.Excel;

 

but it gives an error at 'Office' . What should I do now? 

I am using VS2012 and SQL server 2008 with MS Office 2012.