Compare two lists of object for new, changed, updated on a specific property

Question

I\'ve been trying and failing for a while to find a solution to compare to lists of objects based on a property of the objects. I\'ve read other similar solutions but they w

Answer 1

One simple approach would be to override the == operator in yourAccomodationImageModel as such:

public static override bool operator ==(AccommodationImageModel a, AccommodationImageModel b)
{
    return a.Id == b.Id;
}

Then when comparing just check the master list against the comparer list and remove those in the master list that don't have an identical object in the comparer list:

List rem = new List;
List newobj = new List;
foreach(AccomodationImageModel a in compareList) {
          if(a.Id == 0) { // id == 0 => new item
                 newobj.Add(a); // add new item later
          } else {
                 // check those existing items as to whether they need to be updated or removed
                 bool match = false;
                 foreach(AccomodationImageModel b in masterList) {
                      if(a == b) match = true; // match found
                 }
                 if(!match) rem.Add(a); else Update(a); // will be removed or updated
          }
}
// now remove unmatched items
foreach(AccomodationImageModel a in rem) { masterList.Remove(a); }
foreach(AccomodationImageModel a in newobj) { AddNew(a); }

Note Update(AccomodationImageModel a) is your method to update a certain item and AddNew(AccomodationImageModel a) is your method of insterting a new item in the master list.

Also as you may have noteiced removing from and inserting to the master list should be done after you have looped the master list!