CODEWITHSUNDEEP
c#asp.net.netregexdecimal
Victor Zakharov
Victor Zakharov

Reputation: 26424

Regex to validate a .NET's non-negative decimal or blank?

I'm looking for a regular expression that would validate a non-negative decimal (.NET type), i.e. if a non-negative value can be parsed using decimal.Parse(...), it should be considered valid. Otherwise invalid.

I'm okay if it fails the 28-29 significant digits validation - relying on user's sanity here - and then we have another validation layer that would catch it anyway.

Here is what I came up with:

^(?:[1-9]\d*|0)?(?:\.\d+)?$

Problem is that it rejects 1. which is a valid number (you can verify from the immediate window in VS). Could be other edge cases I did not test. Please advise.

P.S. I included ASP.NET and C# tags because this is for a web application written in C#, in which this regular expression is passed to a 3rd party component, which then works on the client (i.e. JS), so I cannot easily put custom code there (i.e. decimal.TryParse or smth like that).

Upvotes: 2

Views: 1036

Answers (1)

anubhava
anubhava

Reputation: 785008

You can use this regex based on a negative lookahead to avoid matching single dot:

^(?!\D+$)\+?\d*?(?:\.\d*)?$
  • (?!\D+$) is negative lookahead to assert failure when input is non digit characters
  • ?:\.\d*)? allows for matching 123. type of number.

RegEx Demo 1

RegEx Demo 2

Upvotes: 3

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