string.split - by multiple character delimiter
To show both string.Split and Regex usage:
string input = "abc][rfd][5][,][.";
string[] parts1 = input.Split(new string[] { "][" }, StringSplitOptions.None);
string[] parts2 = Regex.Split(input, @"\]\[");
string tests = "abc][rfd][5][,][.";
string[] reslts = tests.Split(new char[] { ']', '[' }, StringSplitOptions.RemoveEmptyEntries);
Another option:
Replace the string delimiter with a single character, then split on that character.
string input = "abc][rfd][5][,][.";
string[] parts1 = input.Replace("][","-").Split('-');
Regex.Split("abc][rfd][5][,][.", @"\]\]");