/// <summary>
/// Projects each element of a sequence into a new form.
/// </summary>
/// <typeparam name="TSource">The type of the elements of source.</typeparam>
/// <typeparam name="TResult">The type of the value returned by selector.</typeparam>
/// <param name="source">A sequence of values to invoke a transform function on.</param>
/// <param name="selector">A transform function to apply to each element.</param>
/// <returns>An <see cref="IEnumerable<T>"/> whose elements are the result of invoking the transform function on each element of source..</returns>
/// <exception cref="ArgumentNullException">The <paramref name="source"/> or <paramref name="selector"/> argument is null.</exception>
internal static IEnumerable <TResult> Select <TSource, TResult>(this IEnumerable <TSource> source, Func <TSource, TResult> selector)
{
if (null == source)
{
throw new ArgumentNullException("source");
}
else if (null == selector)
{
throw new ArgumentNullException("selector");
}
// Project each item in a separate method or null checks above are compiled away.
return(ExtensionMethods.SelectIterator(source, selector));
}
/// <summary>
/// Reeturns the sum of the field selected from each item in the source enumerable.
/// </summary>
/// <typeparam name="TSource">The type of the elements of source.</typeparam>
/// <param name="source">A sequence of values from which fields are selected to sum.</param>
/// <param name="selector">A transform function to apply to each element to get the field to sum.</param>
/// <returns>The sum of the field selected from each item in the source enumerable.</returns>
/// <exception cref="ArgumentNullException">The <paramref name="source"/> or <paramref name="selector"/> argument is null.</exception>
internal static long Sum <TSource>(this IEnumerable <TSource> source, Func <TSource, long> selector)
{
if (null == source)
{
throw new ArgumentNullException("source");
}
else if (null == selector)
{
throw new ArgumentNullException("selector");
}
var sum = 0L;
foreach (long i in ExtensionMethods.SelectIterator(source, selector))
{
sum += i;
}
return(sum);
}
