/// <summary>
/// Creates a new instance of <see cref="CollectionModification"/>.
/// </summary>
/// <param name="existingObjects">The current collection of objects.</param>
/// <param name="updatedObjects">The collection containing objects that were imported
/// and thus could contain updates for the existing objects.</param>
/// <param name="equalityComparer">The comparer to test whether elements in
/// <paramref name="existingObjects"/> have a matching element in
/// <paramref name="updatedObjects"/>.</param>
/// <exception cref="ArgumentNullException">Thrown if any parameter is <c>null</c>.</exception>
/// <exception cref="ArgumentException">Thrown when <paramref name="existingObjects"/>
/// or <paramref name="updatedObjects"/> contains a <c>null</c> element.</exception>
public CollectionModification(IEnumerable <TTargetData> existingObjects,
IEnumerable <TTargetData> updatedObjects,
IEqualityComparer <TTargetData> equalityComparer)
{
if (existingObjects == null)
{
throw new ArgumentNullException(nameof(existingObjects));
}
if (updatedObjects == null)
{
throw new ArgumentNullException(nameof(updatedObjects));
}
if (equalityComparer == null)
{
throw new ArgumentNullException(nameof(equalityComparer));
}
if (existingObjects.Contains(null))
{
throw new ArgumentException(@"Cannot determine modifications from a collection which contain null.", nameof(existingObjects));
}
if (updatedObjects.Contains(null))
{
throw new ArgumentException(@"Cannot determine modifications with a collection which contain null.", nameof(updatedObjects));
}
TTargetData[] existingArray = existingObjects.ToArray();
var index = 0;
foreach (TTargetData importedObject in updatedObjects)
{
int existingObjectIndex = FindIndex(existingArray, importedObject, equalityComparer);
if (existingObjectIndex > -1)
{
ObjectsToBeUpdated.Add(index, existingArray[existingObjectIndex]);
existingArray[existingObjectIndex] = null;
}
else
{
ObjectsToBeAdded.Add(index, importedObject);
}
index++;
}
ObjectsToBeRemoved = existingArray.Where(e => e != null);
}
/// <summary>
/// Finds out whether there was a difference between the existing and the imported
/// object collections.
/// </summary>
/// <returns><c>true</c> if there were any updates, <c>false</c> otherwise.</returns>
public bool HasUpdates()
{
return(ObjectsToBeRemoved.Any() || ObjectsToBeAdded.Any() || ObjectsToBeUpdated.Any());
}