C#

static void Main(string[] args)
{
    foreach (string sperm in new PermutationEnumerator(2))
        Console.WriteLine(sperm);
    Console.ReadLine();
}

public class PermutationEnumerator : IEnumerator<string>, IEnumerable<string>
{
    int stringLength;
    char[] table;
    char[] chars;
    bool go = true;

    public PermutationEnumerator(int stringLength)
    {
        chars = new char[36];
        this.stringLength = stringLength;
        for (char c = '0'; c <= '9'; c++)
            chars[c - '0'] = c;
        for (char c = 'A'; c <= 'Z'; c++)
            chars[c - 'A' + 10] = c;
        Reset();
    }
    public string Current
    {
        get
        {
            if (table == null || !go) return null;
            return new string(table); 
        }
    }
    bool PlusOne(ref char c)
    {
        bool overflow = false;
        if (c >= '0' && c < '9')
            c = (char)(c + 1);
        else if (c == '9')
            c = 'A';
        else if (c >= 'A' && c < 'Z')
            c = (char)(c + 1);
        else
        {
            c = '0'; 
            overflow = true;
        }
        return overflow;
    }
    public void Dispose()
    {                
    }

    object System.Collections.IEnumerator.Current
    {
        get { return Current; }
    }

    public bool MoveNext()
    {
        if (table == null)
        {
            Init();
            return table.Length > 0;
        }
        int i;
        for (i = table.Length - 1; i >= 0; i--)
        {
            if (!PlusOne(ref table[i]))
                break;
        }
        go = i >= 0;
        return go;
    }

    public void Reset()
    {
        table = null;
    }
    void Init()
    {
        table = new char[stringLength];
        for (int i = 0; i < stringLength; i++)
        {
            table[i] = chars[0];
        }
    }
    void AddOne()
    {
        for (int i = table.Length - 1; i >= 0; i--)
        {
            if (!PlusOne(ref table[i]))
                break;
        }
    }

    public IEnumerator<string> GetEnumerator()
    {
        return this;
    }

    System.Collections.IEnumerator System.Collections.IEnumerable.GetEnumerator()
    {
        return GetEnumerator();
    }
}

MemberDotNetting wrote:

the connection does not work.

catch (OleDbException)
{
    ok = false;
}