Question

How may I correctly assign textboxes, dropdownlists & labels to appropriate fields, on successful retrieval of records via a SQL statement? I have 4 tables & therefore, the assigned data don’t match the controls. (VS2008)

I have the following:

myCmd.CommandText = "SELECT pc.product_category_id, pc.product_category_name, pi.product_image_id, pi.product_image_filename, qr.qrcode_id, qr.qrcode_image_filename, p.product_author FROM Product AS p INNER JOIN ProductCategory AS pc ON p.product_category_id = pc.product_category_id INNER JOIN ProductImage AS pi ON p.product_image_id = pi.product_image_id INNER JOIN  QRCode AS qr ON p.qrcode_id = qr.qrcode_id WHERE p.product_id = '" & DropDownList2.Text & "'"

myCmd.Parameters.Add(New SqlParameter("@product_id", (DropDownList2.Text)))
myConn.Open()
'run the query and obtain a reader to get the results 
dtrReader = myCmd.ExecuteReader()

'check if there are results
If (dtrReader.Read()) Then
   'populate the values of the controls
   lblProductID2.Text = dtrReader(0)
   txtProductName2.Text = dtrReader(4)
   txtProductTitle2.Text = dtrReader(7)
   txtProductDescription2.Text = dtrReader(8)
   txtProductAuthor2.Text = dtrReader(12)

Answer 1

There are at least two ways to solve this:

1) Explicitly use the names of the columns when retrieving from datareader:

lblProductID2.Text = dtrReader("product_category_id")
' etc

2) Cycle through each of the fields in the reader and use a case statement to assign values

For nI As Integer = 0 To dtrReader.FieldCount - 1
   Select Case dtrReader.GetName(nI).ToLower()
      Case "product_category_id"
         If Not dtrReader.IsDBNull(nI) Then
             lblProductID2.Text = dtrReader.GetString(nI)
         Else
             lblProductID2.Text = String.Empty
         End If

      ' etc

   End Select
Next

Number 2 is probably slightly better because it makes it easier to test for DBNull values in the returned data: