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Regular Expression for UK postcodes

I have a list of post codes which should be excluded from my shipping methods.
Suppose I have to exclude Scilly Isles, Isle of Man and few others.
For the above 2 areas valid post codes are IM1-IM9, IM86, IM87, IM89. And if it is IM25 or IM85 it is invalid.
I have writtent following expression. But it is returning even it is IM25 or IM 85.
var regex = new Regex("(PO3[0-9]|PO4[0-1]|GY[1-9]|JE[1-5]|IM[1-9]|TR[1-9])");
If I am passing IM85, to my expression it should return false. for IM1-IM9,, IM86, IM87, IM89 it should return true.
Same with TR post codes also. TR1-TR27 is a valid post code. If I give TR28, it should return false.
I am using '|' to seperate multiple patterns. Is that the right way of including multiple patterns in 1 expression.

What do you expect? What should be matched and what not? And please give an example of the string you want to test.
If you match your pattern against "IM25" it will match because you do allow IM[1-9] in your pattern, so you get a valid partial match. If you want to avoid that (I am not sure what you want to achieve) and want to allow really only a single digit after the first letters, use a "word boundary" \b and specify exactly what you want to allow, something like this:
(PO3[0-9]|PO4[0-1]|GY[1-9]|JE[1-5]|IM([1-9]|8[6-9])|TR([1-9]|2[0-7]))\b
See it here on Regexr
this would allow for the "IM" part also 6-9 as a second digit when there is a 8 before.
Update
It is still not clear what the context of your task is. I assume you have a list of valid Postcodes, probably it would be better, you extract the post code or only the first part of it (for that you can eventually use a regex) and check if it is in the list or not.

The actual validation is on the wikipedia site... Google has the answers ;) http://en.wikipedia.org/wiki/Postcodes_in_the_United_Kingdom#Validation
(GIR 0AA)|(((A[BL]|B[ABDFHLNRSTX]?|C[ABFHMORTVW]|D[ADEGHLNTY]|E[HNX]?|F[KY]|G[LUY]?|H[ADGPRSUX]|I[GMPV]|JE|K[ATWY]|L[ADELNSU]?|M[EKL]?|N[EGNPRW]?|O[LX]|P[AEHLOR]|R[GHM]|S[AEGKLMNOPRSTY]?|T[ADFNQRSW]|UB|W[ADFNRSV]|YO|ZE)[1-9]?[0-9]|((E|N|NW|SE|SW|W)1|EC[1-4]|WC[12])[A-HJKMNPR-Y]|(SW|W)([2-9]|[1-9][0-9])|EC[1-9][0-9]) [0-9][ABD-HJLNP-UW-Z]{2})

I still think you need more clarification. As a huge Regex guy, I would like to point out that multi-digit ranges should try to be put into the code side, not the Regex side, just for your sanity. But I personally like to play with Regex in this way. Regex reads one character at a time, so it only recognizes zero through nine. Not ten, not twenty eight. If you want to allow the following:
28 through 347
Then it becomes pretty complicated.
To put it into words, you want to allow:
If Two Digits, allow 2-9 for the first digit, and:
If the first digit is a Two, then allow 8/9 for the second digit,
ElseIf the first Digit is 3-9, then allow 0-9 for the second digit
Elseif Three Digits, allow 1-3 for the first Digit, and:
If the first digit is a Three, then allow 0-4 for the second digit, and:
If the second digit is a Four, then allow 0-7 for the third digit,
ElseIf the second digit is 0-3, then allow 0-9 for the third digit.
ElseIf the first digit is 1/2, then allow 0-9 for both the Second and Third digits.
Then with that, you can write a proper Regex like so, which searches for a word boundary or non-Digit surrounding a 2-pair or 3-pair. With this type of Problem-Solving, you should be able to figure out your Regex issue. Otherwise, let us know more about EXACTLY What you want to Match and NOT Match:
(\b|\D)((2[89]|[3-9][0-9])(\b|\D)|(3(4[0-7]|[0-3][0-9])|[12][0-9][0-9])(\b|\D))

I have changed my approach.
Instead of going for a regular expression which is becoming more complex, I am saving all the excluded outward codes of UK post codes.
And if any post code contains the particular outward code, excluding the post code from the list.
Outward codes are in this format
XX-YYY
XXX-YYY
XXXX-YYY
In all above formats, X represents outward code of an UK postcode.

I need a Regular Expression allowing user to input numbers, plus, minus and parentheses

I need a Regular Expression allowing user to input numbers, plus, minus and parentheses.
User can only input:
At most one open parenthesis '('.
At most one close parenthesis ')'.
At most one plus '+'
As many minus '-' but not after each other.
Exactly 11 numbers.
Here are valid inputs:
(0)+12-3-4-56-7890
+)0(12345-678-90
+01234567890
+(01234567890)
01234567890
-01-234+5678-90
(01234567890)
)01234567890(
And following are not valid:
0123456--7890
0((1234567890
01234567890))
++01234567890
123456
++123456789
I'm using C# for programming and if it helps order of open and close parentheses can become mandatory too. so )01234567890( will not be valid.
Thanks in advance

This regex passes your examples, but might not be exactly what you're looking for. It should point you in the right direction.
^(?!.*-{2,})(?!(?:.*\)){2,})(?!(?:.*\(){2,})(?!\+{2,})(?:\D*\d\D*){11}$
(?!.*-{2,}) Cannot contain two or more hyphens.
(?!(?:.*)){2,}) Cannot contain two or more closing parentheses.
(?!(?:.*(){2,}) Cannot contain two or more opening parentheses.
(?!+{2,}) Cannot start with more than two addition symbols.
(?:\D*\d\D*){11} Must contain 11 instances of a numeric character surrounded by anything.
However, this is very confusing and fairly inefficient. I bet the regex could be rewritten to be much quicker, but won't be much easier to understand.
I suggest that you follow MisterJack's suggestion instead of pursue a regex. It'll be easier to maintain.
EDIT
^(?!.*--)(?!.*(\(|\)|\+).*\1)(?:\D*\d\D*){11}$
I've consolidated the parentheses and plus symbol rules into one negative lookahead using a backreference. This also restricts the number of parens and pluses to just one of each. I couldn't get it to restrict to just a certain set of characters, but you might be able to do that in a second pass with another regex.
^ Match from beginning of the string
(?!.*--) Do not allow consecutive hyphens
(?!.* ((|)|+).*\1) Do not allow two or more instances of () or +
(?:\D*\d\D*){11} Must contain 11 digits, allow non-digit characters before and after, such as hyphen.
$ Match to end of string
I tried a negative and positive lookahead to restrict the characters, but couldn't get it to work right. I also tried to replace \D with [()+-] but that didn't work either. Maybe someone else will add a comment to show how to restrict the characters. I'd sure love to see how someone else does it in this regex.

I think that a regular expression isn't your best bet, because it could become too much complicated and it can easily be broken.
What I suggest you is to try to parse your input, i.e. to count how many numbers, minuses, plus and parenthesis the user entered, and if they appear in the right order. An easy way to do this could be to loop over the characters that compose the string and check if the current char:
is a number (and we keep count of how many numbers we found)
is a minus (and the previous char isn't a minus)
is a plus (and it is the first one)
is a parenthesis (it's the first open parenthesis or it's a closed one and we already found the open parenthesis)
This could do the trick.

Shall this Regex do what I expect from it, that is, matching against "A1:B10,C3,D4:E1000"?

I'm currently writing a library where I wish to allow the user to be able to specify spreadsheet cell(s) under four possible alternatives:
A single cell: "A1";
Multiple contiguous cells: "A1:B10"
Multiple separate cells: "A1,B6,I60,AA2"
A mix of 2 and 3: "B2:B12,C13:C18,D4,E11000"
Then, to validate whether the input respects these formats, I intended to use a regular expression to match against. I have consulted this article on Wikipedia:
Regular Expression (Wikipedia)
And I also found this related SO question:
regex matching alpha character followed by 4 alphanumerics.
Based on the information provided within the above-linked articles, I would try with this Regex:
Default Readonly Property Cells(ByVal cellsAddresses As String) As ReadOnlyDictionary(Of String, ICell)
Get
Dim validAddresses As Regex = New Regex("A-Za-z0-9:,A-Za-z0-9")
If (Not validAddresses.IsMatch(cellsAddresses)) then _
Throw New FormatException("cellsAddresses")
// Proceed with getting the cells from the Interop here...
End Get
End Property
Questions
1. Is my regular expression correct? If not, please help me understand what expression I could use.
2. What exception is more likely to be the more meaningful between a FormatException and an InvalidExpressionException? I hesitate here, since it is related to the format under which the property expect the cells to be input, aside, I'm using an (regular) expression to match against.
Thank you kindly for your help and support! =)

I would try this one:
[A-Za-z]+[0-9]+([:,][A-Za-z]+[0-9]+)*
Explanation:
Between [] is a possible group of characters for a single position
[A-Za-z] means characters (letters) from 'A' to 'Z' and from 'a' to 'z'
[0-9] means characters (digits) from 0 to 9
A "+" appended to a part of a regex means: repeat that one or more times
A "*" means: repeat the previous part zero or more times.
( ) can be used to define a group
So [A-Za-z]+[0-9]+ matches one or more letters followed by one or more digits for a single cell-address.
Then that same block is repeated zero or more times, with a ',' or ':' separating the addresses.

Assuming that the column for the spreadsheet is any 1- or 2-letter value and the row is any positive number, a more complex but tighter answer still would be:
^[A-Z]{1,2}[1-9]\d*(:[A-Z]{1,2}[1-9]\d*)?(,[A-Z]{1,2}[1-9]\d*(:[A-Z]{1,2}[1-9]\d*)?)*$
"[A-Z]{1,2}[1-9]\d*" is the expression for a single cell reference. If you replace "[A-Z]{1,2}[1-9]\d*" in the above with then the complex expression becomes
^<cell>(:<cell>)?(,<cell>(:<cell>*)?)*$
which more clearly shows that it is a cell or a range followed by one or more "cell or range" entries with commas in between.
The row and column indicators could be further refined to give a tighter still, yet more complex expression. I suspect that the above could be simplified with look-ahead or look-behind assertions, but I admit those are not (yet) my strong suit.

I'd go with this one, I think:
(([A-Z]+[1-9]\d*:)?[A-Z]+[1-9]\d*,)*([A-Z]+[1-9]\d*:)?[A-Z]+[1-9]\d*
This only allows capital letters as the prefix. If you want case insensitivity, use RegexOptions.IgnoreCase.
You could simplify this by replacing [A-Z]+[1-9]\d* with plain old [A-Z]\d+, but that will only allow a one-letter prefix, and it also allows stuff like A0 and B01. Up to you.
EDIT:
Having thought hard about DocMax's mention of lookarounds, and using Hans Kesting's answer as inspiration, it occurs to me that this should work:
^[A-Z]+\d+((,|(?<!:\w*):)[A-Z]+\d+)*$
Or if you want something really twisted:
^([A-Z]+\d+(,|$|(?<!:\w*):))*(?<!,|:)
As in the previous example, replace \d+ with [1-9]\d* if you want to prevent leading zeros.
The idea behind the ,|(?<!\w*:): is that if a group is delimited by a comma, you want to let it through; but if it's a colon, it's only allowed if the previous delimiter wasn't a colon. The (,|$|...) version is madness, but it allows you to do it all with only one [A-Z]+\d+ block.
However! Even though this is shorter, and I'll admit I feel a teeny bit clever about it, I pity the poor fellow who has to come along and maintain it six months from now. It's fun from a code-golf standpoint, but I think it's best for practical purposes to go with the earlier version, which is a lot easier to read.

i think your regex is incorrect, try (([A-Za-z0-9]*)[:,]?)*
Edit : to correct the bug pointed out by Baud : (([A-Za-z0-9]*)[:,]?)*([A-Za-z0-9]+)
and finally - best version : (([A-Za-z]+[0-9]+)[:,]?)*([A-Za-z]+[0-9]+)
// ah ok this wont work probably... but to answer 1. - no i dont think your regex is correct
( ) form a group
[ ] form a charclass (you can use A-Z a-d 0-9 etc or just single characters)
? means 1 or 0
* means 0 or any
id suggest reading http://www.regular-expressions.info/reference.html .
thats where i learned regexes some time ago ;)
and for building expressions i use Rad Software Regular Expression Designer

Let's build this step by step.
If you are following an Excel addressing format, to match a single-cell entry in your CSL, you would use the regular expression:
[A-Z]{1,2}[1-9]\d*
This matches the following in sequence:
Any character in A to Z once or twice
Any digit in 1 to 9
Any digit zero or more times
The digit expression will prevent inputting a cell address with leading zeros.
To build the expression that allows for a cell address pair, repeat the expression preceded by a colon as optional.
[A-Z]{1,2}[1-9]\d*(:[A-Z]{1,2}[1-9]\d*)?
Now allow for repeating the pattern preceded by a comma zero or more times and add start and end string delimiters.
^[A-Z]{1,2}[1-9]\d*(:[A-Z]{1,2}[1-9]\d*)?(,[A-Z]{1,2}[1-9]\d*(:[A-Z]{1,2}[1-9]\d*)?)*$
Kind of long and obnoxious, I admit, but after trying enough variants, I can't find a way of shortening it.
Hope this is helpful.

What is the regular expression for the following strings and would the expression change if the number rolled over?

What would be the following regular expressions for the following strings?
56AAA71064D6
56AAA7105A25
Would the regular expression change if the numbers rolled over? What I mean by this is that the above numbers happen to contain hexadecimal values and I don't know how the value changes one it reaches F. Using the first one as an example: 56AAA71064D6, if this went up to
56AAA71064F6 and then the following one would become 56AAA7106406, this would create a different regular expression because where a letter was allowed, now their is a digit, so does this make the regular expression even more difficult. Suggestions?
A manufacturer is going to enter a range of serial numbers. The problems are that different manufacturers have different formats for serial numbers (some are just numbers, some are alpha numeric, some contain extra characters like dashes, some contain hexadacimal values which makes it more difficult because I don't know how the roll over to the next serial number). The roll over issue is the biggest problem because the serial numbers are entered as a range like 5A1B - 6F12 and without knowing how the roll over, it seems to me that storing them in the database is not as easy. I was going to have the option of giving the user the option to input the pattern (expression) and storing that in the databse, but if a character or characters changes from a digit to a letter or vice versa, then the regular expression is no longer valid for certain serial numbers.
Also, the above example I gave is with just one case. There are multitude of serial numbers that would contain different expressions.

There's no single regular expression which is "the" expression to match both of those strings. Instead, there are infinitely many which will do so. Here are two options at opposite ends of the spectrum:
(56AAA71064D6)|(56AAA7105A25)
.*
The first will only match those two strings. The second will match anything. Both satisfy all the criteria you've given.
Now, if you specify more criteria, then we'd be able to give a more reasonable idea of the regular expression to provide - and that will drive the answers to the other questions. (At the moment, the only answer that makes sense is "It depends on what regex you use.")

I think you could do it this way for 12 characters. This will search for a 12 character phrase where each of the characters must be a capital (A or B or C or D or E or F or 1 or 2 or 3 or 4 or 5 or 6 or 7 or 8 or 9 or 0)
[A-F0-9]{12}
If you're wanting to include the possibility of dashes then do this.
[A-F0-9\-]{12}
Or you're wanting to include the possibility of dashes plus the 12 characters then do this. But that would pick up any 12-15 character item that fit the criteria though.
[A-F0-9\-]{12,15}
Or if it's surrounded by spaces (AAAAHHHh...SO is stripping out my spaces!!!)
[A-F0-9\-]{12}
Or if it's surrounded by tabs
\t[A-F0-9\-]{12}\t

This match a string that contains 12 hexa
[0-9A-F]{12}

Assuming these are all 12-digit hexadecimal numbers, which it looks like they are, the following regex should work:
[0-9A-Fa-f]{12}
Here I'm using a character class to say that I want any digit, OR A-F, OR a-f. As a bonus I'm allowing lowercase letters; if you don't want those just get them out of the regex.
As Jon Skeet and others have said, you really didn't provide enough information, so if you don't like this answer please understand that I was doing the best I can with what information you provided.

So, how about this:
[0-9A-F]{12}

Well it sounds like you're describing a 12 digit hexadecimal number:
^[A-F0-9]{12}$

Regex for Comma Separated Number or Just Number

This is something of a follow up from a previous question. The requirements have changed, and I'm looking for some help with coming up with regex for either a comma separated number or a number with no commas. Sample input is below, along with some failed attempts.
Any help is appreciated.
Acceptable input:
1,234,567
1234567
Unacceptable input:
1234,567
1,234567
Some failed attempts:
^(\d{1,3}(?:[,]\d{3})*)|((\d)*)$
^\d{1,3}((?:[,]?\d{3})*|(?:[,]\d{3})*)$
Original success:
^\d{1,3}(?:[,]\d{3})*$

Just add an "or one or more digits" to the end:
^(?:\d{1,3}(?:[,]\d{3})*|\d+)$
I think you had it almost right the first time and just didn't match up all your parentheses correctly.

Try this:
^\d{1,3}(?:(?:,\d{3})+|\d*)$
This will match any sequence that begins with one to three digits, followed by either
one or more segments of a comma followed by three digits, or
zero or more digits.

Why not use Int.TryParse() rathern then a regex?

Please see this answer for a definitive treatment of the “Is it a number?” question, including allowance for correctly comma-separated digit groups.

One thing i've noticed with all these is that the first bit of the regex allows for '0' based numbers to work. For example the number:
0,123,456
Would match using the accepted answer. I've been using:
((?<!\w)[+-]?[1-9][0-9]{,2}(?:,[0-9]{3})+)
Which also ensures that the number has nothing in front of it. It does not catch numbers of less then 1,000 however. This was to prevent ill-formatted numbers from being captured at all. If the final + were a ? the following numbers would be captured:
0,123
1,2 (as 2 separate numbers)
I have a strange set of numbers to match for (integers with commas, with spaces and without both), so i'm using pretty restrictive regexs to capture these groups.
Anyway, something to think about!