title: SharePoint : Check if item exists in a list, minimum overhead
body: <p>How can I check if a list contains an item... really only interested in checking 1 field, not every single field in the list. </p>
  
  <p>How can this be done in the most efficient way, creating a SPListItemCollection and itterating through this to check for unique values is really going to flatline the cpu usage... Surely there must be a way to do this without itterating through every item in the list?</p>