/// <summary>
/// Correlates the elements of two sequences based on matching keys. The default
/// equality comparer is used to compare keys.
/// </summary>
/// <typeparam name="TOuter">The type of the elements of the first sequence.</typeparam>
/// <typeparam name="TInner">The type of the elements of the second sequence.</typeparam>
/// <typeparam name="TKey">The type of the keys returned by the key selector functions.</typeparam>
/// <typeparam name="TResult">The type of the result elements.</typeparam>
/// <param name="outer">The first sequence to join.</param>
/// <param name="inner">The sequence to join to the first sequence.</param>
/// <param name="outerKeySelector">A function to extract the join key from each element of the first sequence.</param>
/// <param name="innerKeySelector">A function to extract the join key from each element of the second sequence.</param>
/// <param name="resultSelector">A function to create a result element from two combined elements.</param>
/// <returns>
/// An System.Collections.Generic.IEnumerable<T> that has elements of type TResult
/// that are obtained by performing a full outer join on two sequences.
/// </returns>
/// <example>
/// Example:
/// <code>
/// class TestClass
/// {
/// static int Main()
/// {
/// var strings1 = new string[] { "1", "2", "3", "4", "a" };
/// var strings2 = new string[] { "1", "2", "3", "16", "A" };
///
/// var lj = strings1.FullJoin(
/// strings2,
/// a => a,
/// b => b,
/// (a, b) => (a ?? "null") + "-" + (b ?? "null"))
/// .ToList();
/// }
/// }
/// </code>
/// </example>
public static IEnumerable <TResult> FullJoin <TOuter, TInner, TKey, TResult>(this IEnumerable <TOuter> outer,
IEnumerable <TInner> inner, Func <TOuter, TKey> outerKeySelector, Func <TInner, TKey> innerKeySelector,
Func <TOuter, TInner, TResult> resultSelector)
{
return(outer.FullJoin(inner, outerKeySelector, innerKeySelector, resultSelector, default(IEqualityComparer <TKey>)));
}
