具有多个条件的正则表达式

Question

I'm trying to write a regular expression for checking numbers.

I should be able to identify the following:

• 999
• 99.99
• 99,99
• 99 9/9

But not the following 99M, 99BN, 99$.

So I thought this might work: string rule1 = @"\\b[0-9]+(?(.|,|\\n){0,1}[0-9]+)\\b";

[0-9]+ the first part says: I need 1 or more digits.

(?(.|,|\\n){0,1}[0-9]*) In this second part my intention was to express a condition:

If a point or a comma or a space comes after the first part then I need one or more numbers after the point, comma or space. But since I don't know a lot about regular expressions I'm stuck and getting a run-time exception.

Answer 1

I'm not really sure how you want to handle the last case, since as I said in a comment, there's a space in your example. But assuming that was supposed to be a line break, I believe something like this should work.

(\b\d+(\.|,|\/)?\d+\b)[^$]

Broken down:

(
\b           Word break
\d+          Any digit character (equivalent to your [0-9]), matched one or more times
(\.|,|\/)?   A period (escaped), comma, or slash (escaped), matched zero or one time.
\d+          Any digit character (equivalent to your [0-9]), matched one or more times
\b           Word break
)
[^$]         Avoid the last case, of 99$

I've tested this to the extent I can here .