Get datagrid textbox value

I have bound datagrid with edit,update events. I am able to extract textbox values of datagrid in edit event but in the update event, its returning null textbox value. I want to get the value of textbox that is dynamically generated by the datagrid in update event.

TextBox txtbox = new TextBox();
txtbox = (TextBox)e.Item.FindControl(e.Item.Cells[1].Controls[0].ID);

the above code returns null value for txtbox.Text.

I also tried extracting vaues using these lines of code, but still returns null

TextBox txtbox = new TextBox();
txtbox = (TextBox)e.Item.Cells[1].Controls[0];
string lastname = txtbox.text

kanchangorak