Question

I want a regular expression for decimal input, which can take 4 digits before decimal or comma and 2 digits after decimal/comma. 5 digit number without decimal is invalid. Also can accept null.

Correct Values can be:

1, 1111, 2222.56, 0.99, 9999.5

Invalid

88888, 8.888,

Validation show also include comma along with decimal.

If possible, then also explain the expression.

Answer 1

Regex.IsMatch(strInput, @"[\d]{1,4}([.,][\d]{1,2})?");

and explain:

[\d]{1,4}    any character of: digits (0-9) between 1 and 4 times

[.,]         any character of: '.', ','

[\d]{1,2}    any character of: digits (0-9) between 1 and 2 times

(...)?       match the expression or not (zero or one)