此代碼驗證ISBN是否有效。對於九位輸入,我想通過計算並附加校驗碼來形成有效的ISBN。對於少於九位數的輸入,我希望它返回錯誤消息「請輸入正確的數字」。我應該怎麼做呢?Isbn生成校驗位
public class isbn
{ //attributes
private string isbnNum;
//method
public string GetIsbn()
{
return this.isbnNum;
}
//constructor
public isbn()
{
Console.Write("Enter Your ISBN Number: ");
this.isbnNum = Console.ReadLine();
}//end default constructor
//method
public string displayISBN()
{
return this.GetIsbn();
}
public static void Main(string[] args)
{
//create a new instance of the ISBN/book class
isbn myFavoriteBook = new isbn();
//contains the method for checking validity
bool isValid = CheckDigit.CheckIsbn(myFavoriteBook.GetIsbn());
//print out the results of the validity.
Console.WriteLine(string.Format("Your book {0} a valid ISBN",
isValid ? "has" : "doesn't have"));
Console.ReadLine();
}
public static class CheckDigit
{ // attributes
public static string NormalizeIsbn(string isbn)
{
return isbn.Replace("-", "").Replace(" ", "");
}
public static bool CheckIsbn(string isbn) // formula to check ISBN's validity
{
if (isbn == null)
return false;
isbn = NormalizeIsbn (isbn);
if (isbn.Length != 10)
return false;
int result;
for (int i = 0; i < 9; i++)
if (!int.TryParse(isbn[i].ToString(), out result))
return false;
int sum = 0;
for (int i = 0; i < 9; i++)
sum += (i + 1) * int.Parse(isbn[i].ToString());
int remainder = sum % 11;
if (remainder == 10)
return isbn[9] == 'X';
else
return isbn[9] == (char)('0' + remainder);
}
是這功課嗎? – dtb 2010-09-02 20:05:37
不是它是一本書的練習 – 2010-09-02 20:31:39