/// <summary>Inserts the elements of a collection into the list at the specified index.</summary>
/// <param name="index">The zero-based index at which the new elements should be inserted.</param>
/// <param name="elements">
/// The collection whose elements should be inserted into the list.
/// The collection itself cannot be null, but it can contain elements that are null,
/// if type <typeparamref name="T" /> is a reference type.
/// </param>
/// <exception cref="ArgumentOutOfRangeException">index is less than 0 -or- index is greater than Count.</exception>
public void InsertRange(int index, [NotNull] IEnumerable <T> elements)
{
Check.NotNull(elements)
.InRange(index, 0, Count, "index is less than 0 -or- index is greater than Count.",
nameof(index));
// First call the pre-event if needed, enumerating sequence in process:
var success = true;
IEnumerable <T> fixedElements = null;
var beforeRangeAdditionHandler = Volatile.Read(ref BeforeRangeAddition);
if (EventsEnabled && (beforeRangeAdditionHandler != null))
{
// ReSharper disable PossibleMultipleEnumeration
fixedElements = elements as ICollection <T> ?? elements.ToArray();
success = beforeRangeAdditionHandler(this, index, (ICollection <T>)fixedElements);
}
if (success)
{
// Enumerated sequence will be null if pre-event was not called, since no enumeration was done.
if (fixedElements == null)
{
fixedElements = elements;
}
// ReSharper enable PossibleMultipleEnumeration
var countBefore = Count;
_list.InsertRange(index, fixedElements);
var addedTotal = Count - countBefore;
if (EventsEnabled && (addedTotal > 0))
{
RangeAdded.Call(this, index, addedTotal);
}
}
}
