Regex syntax for single alpha character in string of digits

Question

I'm new to regex syntax and am looking for a way to match the following criteria:

String has 1 alpha character and the rest are digits
String starts with at least 1 digit but no more than 3
Following character is a single alpha character (upper or lower case a-Z)
Followed by 4 to 6 digits

Example valid data:

Most examples I'm finding are matching 1 or more of a value so I'm struggling with how to match specific number of characters and what place they can be found in.

For example:

Matching 1 or more digits at the start of the string: @"^\d"

or Making sure the string has at least one Alpha character:

bool match = Regex.IsMatch(tokenString, @"(?=.*[^a-zA-Z])", RegexOptions.IgnoreCase);

But this doesn't tell it that there can be only 1 alpha character.

1 or more digits at the start of the string. Use the OR (ie. | ) modifier in your Regex. I think that's what you are missing, if not let me link — Justin
– Justin, Commented Dec 20, 2013 at 17:26

Samuel Neff · Accepted Answer · 2013-12-20 17:25:21Z

6

This will work

^\d{1,3}[a-zA-Z]\d{4,6}$

breakdown:

^        - match at beginning
\d{1,3}  - one to three digits
[a-zA-Z] - one letter a-z or A-Z
\d{4,6}  - followed by between 4 and 6 digits
$        - and that's end of the string...

answered Dec 20, 2013 at 17:25

Samuel Neff

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Automate This Over a year ago

You guys make it look so easy :-) Thanks for the break down explanation.

Sabuj Hassan · Accepted Answer · 2013-12-20 17:24:49Z

3

Try using this one.

^\d{1,3}[a-zA-Z]\d{4,6}$

answered Dec 20, 2013 at 17:24

Sabuj Hassan

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Comments

Solomon Rutzky · Accepted Answer · 2013-12-20 17:24:59Z

3

The following pattern should do what you are asking for:

^\d{1,3}[a-zA-Z]\d{4,6}$

Well, since you are using RegexOptions.IgnoreCase, you can get away with just:

^\d{1,3}[a-z]\d{4,6}$

For more info on what you can do with Regular Expressions, go here:

http://www.regular-expressions.info/reference.html

answered Dec 20, 2013 at 17:24

Solomon Rutzky

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