Разница между шаблоном проактора и синхронной моделью в веб-сервере

/// <summary>
/// Validates a GTIN (UPC/EAN) using the terminating check digit
/// </summary>
/// <param name="code">the string representing the GTIN</param>
/// <returns>True if the check digit matches, false if the code is not 
/// parsable as a GTIN or the check digit does not match</returns>
public static bool IsValidGtin(string code)
{
    if (string.IsNullOrWhiteSpace(code))
        return false;
    if (code.Length != 8 && code.Length != 12 && code.Length != 13 
        && code.Length != 14)
        // wrong number of digits
        return false;

    int sum = 0;
    for (int i = 0; i < code.Length - 1 /* do not include check char */; i++)
    {
        if (!char.IsNumber(code[i]))
            return false;

        var cchari = (int)char.GetNumericValue(code[i]);
        // even (from the right) characters get multiplied by 3
        // add the length to align right
        if ((code.Length + i) % 2 == 0)
            sum += cchari * 3;
        else
            sum += cchari;
    }

    // validate check char
    char checkChar = code[code.Length - 1];
    if (!char.IsNumber(checkChar))
        return false;

    int checkChari = (int)char.GetNumericValue(checkChar);
    return checkChari == (10 - (sum % 10)) % 10;
}

Тестовые случаи:

    [TestMethod()]
    public void IsValidGtinTest_Valid()
    {
        string[] valid = new[] {
            "085126880552",
            "0085126880552",
            "00085126880552",
            "0786936226355",
            "0719852136552"
        };
        foreach (var upc in valid)
            Assert.IsTrue(IdentifierUtilities.IsValidGtin(upc), upc);
    }

    [TestMethod()]
    public void IsValidGtinTest_Invalid()
    {
        string[] invalid = new[] {
            "0058126880552",
            "58126880552",
            "0786936223655",
            "0719853136552",
            "",
            "00",
            null,
            "123456789123456789123456789",
            "1111111111111"
        };
        foreach (var upc in invalid)
            Assert.IsFalse(IdentifierUtilities.IsValidGtin(upc), upc);
    }