/// <summary>
/// Converts the ISBN10 to ISBN13.
/// </summary>
/// <param name="isbn">The isbn.</param>
/// <returns></returns>
internal static string ConvertISBN10ToISBN13(string isbn)
{
// Add the prefix
isbn = Spec.PREFIX + isbn;
// Switch the checksums
var checksum = Spec.CalculateChecksum13(isbn);
isbn = isbn.Substring(0, isbn.Length - 1);
isbn += checksum;
return(isbn);
}