Post vs Put vs Patch in Web API

 Debates rages on and on. Why, when and how.
 My 2 cents:

1. POST- create if you don't know resource location, but leaving it to the server to determine it and send back location of new resource to you in the header.
2. PUT - hm, it should really be called replace. It should either create resource on specified url (by client!) or completely update it, no partial updates here.
3. PATCH - intended for partial updates, not really available yet.
4. POST - update - tricky one. Since we don't have PATCH yet that's the only alternative for partial updates as of now.

So something like this for POST:

// POST: api/Items
[ResponseType(typeof(BudgetItem))]
public IHttpActionResult Post(BudgetItem item)
 {
   if (ModelState.IsValid)
     {
        _itemRepository.CreateItem(item);
        return CreatedAtRoute("DefaultApi", new { id = item.Id }, item);
     }
   else
      {
      return BadRequest(ModelState);
      }
  }

And for PUT:

// PUT: api/Items/5
public IHttpActionResult Put(int id, BudgetItem item)
  {
     if (!ModelState.IsValid)
       {
           return BadRequest(ModelState);
        }
     BudgetItem oldItem = _itemRepository.GetItem(id);
     if (oldItem == null)
        {
           _itemRepository.CreateItem(item);
           return CreatedAtRoute("DefaultApi", new { id = item.Id }, item);
        }
      else
       {
          _itemRepository.UpdateItem(item);
          return Ok(item);
       }
   }