How to make insert delete update select in ASP.Net GridView

Hi

i have a student data , when i put the student id in textbox , it show thw students mark in gridview like

1st semester marks in first row , 2nd semester marks in second row ,etc

and i want insert 3rd semester marks , 4th semester marks for the particular student , and also , delete , update in gridview

How can i ,pls help me?

Thanks in advance