public: IEnumerable<TSource> Union<TSource>( this IEnumerable<TSource> first, IEnumerable<TSource> second, IEqualityComparer<TSource> comparer );

public static IEnumerable<TSource> Union<TSource>( this IEnumerable<TSource> first, IEnumerable<TSource> second, IEqualityComparer<TSource> comparer );

Public static Function Union(Of TSource)( first As this IEnumerable<TSource>, second As IEnumerable<TSource>, comparer As IEqualityComparer<TSource> ) As IEnumerable<TSource>