Saya menulis kelas khusus untuk melakukan ini. Ini diinisialisasi dengan bagian "basis" (default ke stempel waktu akurat-menit) dan setelah itu menambahkan huruf untuk membuat nama-nama unik. Jadi, jika cap pertama yang dihasilkan adalah 1907101215a, yang kedua adalah 1907101215b, maka 1907101215c, dan lain-lain.
Jika saya membutuhkan lebih dari 25 perangko unik maka saya menggunakan unary 'z's untuk menghitung 25's. Jadi, begini 1907101215y, 1907101215za, 1907101215zb, ... 1907101215zy, 1907101215zza, 1907101215zzb, dan sebagainya. Ini menjamin bahwa prangko akan selalu disortir secara alfanumerik sesuai urutan pembuatannya (selama karakter berikutnya setelah cap bukan surat).
Ini bukan thread-safe, tidak secara otomatis memperbarui waktu, dan cepat menggembung jika Anda membutuhkan ratusan prangko, tetapi saya merasa cukup untuk kebutuhan saya.
/// <summary>
/// Class for generating unique stamps (for filenames, etc.)
/// </summary>
/// <remarks>
/// Each time ToString() is called, a unique stamp is generated.
/// Stamps are guaranteed to sort alphanumerically in order of generation.
/// </remarks>
public class StampGenerator
{
/// <summary>
/// All the characters which could be the last character in the stamp.
/// </summary>
private static readonly char[] _trailingChars =
{
'a', 'b', 'c', 'd', 'e', 'f', 'g', 'h', 'i', 'j',
'k', 'l', 'm', 'n', 'o', 'p', 'q', 'r', 's', 't',
'u', 'v', 'w', 'x', 'y'
};
/// <summary>
/// How many valid trailing characters there are.
/// </summary>
/// <remarks>Should always equal _trailingChars.Length</remarks>
public const int TRAILING_RANGE = 25;
/// <summary>
/// Maximum length of the stamp. Hard-coded for laziness.
/// </summary>
public const int MAX_LENGTH_STAMP = 28;
/// <summary>
/// Base portion of the stamp. Will be constant between calls.
/// </summary>
/// <remarks>
/// This is intended to uniquely distinguish between instances.
/// Default behavior is to generate a minute-accurate timestamp.
/// </remarks>
public string StampBase { get; }
/// <summary>
/// Number of times this instance has been called.
/// </summary>
public int CalledTimes { get; private set; }
/// <summary>
/// Maximum number of stamps that can be generated with a given base.
/// </summary>
public int MaxCalls { get; }
/// <summary>
/// Number of stamps remaining for this instance.
/// </summary>
public int RemainingCalls { get { return MaxCalls - CalledTimes; } }
/// <summary>
/// Instantiate a StampGenerator with a specific base.
/// </summary>
/// <param name="stampBase">Base of stamp.</param>
/// <param name="calledTimes">
/// Number of times this base has already been used.
/// </param>
public StampGenerator(string stampBase, int calledTimes = 0)
{
if (stampBase == null)
{
throw new ArgumentNullException("stampBase");
}
else if (Regex.IsMatch(stampBase, "[^a-zA-Z_0-9 \\-]"))
{
throw new ArgumentException("Invalid characters in Stamp Base.",
"stampBase");
}
else if (stampBase.Length >= MAX_LENGTH_STAMP - 1)
{
throw new ArgumentException(
string.Format("Stamp Base too long. (Length {0} out of {1})",
stampBase.Length, MAX_LENGTH_STAMP - 1), "stampBase");
}
else if (calledTimes < 0)
{
throw new ArgumentOutOfRangeException(
"calledTimes", calledTimes, "calledTimes cannot be negative.");
}
else
{
int maxCalls = TRAILING_RANGE * (MAX_LENGTH_STAMP - stampBase.Length);
if (calledTimes >= maxCalls)
{
throw new ArgumentOutOfRangeException(
"calledTimes", calledTimes, string.Format(
"Called Times too large; max for stem of length {0} is {1}.",
stampBase.Length, maxCalls));
}
else
{
StampBase = stampBase;
CalledTimes = calledTimes;
MaxCalls = maxCalls;
}
}
}
/// <summary>
/// Instantiate a StampGenerator with default base string based on time.
/// </summary>
public StampGenerator() : this(DateTime.Now.ToString("yMMddHHmm")) { }
/// <summary>
/// Generate a unique stamp.
/// </summary>
/// <remarks>
/// Stamp values are orered like this:
/// a, b, ... x, y, za, zb, ... zx, zy, zza, zzb, ...
/// </remarks>
/// <returns>A unique stamp.</returns>
public override string ToString()
{
int zCount = CalledTimes / TRAILING_RANGE;
int trailing = CalledTimes % TRAILING_RANGE;
int length = StampBase.Length + zCount + 1;
if (length > MAX_LENGTH_STAMP)
{
throw new InvalidOperationException(
"Stamp length overflown! Cannot generate new stamps.");
}
else
{
CalledTimes = CalledTimes + 1;
var builder = new StringBuilder(StampBase, length);
builder.Append('z', zCount);
builder.Append(_trailingChars[trailing]);
return builder.ToString();
}
}
}