「Unicode」

OpenClosePunctuationPair.cs

using System.Collections.Generic;
using System.Globalization;
using System.IO;
using System.Text;

class Program
{
    static readonly Encoding utf8 = Encoding.UTF8;

    static void Main()
    {
        using (var w = new StreamWriter("puncpair.txt", false, Encoding.UTF8))
        {
            foreach (var (o, c) in OpenClosePunctuationPair())
            {
                w.Write(o);
                w.Write(c);
            }
        }
    }

    private static IEnumerable<(char open, char close)> OpenClosePunctuationPair()
    {
        var open = '\0';
        for (int i = 0; i < 0x10000; i++)
        {
            var c = (char)i;
            var cat = char.GetUnicodeCategory(c);

            switch (cat)
            {
                case UnicodeCategory.InitialQuotePunctuation:
                case UnicodeCategory.OpenPunctuation:
                    open = c;
                    break;
                case UnicodeCategory.FinalQuotePunctuation:
                case UnicodeCategory.ClosePunctuation:
                    // 全角英数・半角カナ除外 (removes Full-witdh Alphanumerics and Half-width Katakana.)
                    var d = c.ToString().Normalize(NormalizationForm.FormKD)[0];
                    if (c != d) break;

                    // たいてい、ペアになってる括弧・引用符は隣り合ってるっぽい
                    // (In usual, open-close pairs are adjucent in Unicode code point.
                    if (i - open != 1) break;

                    yield return (open, c);
                    break;
            }
        }
    }
}