title: The proper way to write a SharePoint User to a User Field in a SharePoint list
body: <p>I'm writing a user to a SharePoint list.</p>
  
  <p>I've read that the SharePoint User field has a string like this inside of it:
  <code>userId;#userLoginName</code></p>
  
  <p>I've tried formatting in the same way when writing to a User field, for example when I write this string it works:
  <code>9;#i:0#.f|membership|ectropy@example.org</code></p>
  
  <p>But what is strange (to me at least) is that <code>9;#</code> seems to work or even <code>9</code>. Even if I don't pass the <code>userLoginName</code> info at all, the <code>loginId</code> seems to be enough for it to recognize which User I'm talking about.</p>
  
  <p>This seems to imply that when writing to the SharePoint User field, you only need the id, and the <code>userLoginName</code>, or, indeed, everything after the <code>loginId</code> is irrelevant.</p>
  
  <p>Am I correct in my reasoning here? Or perhaps there's unexpected consequences if I leave off the userLoginName information?</p>