/// <summary>
/// Performs a "union" of the two SerializableLists, where all the elements
/// in both SerializableLists are present. That is, the element is included if it is in either <c>a</c> or <c>b</c>.
/// Neither this SerializableList nor the input SerializableList are modified during the operation. The return value
/// is a <c>Clone()</c> of this SerializableList with the extra elements added in.
/// </summary>
/// <param name="a">A collection of elements.</param>
/// <returns>A new <c>SerializableList</c> containing the union of this <c>SerializableList</c> with the specified collection.
/// Neither of the input objects is modified by the union.</returns>
public virtual SerializableList <T> Union(SerializableList <T> a)
{
SerializableList <T> resultSerializableList = (SerializableList <T>) this.Clone();
if (a != null)
{
resultSerializableList.AddAll(a);
}
return(resultSerializableList);
}
