title: C# Only allowing qr code to be scanned once
body: <p>We use QR codes on our products. Each QR code is virtually identical except for a unique serial number. </p>
  
  <p>I'm writing a C# Win Form program for building product KITS. They then scan off each product within that KIT to complete the Order. Some KITS contain multiples of the same product. <strong>I want to prevent the user from simply scanning the same QR code for a product with multiples in a KIT.</strong> </p>
  
  <p>I will be creating a database for this Win App to store which qr codes have been scanned off the total amount needed for the KIT. </p>
  
  <p>To ensure that the same QR code isn't scanned, would I be correct in assuming I'd simply need to run a check against the serial numbers previously scanned in the database? If so, how is the most efficient way to do this?</p>
  
  <p>Thanks</p>