.NET Regular Expression allow 3 repeated characters

Question

I'm trying to create a .NET regular expression with the following criteria below but no go. All I have is the regular expression below. Any help would be greatly appreciated!!

1. 8-15 characters (alpha or numeric and not case sensitive)
2. maximum of 3 repeated characters or numbers allowed
3. No special characters or symbols

This is what I've got:

^(?=.*[0-9].*)(?=.*[A-Za-z].*)([0-9A-Za-z]\1{3}){8,15}$

Answer 1

This regex will work

^(?=.{8,15}$)(?!.*?(.)\1{3})[A-Za-z0-9]+$

Regex Demo

Regex Breakdown

^ #Start of string
(?=.{8,15}$) #Lookahead to check there are 8 to 15 digits
(?!.*?(.)\1{3}) #Lookahead to determine that there is no character repeating more than thrice
[A-Za-z0-9]+ #Match the characters
$ #End of string

For unicode support, you can use

^(?=.{8,15}$)(?!.*?(.)\1{3})[\p{L}\p{N}]+$

NOTE :- For matching one character and one digit, you can use

^(?=.{8,15}$)(?=.*[A-Za-z])(?=.*\d)(?!.*?(.)\1{3})[A-Za-z0-9]+$

Regex Demo