Develop Reference

Insert - after every second Character

so I'm developimg a Game with Unity 3D using C#. As first step the user has to enter his personal Code, which consists of 5 pairs, where each pairs has 2 characters/numbers (Im validating the characters & numbers separately). Now what I'm trying to achieve is that after every second character there should appear a minus, like you have after every 4th number, when you enter your credit-card number.
Example: 27-05-AB-CD-EF
So now I tried to use a Regular Expression and its working for the first two letters, but somehow the Regex does see the minus as a character too, and then it adds a minus infinitely often. I tried different versions, where i thought that i just allow letters and numbers, but somehow that doesn't work.
Regex.Replace(codeText, "([A-Za-z0-9][^-]){2}", "$0-");
Any guess what might be doing wrong?

Try with this expression "([A-Za-z0-9]){2}(?!-)" where (?!-) is a Zero-width negative lookahead assertion which in case you don't know is an expression that is matched but isn't part of the match value. So this expression matches two characters that aren't followed by -.
https://www.regular-expressions.info/lookaround.html read this page for more information

Regular expression with only numbers, dots and minimum value

Im trying to make a regular expression that accept only numbers, dots and that has minimum value and max value.
E.g:
1.000 - valid
100.000 - valid
100.000a -not valid
.10 - not valid
100 - not valid
I have this, which works as i want with numbers and dots, only one thing is missing here, and that is minimum and maximum validation.
#"^([+-]?\d{1,3}(?:,\d{1,3})*(?:\.\d+)*)$"
PS:
Im using data annotations on .net core
Update
I have a javascript that separates users input in input field to thousand format like:
From: 1000000
To: 1.000.000
For better user experience.
But, the problem is the validation with data annotations.
With the RegularExpression i have above is working with the dots, i just need a minimum and maximum value.
I have tried with Range(min, max), but it recognise it as an invalid input because of the dots.
Regards

Given your comment I assume this is what your after:
^[+-]?[1-9]\d{0,2}(?:\.\d{3})+$
It matches a range of 1-3 digits (the first not being a 0), then followed by at least one (no upper limit) sequence of . + three digits.
This will match any number larger than one thousand with . as thousand separators. And since your attempt allowed it, this also allows an optional sign in the beginning.
See it in action here at regexstorm. Note! I can't get $ and multiline to work there so a \s is used instead to illustrate.

Considering that after every number there is space character in the string
This should do the job :
regex = #"[0-9]{1,3}\.[0-9]{1,5}"
Update :
As the obtained text will be numbers , so you could simply validate them for a range check .
For reference please have a look :regex reference
Let me know , if it doesn't works

Regular Expressions C#

I know there are many questions about making regular expressions, but they all seem to be about a single problem than the general usage. I, too, have a problem like to solve. I have tried to learn by reading about regular expressions, but it gets tricky quick. Here's my question:
C#
I need to validate two textboxes that exist on the same form. The math operations I've coded can handle any floating point number. For this particular application I know of three formats the numbers will be in or there is a mistake on the users behalf. I'd like to prevent those mistakes in example if an extra number is accidentally typed or if enter is hit too early, etc.
Here are the formats: "#.####" "##.####" "###.##" where the "#" represents a mandatory digit. The formats starting with a one or two digit whole number must have 4 trailing digits or more. I've capped it at 8, or so I tried to lol.The format starting with a three digit whole number should never be allowed to have more than two digits trailing the decimal.
Here's what I have tried thus far.
Regex acceptedInputRegex = new Regex(#"^\b[0-9]{3}.[0-9]{2}|[0-9]{1,2}.[0-9]{4,8}$");
Regex acceptedInputRegex = new Regex(#"^\b\d{3}.\d{2} | \d{1,2}.\d{4,8}$");
I have tried it in thinking a match was what I wanted to achieve and as if a match to my negated expression means there is a problem. I was unsuccessful in both attempts. This is the code:
if (acceptedInputRegex.IsMatch(txtMyTextBox1.Text) || acceptedInputRegex.IsMatch(txtMyTextBox2.Text))
{
} else
{
MessageBox.Show("Numbers are not in the right format", "Invalid Input!");
return;
}
Are regular expressions what I should be using to solve this problem?
If not, please tell me what you recommend. If so, please help me correct my regex.
Thanks.

You are close, you need to escape the dots and group the alternatives so that the ^ and $ anchors could be applied to both of them:
#"^(?:\d{3}\.\d{2}|\d{1,2}\.\d{4,8})$"
See the regex demo.
Details:
^ - start of string
(?: - start of a non-capturing group matching either of the two alternatives:
\d{3}\.\d{2} - 3 digits, . and 2 digits
| - or
\d{1,2}\.\d{4,8} - 1 or 2 digits, ., 4 to 8 digits
) - end of the non-capturing group
$ - end of string.
To make \d match only ASCII digits, use RegexOptions.ECMAScript option:
var isValid = Regex.IsMatch(s, #"^(?:\d{3}\.\d{2}|\d{1,2}\.\d{4,8})$", RegexOptions.ECMAScript);

Validating Positive number with comma and period

I need a regular expression validation expression that will
ALLOW
positive number(0-9)
, and .
DISALLOW
letter(a-z)
any other letter or symbol except . and ,
for example, on my asp.net text box, if I type anything#!#--, the regular expression validation will disallow it, if I type 10.000,50 or 10,000.50 it should allowed.
I've been trying to use this regex:
^\d+(\.\d\d)?$
but my textbox also must allow , symbol and I tried using only integer regex validation, it did disallow if I type string, but it also disallow . and , symbol while it should allow number(0-9) and also . and , symbol

Don't Use \d to match [0-9] in .NET
First off, in .NET, \d will match any digits in any script, such as:
654۳۲١८৮੪૯୫୬१७੩௮௫౫೮൬൪๘໒໕២៧៦᠖
So you really want to be using [0-9]
Incomplete Spec
You say you want to only allow "digits, commas and periods", but I don't think that's the whole spec. That would be ^[0-9,.]+$, and that would match
...,,,
See demo.
Tweaking the Spec
It's hard to guess what you really want to allow: would 10,1,1,1 be acceptable?
We could start with something like this, to get some fairly well-formed strings:
^(?:[0-9]+(?:[.,][0-9]+)?|[1-9][0-9]{0,2}(?:(?:\.[0-9]{3})*|(?:,[0-9]{3})*)(?:\.[0-9]+)?)$
Play with the demo, see what should and shouldn't match... When you are sure about the final spec, we can tweak the regex.
Sample Matches:
0
12
12.123
12,12
12,123,123
12,123,123.12456
12.125.457.22
Sample Non-Matches:
12,
123.
1,1,1,1

Your regex would be,
(?:\d|[,\.])+
OR
^(?:\d|[,\.])+$
It matches one or more numbers or , or . one or more times.
DEMO

Maybe you can use this one (starts with digit, ends with digit):
(\d+[\,\.])*\d+
If you need more sophisticated price Regex you should use:
(?:(?:[1-9]\d?\d?([ \,\.]?\d{3})*)|0)(?:[\.\,]\d+)?
Edit: To make it more reliable (and dont get 00.50) you can add starting and ending symbol check:
(^|\s)(?:(?:[1-9]\d?\d?([ \,\.]?\d{3})*)|0)(?:[\.\,]\d+)($|\s)?

I think the best regex for your condition will be :
^[\d]+(?:,\d+)*(?:\.\d+)?$
this will validate whatever you like
and at the same time:
not validate:
numbers ending in ,
numbers ending in .
numbers having . before comma
numbers having more than one decimal points
check out the demo here : http://regex101.com/r/zI0mJ4

Your format is a bit strange as it is not a standard format.
My first thought was to put a float instead of a string and put a Range validation attribute to avoid negative number.
But because of formatting, not sure it would work.
Another way is the regex, of course.
The one you propose means :
"some numbers then possibly a group formed by a dot and two numbers exactly".
This is not what you exepected.
Strictly fitted your example of a number lower than 100,000.99 one regex could be :
^[0-9]{1-2}[\.,][0-9]{3}([\.,][0-9]{1-2})?$
A more global regex, that accept all positive numbers is the one posted by Avinash Raj : (?:\d|[,\.])+

Should not allow single zero or 0.##

How do I restrict single zero in a numeric (Decimal may alow) textbox? Textbox can accept any number but it should not accept only zero or "0.##" as value.
For example: "900.55", "200.00" is valid but "0" and "0.105"is invalid.
I tried ^[1-9]\d\.?\d[0-9]* but it accepting the "0" and "0.##"

You're almost there.
^[1-9][0-9]*(\.[0-9]+)?$
The input must
start with a number 1-9
be followed by any sequence of 0-9
and optional:
a dot followed by one or more 0-9.
Notes:
This also disallows 3.. If you don't want that, replace the last + with a *.
You can use \d instead of [0-9]. I've used the latter to stay consistent with [1-9] and keep things simple.

I think you're close, but it may be easier to include the decimal and following digits in a group and make that entire group only allowable once like this one:
^[1-9][0-9]*(\.\d*)?
Also, here's a useful site for testing regular expressions.

I think it would be simpler to do this:
float result;
return float.TryParse(textBox1.Text, out result) && result < 1;

If the textbox only accepts valid numbers, and all you want to assert is that it is > 0. All you really need then is
^[1-9]
or if trailing prefix zero's are allowed
^0*[1-9]

You could alternatively write it using a negative lookahead:
^(?!0\b)\d+(\.\d*)?$
This has the added bonus of accepting numbers with a preceding 0 like 022.

I faced the same situation and solve this.
try out it.
#"[^0]*[0-9].\d{2}$