Increment a string from numbers 0-9 to lowercase a-z to uppercase A-Z in C#

Question

I want to be able to have a string 6 characters long starting with \'000000\'. Then I want to increment it by one \'000001\' when I hit 9 I want to go to \'00000a\' when I g

Answer 1

This uses the IntToString supporting arbitrary bases from the question Quickest way to convert a base 10 number to any base in .NET?, but hardcoded to use your format (which is base 62).

private static readonly char[] baseChars = "0123456789abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ".ToCharArray();
private const long targetBase = 62;
private const long maxNum = 62L*62*62*62*62*62 - 1;
public static string NumberToString(long value)
{
    if (value > maxNum)
        throw new ArgumentException();
    char[] result = "000000".ToCharArray();

    int i = result.Length - 1;
    do
    {
        result[i--] = baseChars[value % targetBase];
        value /= targetBase;
    } 
    while (value > 0);

    return new string(result);
}