How to get Repeater Row Item Index inside TextBox TextChanged event in ASP.Net

Hi friends, I need your help, I have a repeater control. show my products. in the quantity column I have a textbox that fills from database, the problem is when I want to update the quantity from the textbox, I have no idea how to get the id of the row repeater and the value of the textbox to update the record. try using the method OnTextChanged. or maybe Jquery?. if they could give me an idea to start. would be great for me, thanks.