c＃条件正则表达式字符串匹配

Question

I am trying to use c# Regular Expression to match a particular string of characters but I can not figure out how to do it. Any help is appreciated.

The string that I am trying to match is as follows, where A is an uppercase alpha character, X is an upper case alpha-numeric character and # is 0, 1 or 2.

AA-#-XX-X-XXX-XXXXXXX-XXXXXXXX

So any of the following would match the string above.

XY-1

MM-0-AB

MM-0-AB-1-ABC-1234567

VV-2-XX-7-CCC-ABCDEFG-12345678

Any any of the following would NOT match.

QQ-7-AA (Only 0, 1, 2 are allowed at the second level.)

QQ-2-XX-7-CC (Partial characters for that level.)

QQ-2-XX-7-CCC-ABCDEFG- (Can not end in a dash.)

QQ-2-XX-7-CCC-ABCDEFG-123456 (Partial characters for that level.)

So far (not that far really) I have as the pattern to match @"^[AZ]{2}" , but I am unsure how to match conditionally (I'm not even sure if conditionally is the proper term to use) the rest of the string, but only if it is there. Do I need to write 7 different statements for this? Seems unreasonable, but I could be wrong.

Answer 1

Have a look at the Regular Expression Language . You need the following elements:

• uppercase alpha character: [AZ]
• upper case alpha-numeric character: [A-Z0-9]
• 0, 1 or 2: [0-2]

• dash: -

• match x exactly n times: x{n}

• match x zero or one time: x?
• define a subexpression: ( ... )

Examples:

• two uppercase alpha characters: [AZ]{2}
• two uppercase alpha characters, followed by a dash: [AZ]{2}-
• two uppercase alpha characters, followed by a dash, followed by 0, 1 or 2: [AZ]{2}-[0-2]
• two uppercase alpha characters, followed by a dash, followed by 0, 1 or 2, but with the subexpression consisting of the dash and 0, 1 or 2 occurring zero or one time:
  [AZ]{2}(-[0-2])?
• and so on...

Resulting expression:

^[A-Z]{2}(-[0-2](-[A-Z0-9]{2}(-[A-Z0-9](-[A-Z0-9]{3}(-[A-Z0-9]{7}(-[A-Z0-9]{8})?)?)?)?)?)?$