save multiple row in gridview on click of single button outside of gridview

Hello Every One,

I am making a project in c#. In a gridview i have two three columns ID, status, comment.
for status i have used two radio button in gridview column. so in my gridview's every row i have one radio button in status column and one textbox in comment column.
fo save changes i use a button outside of the gridview. for update the changes in database.
I want that when user click on save hanges button then update query should be execute only for those ID in which comment or status has been changed. Means i don't want to execute update query for every row of gridview.
so i am not understand taht how i will find that in which row textbox value is changed or not.

please giveme any idea.

thanks in advance

Tags: ASP.NET