Returning the differences between two enumerables

Question

I'm trying to determine the differences between two collections.

private ObservableCollection<SomeObject> _objectList = null;
private ObservableCollection<SomeObject> _cachedObjectList = null;

SomeObject implements IEquatable<SomeObject>

I'm using the following to determine if my two collections have any differences:

this._objectList.ToList().OrderBy(x => x.Id).SequenceEqual(this._cachedObjectList.ToList().OrderBy(x => x.Id));

• The _cachedObjectList collection will not change.
• You are able to Add, Remove, Or Modify an object in the _objectList collection.

How can i return a new list that contains any newly added, deleted, or otherwise modified object from the two collections.

Any help would be greatly appreciated!

IEquatable Implementation for SomeObject:

public class SomeObject : IEquatable<SomeObject>
{
        public int GetHashCode(SomeObject object)
        {
            return base.GetHashCode();
        }

        public bool Equals(SomeObject other)
        {
            bool result = true;


            if (Object.ReferenceEquals(other, null))
            {
                result = false;
            }

            //Check whether the compared objects reference the same data.
            if (Object.ReferenceEquals(this, other))
            {
                result = true;
            }
            else
            {
                // if the reference isn't the same, we can check the properties for equality
                if (!this.Id.Equals(other.Id))
                {
                    result = false;
                }

                if (!this.OtherList.OrderBy(x => x.Id).ToList().SequenceEqual(other.OtherList.OrderBy(x => x.Id).ToList()))
                {
                    result = false;
                }
            }

            return result;
        }
    }
}

EDIT: I only want the changes, if the _objectList contains a modified object, based on the IEquatable.Equals() then I'd like it returned. Otherwise, return new objects or removed objects in the list.

Answer 1

You would find the differences with

var newAndChanged = _objectList.Except(_cachedObjectList);
var removedAndChanged = _cachedObjectList.Except(_objectList);
var changed = newAndChanged.Concat(removedAndChanged);