public static bool IsValidIsnb10Checksum(String isbn)
{
if (isbn == null)
{
return(false);
}
// Remove leading 'ISBN' String
isbn = RemoveIsbn10(isbn);
// Check, if ISBN is digits only and of length 10
if (!ValidatorHelpers.IsDigitsOnly(isbn) || isbn.Length != 10)
{
return(false);
}
// Calculate checksum
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));
}
}
public static bool IsValidUpc(string upc)
{
try
{
return(ValidatorHelpers.IsValidGtin(upc));
}
catch
{
return(false);
}
}
public static bool IsValidEanChecksum(String ean)
{
try
{
return(ValidatorHelpers.IsStandardChecksumValid(ean));
}
catch
{
return(false);
}
}
public static bool IsValidIsbn13Checksum(String isbn)
{
isbn = RemoveIsbn13(isbn);
if (!ValidatorHelpers.IsDigitsOnly(isbn) || isbn.Length != 13)
{
return(false);
}
var weight = 1;
var sum = 0;
for (int i = 0; i < isbn.Length - 1; i++)
{
sum += int.Parse(isbn[i].ToString()) * weight;
weight = (weight + 2) % 4;
}
var remainder = (10 - (sum % 10)) % 10;
return(isbn[isbn.Length - 1] == (char)('0' + remainder));
}
