I'm not quite sure i follow 100% but you could have a drop down that is populated from the database, Select the item in this drop down, Enter the details in to your textboxes and have a button to activate the update.
In steps
Get your data into a local list.
Populate the drop down using this list.
You now still have your local list with the appropriate data.
Get the user to select an item from the drop down.
Use the drop downs selected index to get the item from the list.
Change the values within this item and commit to the database
I would have thought it would be far easier using the appropriate control for displaying the information such as a listview or datagrid
List<String> objInformationList = new List<String>();
objInformationList = "Your database query function";
foreach(String objCurrentString in objInformationList){
// Create your text box
// Set your text within your textbox
// Add the text box to the screen or a table structure
}
I personally would be doing this another way