Question

I have a string like:

BLOCK
    LIST1 Lorem ipsum dolor sit amet.
    LIST1 Lorem ipsum dolor sit amet.
    LIST1 Lorem ipsum dolor sit amet.
        LIST2 Lorem ipsum dolor sit amet.
        LIST2 Lorem ipsum dolor sit amet.
    LIST1 Lorem ipsum dolor sit amet.
BLOCK
    LIST1 Lorem ipsum dolor sit amet.
        LIST2 Lorem ipsum dolor sit amet.
            LIST3 Lorem ipsum dolor sit amet.
        LIST2 Lorem ipsum dolor sit amet.
    LIST1 Lorem ipsum dolor sit amet.
    LIST1 Lorem ipsum dolor sit amet.
    LIST1 Lorem ipsum dolor sit amet.

and want to transform it into

1. Lorem ipsum dolor sit amet.
    1. Lorem ipsum dolor sit amet.
    2. Lorem ipsum dolor sit amet.
    3. Lorem ipsum dolor sit amet.
        A. Lorem ipsum dolor sit amet.
        B. Lorem ipsum dolor sit amet.
    4. Lorem ipsum dolor sit amet.
2. Lorem ipsum dolor sit amet.
    1. Lorem ipsum dolor sit amet.
        A. Lorem ipsum dolor sit amet.
            a. Lorem ipsum dolor sit amet.
        B. Lorem ipsum dolor sit amet.
    2. Lorem ipsum dolor sit amet.
    3. Lorem ipsum dolor sit amet.
    4. Lorem ipsum dolor sit amet.

in another question, Numbering list elements with Regex in C#, dtb used single counter for every level, but I have a char array containing letters (A, B, C, D..) and want to use it for different levels.

Answer 1

Similar to Numbering list elements with Regex in C#

var input = "BLOCK\r\n    LIST1 Lorem ipsum dolor sit amet ...";

var levels = new List<string> { "BLOCK", "LIST1", "LIST2", "LIST3" };
var counter = levels.ToDictionary(level => level, level => 0);

// Replace each key word with incremented counter,
// while resetting deeper levels to 0.
var result = Regex.Replace(input, string.Join("|", levels), m =>
{
    for (int i = levels.IndexOf(m.Value) + 1; i < levels.Count; i++)
    {
        counter[levels[i]] = 0;
    }
    return GetLevelToken(m.Value, ++counter[m.Value]);
});

private static string GetLevelToken(string token, int index)
{
    switch (token)
    {
        case "BLOCK":
            return index.ToString() + ".";
        case "LIST1":
            return index.ToString() + ".";
        case "LIST2":
            return ((char)('A' + index - 1)).ToString();
    }
    return "";
}