Saving Data In A DataTable To The Physical Database?

I've been looking at this problem for a while and can't see what I'm doing wrong. I need an extra set of eyes. The business problem that I am trying to solve is the following:I have a table that contains a list of auction items that are displayed in a datagridview. I have another table that has a list of bidders. At the end of the auction I need to update the Winners table with the bidder number and item number of the auction item. To do this, I display all of the auction items and then let the user enter the bidder number and winning bid amount in the datagridview. When finished, the user clicks on Save and the information is pulled from the datagridview and saved in the Winners table.

I have a datagridview (AuctionItemsDataGridView) that uses the auctionitems table from my database as its source. I add the BidderNo, WinningBid and BidderName columns to the datagridview when the form is loaded. There are 3 types of auction items so I prompt the user for the type of auction items to display using a combotextbox (CategoryComboBox). When an auction category is chosen, I load the auction items for that code into the datagridview. I then load the winners from the winners table into a WinnersDataTable (WinnersDT). For each item in the datagridview, I check if there is a corresponding item in the Winners Table. If there is then I populate the BidderNo and WinningBid columns of the datagridview (I also populate the BidderName). So far all of this works. The problem is when I make a change to the datagridview.If I enter a bidder number and winnng bid amount the data is not being saved to the physical database table. To save the data I perform the following:

For each item in the datagridview, check if a Bidder Number is entered. If a bidder has been entered, I check to see if there is a corresponding winners record in the WinnersDataTable for the current item. If yes, I enter the bidder number and winnng bid amount in the table. If there isn't a record, I add a new one. After looking at each item I call the Update method on the WinnersDataTable.

Public Class Winners
Dim BidderDT As DataTable
Dim WinnersDT As DataTable
Dim pageLoading As Boolean

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