title: Sharepoint via web service : checking if item exists in list
body: <p>Because Microsoft did not include a way to have unique constraints in sharepoint, this has to be done manually. </p>
  
  <p>I am inserting items into a sharepoint list via a web service method. </p>
  
  <p>How can I check if an existing list item already exists with the same field ID value?</p>
  
  <p>I've learnt I should be using wsLists.getListitems web service method, but its not exactly "user friendly". MSDN documentation is again not really great at explaining what should be an easy thing to do. </p>