Validating Thickness (Margin/Padding) string using Regex for different platforms

I have a specific Regex pattern requirement for a string pattern which contains margin/padding (Thickness) for max 3 different platform and devices separated by semicolon. Margin and Padding format is for .NET MAUI where you can have Universal, Horizontal/Vertical, LTRB.

Comma separated is Thickness (Margin) and semicolon separator is for different devices/platforms. Note that end of string shouldn't end with comma or semicolon.

Should Match (spaces are intentional for visibility)

• 10
• 10,10 ; 5,5
• 10,11,12,13 ; 20,30 ; 50

Shouldn't Match (spaces are intentional for visibility)

• 10 ,
• 10,10,999 ; 10,10 ,;
• 10,10 ; , 10;10,10
• 10 ;; 10

Tried this myself, but couldn't achieve above.

^((?:\d{1,3},?){1,4};?){1,3}$

You are matching an optional , and an optional ; on every repetition, which makes the regex also match strings like 123123123123 123123123123, 123123123123,;

• You could write the regex starting with 1-3 digits
• Then optionally repeat a grouped part where the comma is mandatory
• Then optionally repeat that whole part again where the semicolon is mandatory

For example:

^\d{1,3}(?:,\d{1,3}){0,3}(?: ; \d{1,3}(?:,\d{1,3}){0,3})*$

The regex in parts matches:

• ^ Start of string
• \d{1,3} Match 1-3 digits
• (?:,\d{1,3}){0,3} Repeat 0-3 times matching , and 1-3 digits
• (?: Non capture group to repeat as a whole part
  • ; \d{1,3} Match ; and 1-3 digits
  • (?:,\d{1,3}){0,3} Repeat 1-3 times matching , and 1-3 digits
• )* Close the non capture group and optionally repeat it
• $ End of string

See a regex 101 demo

If you want to match either 1, 2 or 4 numbers separated by a comma:

^\d{1,3}(?:,\d{1,3}|(?:,\d{1,3}){3})?(?: ; \d{1,3}(?:,\d{1,3}|(?:,\d{1,3}){3})?)*$

See another regex 101 demo

If you want to match optional spaces around the semicolon, then you could use *; * or just a ; if there should be no spaces.

A more broader match is using \s*;\s* but note that is could also possibly match newlines.