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Regex match multiple digits after '-'

This seems like it should be easy, but I'm not so good with regex, and this doesn't seem to be easy to find on google.
I need a regex that starts with the string 'SP-multiple digits' and ends with the string '- multiple digits'
For example i have to match '-12' in "Sp-1234-12".
My attempt was: [^*-]*$ -> This case matches everything after the minus but i need the minus included.

For that digit and hyphen format, you could use a capture group for the part of the string that you want:
^Sp(?:-\d+)*(-\d+)$
Explanation
^ Start of string
Sp Match literally
(?:-\d+)* Optionally repeat - and 1+ digits
(-\d+) Capture group 1, match - and 1+ digits
$ End of string
Regex demo
Note that in C# you can use [0-9] instead of \d to match only digits 0-9

Regex to match 7 same digits in a number regardless of position

I want to match an 8 digit number. Currently, I have the following regex but It is failing in some cases.
(\d+)\1{6}
It matches only when a number is different at the end such as 44444445 or 54444444. However, I am looking to match cases where at least 7 digits are the same regardless of their position.
It is failing in cases like
44454444
44544444
44444544
What modification is needed here?

It's probably a bad idea to use this in a performance-sensitive location, but you can use a capture reference to achieve this.
The Regex you need is as follows:
(\d)(?:.*?\1){6}
Breaking it down:
(\d) Capture group of any single digit
.*? means match any character, zero or more times, lazily
\1 means match the first capture group
We enclose that in a non-capturing group {?:
And add a quantifier {6} to match six times

You can sort the digits before matching
string input = "44444445 54444444 44454444 44544444 44444544";
string[] numbers = input.Split(' ');
foreach (var number in numbers)
{
number = String.Concat(str.OrderBy(c => c));
if (Regex.IsMatch(number, #"(\d+)\1{6}"))
// do something
}
Still not a good idea to use regex for this though

The pattern that you tried (\d+)\1{6} matches 6 of the same digits in a row. If you want to stretch the match over multiple same digits, you have to match optional digits in between.
Note that in .NET \d matches more digits than 0-9 only.
If you want to match only digits 0-9 using C# without matching other characters in between the digits:
([0-9])(?:[0-9]*?\1){6}
The pattern matches:
([0-9]) Capture group 1
(?: Non capture group
[0-9]*?\1 Match optional digits 0-9 and a backreference to group 1
){6} Close non capture group and repeat 6 times
See a .NET Regex demo
If you want to match only 8 digits, you can use a positive lookahead (?= to assert 8 digits and word boundaries \b
\b(?=\d{8}\b)[0-9]*([0-9])(?:[0-9]*?\1){6}\d*\b
See another .NET Regex demo

Regex matching recurring patterns

I want to validate input in a C# TextBox by using regular expressions. The expected input is in this format:
CCCCC-CCCCC-CCCCC-CCCCC-CCCCC-CCCCC-C
So I've got six elements of five separated characters and one separated character at the end.
Now my regex matches any character between five and 255 chars: .{5,255}
How do I need to modify it in order to match the format mentioned above?

Update: -
If you want to match any character, then you can use: -
^(?:[a-zA-Z0-9]{5}-){6}[a-zA-Z0-9]$
Explanation: -
(?: // Non-capturing group
[a-zA-Z0-9]{5} // Match any character or digit of length 5
- // Followed by a `-`
){6} // Match the pattern 6 times (ABCD4-) -> 6 times
[a-zA-Z0-9] // At the end match any character or digit.
Note: - The below regex will only match pattern like you posted: -
CCCCC-CCCCC-CCCCC-CCCCC-CCCCC-CCCCC-C
You can try this regex: -
^(?:([a-zA-Z0-9])\1{4}-){6}\1$
Explanation: -
(?: // Non-capturing group
( // First capture group
[a-zA-Z0-9] // Match any character or digit, and capture in group 1
)
\1{4} // Match the same character as in group 1 - 4 times
- // Followed by a `-`
){6} // Match the pattern 6 times (CCCCC-) -> 6 times
\1 // At the end match a single character.

Untested, but I think this will work:
([A-Za-z0-9]{5}-){6}[A-Za-z0-9]

For your example, in general replace C to the character class you want:
^(C{5}-){6}C$
^([a-z]{5}-){6}[a-z]$ # Just letter, use case insensitive modifier
^([a-z0-9]{5}-){6}[a-z0-9]$ # Letters and digits..

Try this:
^(C{5}-){6}C$
The ^ and $ denote the begiining and end of the string repectively and make sure that no additional characters are entered.

Regular Expression: Section names with unknown length?

I have a text block that is formatted like this:
1.2.3.4.5 or 1.2222.3.4.5 or 1 or 1.2 etc
An unknow number of numbers and dots (sections of a legal document)
How can I capture the full section (1.2.3.4.5) into a group?
I use C# but any regex is fine, aI can translate it.

UPDATED
Use this Regex:
Regex.Matches(inputString, #"\d[\.\d]*(?<!\.)");
explain:
\d digits (0-9)
[.\d]* any character of: '.', digits (0-9)
(0 or more times, matching the most amount possible))
(?<! subexpression) Zero-width negative lookbehind assertion.

string s = "1.2.3.4.5 or 1.2222.3.4.5 or 1 or 1.2 or 2222.3333.111.5 etc";
var matches = Regex.Matches(s, #"\d+(\.\d+)*").Cast<Match>()
.Select(m => m.Value)
.ToArray();

well, if you know you can't go beyond 5, then you can do
#"1+((.2+)((.3+)((.4+)(.5+)?)?)?)?"
and you can expand on that pattern for every symbol, up to a finite number of symbols
the + means any number of occurrences of the symbol, but at least 1. IF 0 is valid, you can use * instead
put ?: after an opening parenthesies if you don't want the pattern to be captured
like example: (?:abc)
I ommitted them to make the regex more readable.
the ? after the parenthesies, means 1 or 0 of the preceding symbol.
Now if you don't know how far you string can go, for instance
"1.2.3.4......252525.262626.272727.......n.n.n" than my intuition tells me that you can't do that with regex.

RegEx for limited decimal

New to regex syntax here. Trying to write a regex to provide some input validation.
What I need is a regex to match a whole number, or a decimal with exactly one digit past the decimal.
Good Match
1
12
100
1.1
100.1
1.0
No Match
1.22
1.
0
012
Here is what I came up with but it doesn't work:
Regex.IsMatch(paidHours, "\\d+[.]?[0-9]?")

You can try with:
Regex.IsMatch(paidHours, "^\\d+(\\.\\d)?$")

Regex.IsMatch(paidHours, #"^\d+(\.\d)?$")

Edited answer after OP question edit.
Regex.IsMatch(paidHours, #"^[1-9][0-9]*(\.[0-9])?$");
Explanation:
^ : Start of the String
[1-9] : A single number between 1 and 9
[0-9]* : Zero or more number(s) between 0 and 9
([0-9]? would match zero or one number and the String "100" would not match the regex)
( : Start of a group
\. : A point
[0-9] : A single number between 0 and 9
)? : End of the group. The group must be repeated zero or one time
$ : End of the String
Please note that \d is not exactly equivalent to [0-9]: \d matches any unicode digit. For instance, this character ௮ will be matched if you use \d but won't be if you use [0-9].

Try to specify beggining/end of the line:
#"^\d+[.]?[0-9]?$"
You regex won't work since ie 1.234 was a match wit 1.2, if you don't specify you want the string ends with the '$' sign.