AlphanumericCheckDigitAlgorithm Class
Definition
Represents the abstract base class from which single-character check-digit algorithms that operate on a wider input
alphabet, or whose check character may be the sentinel 'X', derive.
public abstract class AlphanumericCheckDigitAlgorithm : CheckValueAlgorithm- Inheritance
-
AlphanumericCheckDigitAlgorithm
- Derived
- Inherited Members
- Extension Methods
Examples
// Use a concrete derivative through the abstract surface - ISIN accepts a mix of
// ASCII letters (the country code) and digits.
AlphanumericCheckDigitAlgorithm algo = new Isin();
algo.Append("US037833100"); // Apple Inc.
char check = algo.GetCurrentCheckDigit(); // '5'
// Inspect the declared alphabets for input validation upstream.
CheckDigitInputAlphabet inputs = algo.InputAlphabet;
CheckDigitOutputAlphabet outputs = algo.OutputAlphabet;Remarks
Parallel in design to CheckDigitAlgorithm, this base relaxes two constraints: the input may be any
subset of ASCII declared by InputAlphabet (decimal digits, or decimal digits and uppercase Latin
letters), and the emitted check character may be any value of OutputAlphabet - notably including the
'X' sentinel used by ISBN-10 and ISO 7064 MOD 11-2 to represent the check value ten.
Like the rest of this family, the type is intentionally separate from the byte-stream oriented NonCryptographicHashAlgorithm and does not derive from it. A non-cryptographic hash produces a fixed-length opaque byte digest over arbitrary input; a check character performs error detection over a constrained ASCII text alphabet and emits a single char. The families are kept distinct by design rather than unified under one base type.
The streaming surface - Append(ReadOnlySpan<char>), Reset(), and GetCurrentCheckDigit() - will nonetheless feel familiar to anyone who has used a hash algorithm: input is accumulated, the computation can be restarted, and reading the current check character is non-destructive and idempotent. That resemblance is incidental convenience, not a shared contract. Concrete implementations document their empty-body behavior.
Instances are not thread-safe. Each thread that needs a running check should construct its own instance.
important
Check-digit algorithms are error-detection primitives, not cryptographic functions. They must not be used for password hashing, digital signatures, or integrity validation in security-sensitive applications.
Constructors
AlphanumericCheckDigitAlgorithm()
Initializes a new instance of the AlphanumericCheckDigitAlgorithm class.
protected AlphanumericCheckDigitAlgorithm()Properties
InputAlphabet
Gets the subset of ASCII from which this algorithm accepts body characters.
public abstract CheckDigitInputAlphabet InputAlphabet { get; }Property Value
- CheckDigitInputAlphabet
The declared input alphabet.
OutputAlphabet
Gets the subset of ASCII from which this algorithm may emit its check character.
public abstract CheckDigitOutputAlphabet OutputAlphabet { get; }Property Value
- CheckDigitOutputAlphabet
The declared output alphabet.
Methods
GetCurrentCheckDigit()
Returns the check character computed for the body absorbed since the last Reset() (or since construction).
public abstract char GetCurrentCheckDigit()Returns
- char
The check character as an ASCII character drawn from OutputAlphabet.
Remarks
This call is non-destructive; the running state is unaffected and the method may be invoked any number of times with identical results between appends.
GetCurrentCheckValue()
Returns the check value computed for the body absorbed since the last Reset() (or since construction) as a newly allocated string.
public override sealed string GetCurrentCheckValue()Returns
- string
A string of length CheckLength containing the check value.
Remarks
This call is non-destructive; the running state is unaffected and the method may be invoked any number of times
with identical results between appends. The single-character branches also expose the result as a
char via GetCurrentCheckDigit(), which avoids the string allocation.
Applies to
| Product | Versions |
|---|---|
| .NET | 8, 10 |