title: MongoDB C# Driver - Update without Set/Replace
body: <p>I am communicating with a MongoDB database that is shared by another application that uses some fields that my application doesn't use or care about.</p>
  
  <p>Throughout my code, I use <code>Update.Replace</code> to update the object. The problem is that it replaces the entire document in the database with the one from my POCO object, causing the properties used by the other application to be removed.</p>
  
  <p>I could do <code>Update.Set</code>, but I would have to use that ALOT of times. <code>Update.Replace</code> is very convenient because it auto converts (by reflection) the POCO object to a <code>BsonDocument</code>.</p>
  
  <p>How do I auto-generate an <code>Update.Set</code> so that I don't have to call it for every member?</p>