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Separate title string with no spaces into words

I want to find and separate words in a title that has no spaces.
Before:
ThisIsAnExampleTitleHELLO-WORLD2019T.E.S.T.(Test)"Test"'Test'[Test]
After:
This Is An Example Title HELLO-WORLD 2019 T.E.S.T. (Test) [Test] "Test" 'Test'
I'm looking for a regular expression rule that can do the following.
I thought I'd identify each word if it starts with an uppercase letter.
But also preserve all uppercase words as not to space them into A L L U P P E R C A S E.
Additional rules:
Space a letter if it touches a number: Hello2019World Hello 2019 World
Ignore spacing initials that contain periods, hyphens, or underscores T.E.S.T.
Ignore spacing if between brackets, parentheses, or quotes [Test] (Test) "Test" 'Test'
Preserve hyphens Hello-World
C#
https://rextester.com/GAZJS38767
// Title without spaces
string title = "ThisIsAnExampleTitleHELLO-WORLD2019T.E.S.T.(Test)[Test]\"Test\"'Test'";
// Detect where to space words
string[] split = Regex.Split(title, "(?<!^)(?=(?<![.\\-'\"([{])[A-Z][\\d+]?)");
// Trim each word of extra spaces before joining
split = (from e in split
select e.Trim()).ToArray();
// Join into new title
string newtitle = string.Join(" ", split);
// Display
Console.WriteLine(newtitle);
Regular expression
I'm having trouble with spacing before the numbers, brackets, parentheses, and quotes.
https://regex101.com/r/9IIYGX/1
(?<!^)(?=(?<![.\-'"([{])(?<![A-Z])[A-Z][\d+?]?)
(?<!^) // Negative look behind
(?= // Positive look ahead
(?<![.\-'"([{]) // Ignore if starts with punctuation
(?<![A-Z]) // Ignore if starts with double Uppercase letter
[A-Z] // Space after each Uppercase letter
[\d+]? // Space after number
)
Solution
Thanks for all your combined effort in answers. Here's a Regex example. I'm applying this to file names and have exclude special characters \/:*?"<>|.
https://rextester.com/FYEVE73725
https://regex101.com/r/xi8L4z/1

Here is a regex which seems to work well, at least for your sample input:
(?<=[a-z])(?=[A-Z])|(?<=[0-9])(?=[A-Za-z])|(?<=[A-Za-z])(?=[0-9])|(?<=\W)(?=\W)
This patten says to make a split on a boundary of one of the following conditions:
what precedes is a lowercase, and what precedes is an uppercase (or
vice-versa)
what precedes is a digit and what follows is a letter (or
vice-versa)
what precedes and what follows is a non word character
(e.g. quote, parenthesis, etc.)
string title = "ThisIsAnExampleTitleHELLO-WORLD2019T.E.S.T.(Test)[Test]\"Test\"'Test'";
string[] split = Regex.Split(title, "(?<=[a-z])(?=[A-Z])|(?<=[0-9])(?=[A-Za-z])|(?<=[A-Za-z])(?=[0-9])|(?<=\\W)(?=\\W)");
split = (from e in split select e.Trim()).ToArray();
string newtitle = string.Join(" ", split);
This Is An Example Title HELLO-WORLD 2019 T.E.S.T. (Test) [Test] "Test" 'Test'
Note: You might also want to add this assertion to the regex alternation:
(?<=\W)(?=\w)|(?<=\w)(?=\W)
We got away with this here, because this boundary condition never happened. But you might need it with other inputs.

First few parts are similar to #revo answer: (?<!^|[A-Z\p{P}])[A-Z]|(?<=\p{P})\p{P}, additionally I add the following regex to space between number and letter: (?<=[a-z])(?=\d)|(?<=\d)(?=[a-z])|(?<=[A-Z])(?=\d)|(?<=\d)(?=[A-Z]) and to detect OTPIsADevice then replace with lookahead and lookbehind to find uppercase with a lowercase: (((?<!^)[A-Z](?=[a-z]))|((?<=[a-z])[A-Z]))
Note that | is or operator which allowed all the regex to be executed.
Regex: (?<!^|[A-Z\p{P}])[A-Z]|(?<=\p{P})\p{P}|(?<=[a-z])(?=\d)|(?<=\d)(?=[a-z])|(?<=[A-Z])(?=\d)|(?<=\d)(?=[A-Z])|(((?<!^)[A-Z](?=[a-z]))|((?<=[a-z])[A-Z]))
Demo
Update
Improvised a bit:
From: (?<!^|[A-Z\p{P}])[A-Z]|(?<=\p{P})\p{P}|(?<=[a-z])(?=\d)|(?<=\d)(?=[a-z])|(?<=[A-Z])(?=\d)|(?<=\d)(?=[A-Z])
into: (?<!^|[A-Z\p{P}])[A-Z]|(?<=\p{P})\p{P}|(?<=\p{L})\d which do the same thing.
(((?<!^)(?<!\p{P})[A-Z](?=[a-z]))|((?<=[a-z])[A-Z]))|(?<!^)(?=[[({&])|(?<=[)\]}!&}]) improvised from OP comment which is adding exception to some punctuation: (((?<!^)(?<!['([{])[A-Z](?=[a-z]))|((?<=[a-z])[A-Z]))|(?<!^)(?=[[({&])|(?<=[)\\]}!&}])
Final regex:
(?<!^|[A-Z\p{P}])[A-Z]|(?<=\p{P})\p{P}|(?<=\p{L})\d|(((?<!^)(?<!\p{P})[A-Z](?=[a-z]))|((?<=[a-z])[A-Z]))|(?<!^)(?=[[({&])|(?<=[)\]}!&}])
Demo

Aiming for simplicity rather than huge regex, I would recommend this code with small simple patterns (comments with explanation are in code):
string str = "ThisIsAnExampleTitleHELLO-WORLD2019T.E.S.T.(Test)\"Test\"'Test'[Test]";
// insert space when there is small letter followed by upercase letter
str = Regex.Replace(str, "(?<=[a-z])(?=[A-Z])", " ");
// insert space whenever there's digit followed by a ltter
str = Regex.Replace(str, #"(?<=\d)(?=[A-Za-z])", " ");
// insert space when there's letter followed by digit
str = Regex.Replace(str, #"(?<=[A-Za-z])(?=\d)", " ");
// insert space when there's one of characters ("'[ followed by letter or digit
str = Regex.Replace(str, #"(?=[(\[""'][a-zA-Z0-9])", " ");
// insert space when what preceeds is on of characters ])"'
str = Regex.Replace(str, #"(?<=[)\]""'])", " ");

You could reduce the requirements to shorten the steps of a regular expression using a different interpretation of them. For example, the first requirement would be the same as to say, preserve capital letters if they are not preceded by punctuation marks or capital letters.
The following regex works almost for all of the mentioned requirements and may be extended to include or exclude other situations:
(?<!^|[A-Z\p{P}])[A-Z]|(?<=\p{P})\p{P}
You have to use Replace() method and use $0 as substitution string.
See live demo here
.NET (See it in action):
string input = #"ThisIsAnExample.TitleHELLO-WORLD2019T.E.S.T.(Test)""Test""'Test'[Test]";
Regex regex = new Regex(#"(?<!^|[A-Z\p{P}])[A-Z]|(?<=\p{P})\p{P}", RegexOptions.Multiline);
Console.WriteLine(regex.Replace(input, #" $0"));

C# Extract part of the string that starts with specific letters

I have a string which I extract from an HTML document like this:
var elas = htmlDoc.DocumentNode.SelectSingleNode("//a[#class='a-size-small a-link-normal a-text-normal']");
if (elas != null)
{
//
_extractedString = elas.Attributes["href"].Value;
}
The HREF attribute contains this part of the string:
gp/offer-listing/B002755TC0/
And I'm trying to extract the B002755TC0 value, but the problem here is that the string will vary by its length and I cannot simply use Substring method that C# offers to extract that value...
Instead I was thinking if there's a clever way to do this, to perhaps a match beginning of the string with what I search?
For example I know for a fact that each href has this structure like I've shown, So I would simply match these keywords:
offer-listing/
So I would find this keyword and start extracting the part of the string B002755TC0 until the next " / " sign ?
Can someone help me out with this ?

This is a perfect job for a regular expression :
string text = "gp/offer-listing/B002755TC0/";
Regex pattern = new Regex(#"offer-listing/(\w+)/");
Match match = pattern.Match(text);
string whatYouAreLookingFor = match.Groups[1].Value;
Explanation : we just match the exact pattern you need.
'offer-listing/'
followed by any combination of (at least one) 'word characters' (letters, digits, hyphen, etc...),
followed by a slash.
The parenthesis () mean 'capture this group' (so we can extract it later with match.Groups[1]).
EDIT: if you want to extract also from this : /dp/B01KRHBT9Q/
Then you could use this pattern :
Regex pattern = new Regex(#"/(\w+)/$");
which will match both this string and the previous. The $ stands for the end of the string, so this literally means :
capture the characters in between the last two slashes of the string

Though there is already an accepted answer, I thought of sharing another solution, without using Regex. Just find the position of your pattern in the input + it's lenght, so the wanted text will be the next character. to find the end, search for the first "/" after the begining of the wanted text:
string input = "gp/offer-listing/B002755TC0/";
string pat = "offer-listing/";
int begining = input.IndexOf(pat)+pat.Length;
int end = input.IndexOf("/",begining);
string result = input.Substring(begining,end-begining);
If your desired output is always the last piece, you could also use split and get the last non-empty piece:
string result2 = input.Split(new string[]{"/"},StringSplitOptions.RemoveEmptyEntries)
.ToList().Last();

Extract tables and columns from SQL query using regular expression

I am trying to create a regex for this task, but I really can't grasp the understanding of regex apart from very simple cases :-( :
The problem: I have this ("SQL like") query:
SELECT tcmcs003.*, tccom130.nama, tccom705.dsca, tcmcs052.dsca, tccom100.nama
FROM tcmcs003, tccom130,tccom705,tcmcs052,tccom100
WHERE tcmcs003.cadr REFERS TO tccom130
AND tcmcs003.casi REFERS TO tccom705
AND tcmcs003.cprj REFERS TO tcmcs052
AND tcmcs003.bpid REFERS TO tccom100
ORDER BY tcmcs003._index1
I want to "extract" all the table names and column names, and after that I want to simply add my characters to them...
For example replace:
SELECT tcmcs003.*, tccom130.nama
with:
SELECT tcmcs003XXX.*, tccom130XXX.namaYYY
Up to now I have the "best" regex I have is this:
(?<gselect>SELECT\s+)*(?<tname>\w{5}\d{3})*(?<spaces>[\.\,\s])+(?<colname>\w{4})*
And replacement pattern:
${gselect}${tname}XXX${spaces}${colname}YYY
The output is really terrible :-(
SELECT tcmcs003.
m130
.nama
m705
.dsca
s052
.dsca
m100
.nama
FROM
s003
m130
,m705
,s052
,m100
WHER
s003
.cadr
REFE
m130
s003
How can I write the regex?
I want to capture repeteately something like
[(any string)(table name)(\.a dot or not)(column name)(any string) ] (repeat N times)
EDIT
I am writing in C#
The pattern should be a bit more general that:
\b(tc(?:mcs|com)\d{3}XXX.\w+)\b
in the sense that table name is 5 characters (the first is always a t, followed by 4 random chars) followed by 3 random digits
table column is 4 random chars

Instead of trying to match the whole command, I'll simply match each table or column independently. Since tables have digits in its name, there's few chances it could match something else.
Match column names with:
\b(t\w{4}\d{3}\.\w{4})\b
Match table names with:
\b(t\w{4}\d{3})\b
Then, we can replace each with the desired value: "$1YYY" and "$1XXX" respectively. The patterns use these constructs:
\b Matches a word boundary (a word char on one side and not a word char on the other).
\w{4} Matches 4 word chars ([A-Za-z0-9_]).
\d{3} Matches 3 digits ([0-9]).
Code:
string input = #"SELECT tcmcs003.*, tccom130.nama, tccom705.dsca, tcmcs052.dsca, tccom100.nama
FROM tcmcs003, tccom130,tccom705,tcmcs052,tccom100
WHERE tcmcs003.cadr REFERS TO tccom130
AND tcmcs003.casi REFERS TO tccom705
AND tcmcs003.cprj REFERS TO tcmcs052
AND tcmcs003.bpid REFERS TO tccom100
ORDER BY tcmcs003._index1";
string Pattern1 = #"\b(t\w{4}\d{3}\.\w{4})\b";
string Pattern2 = #"\b(t\w{4}\d{3})\b";
Regex r1 = new Regex(Pattern1);
Regex r2 = new Regex(Pattern2);
string replacement1 = "YYY";
string replacement2 = "XXX";
string result = "";
result = r1.Replace(input, "$1" + replacement1);
result = r2.Replace(result, "$1" + replacement2);
Console.WriteLine(result);
ideone Demo

Get sub-strings from a string that are enclosed using some specified character

Suppose I have a string
Likes (20)
I want to fetch the sub-string enclosed in round brackets (in above case its 20) from this string. This sub-string can change dynamically at runtime. It might be any other number from 0 to infinity. To achieve this my idea is to use a for loop that traverses the whole string and then when a ( is present, it starts adding the characters to another character array and when ) is encountered, it stops adding the characters and returns the array. But I think this might have poor performance. I know very little about regular expressions, so is there a regular expression solution available or any function that can do that in an efficient way?

If you don't fancy using regex you could use Split:
string foo = "Likes (20)";
string[] arr = foo.Split(new char[]{ '(', ')' }, StringSplitOptions.None);
string count = arr[1];
Count = 20
This will work fine regardless of the number in the brackets ()
e.g:
Likes (242535345)
Will give:
242535345

Works also with pure string methods:
string result = "Likes (20)";
int index = result.IndexOf('(');
if (index >= 0)
{
result = result.Substring(index + 1); // take part behind (
index = result.IndexOf(')');
if (index >= 0)
result = result.Remove(index); // remove part from )
}
Demo

For a strict matching, you can do:
Regex reg = new Regex(#"^Likes\((\d+)\)$");
Match m = reg.Match(yourstring);
this way you'll have all you need in m.Groups[1].Value.
As suggested from I4V, assuming you have only that sequence of digits in the whole string, as in your example, you can use the simpler version:
var res = Regex.Match(str,#"\d+")
and in this canse, you can get the value you are looking for with res.Value
EDIT
In case the value enclosed in brackets is not just numbers, you can just change the \d with something like [\w\d\s] if you want to allow in there alphabetic characters, digits and spaces.

Even with Linq:
var s = "Likes (20)";
var s1 = new string(s.SkipWhile(x => x != '(').Skip(1).TakeWhile(x => x != ')').ToArray());

const string likes = "Likes (20)";
int likesCount = int.Parse(likes.Substring(likes.IndexOf('(') + 1, (likes.Length - likes.IndexOf(')') + 1 )));

Matching when the part in paranthesis is supposed to be a number;
string inputstring="Likes (20)"
Regex reg=new Regex(#"\((\d+)\)")
string num= reg.Match(inputstring).Groups[1].Value
Explanation:
By definition regexp matches a substring, so unless you indicate otherwise the string you are looking for can occur at any place in your string.
\d stand for digits. It will match any single digit.
We want it to potentially be repeated several times, and we want at least one. The + sign is regexp for previous symbol or group repeated 1 or more times.
So \d+ will match one or more digits. It will match 20.
To insure that we get the number that is in paranteses we say that it should be between ( and ). These are special characters in regexp so we need to escape them.
(\d+) would match (20), and we are almost there.
Since we want the part inside the parantheses, and not including the parantheses we tell regexp that the digits part is a single group.
We do that by using parantheses in our regexp. ((\d+)) will still match (20), but now it will note that 20 is a subgroup of this match and we can fetch it by Match.Groups[].
For any string in parantheses things gets a little bit harder.
Regex reg=new Regex(#"\((.+)\)")
Would work for many strings. (the dot matches any character) But if the input is something like "This is an example(parantesis1)(parantesis2)", you would match (parantesis1)(parantesis2) with parantesis1)(parantesis2 as the captured subgroup. This is unlikely to be what you are after.
The solution can be to do the matching for "any character exept a closing paranthesis"
Regex reg=new Regex(#"\(([^\(]+)\)")
This will find (parantesis1) as the first match, with parantesis1 as .Groups[1].
It will still fail for nested paranthesis, but since regular expressions are not the correct tool for nested paranthesis I feel that this case is a bit out of scope.
If you know that the string always starts with "Likes " before the group then Saves solution is better.

extract last match from string in c#

i have strings in the form [abc].[some other string].[can.also.contain.periods].[our match]
i now want to match the string "our match" (i.e. without the brackets), so i played around with lookarounds and whatnot. i now get the correct match, but i don't think this is a clean solution.
(?<=\.?\[) starts with '[' or '.['
([^\[]*) our match, i couldn't find a way to not use a negated character group
`.*?` non-greedy did not work as expected with lookarounds,
it would still match from the first match
(matches might contain escaped brackets)
(?=\]$) string ends with an ]
language is .net/c#. if there is an easier solution not involving a regex i'd be also happy to know
what really irritates me is the fact, that i cannot use (.*?) to capture the string, as it seems non-greedy does not work with lookbehinds.
i also tried: Regex.Split(str, #"\]\.\[").Last().TrimEnd(']');, but i'm not really pround of this solution either

The following should do the trick. Assuming the string ends after the last match.
string input = "[abc].[some other string].[can.also.contain.periods].[our match]";
var search = new Regex("\\.\\[(.*?)\\]$", RegexOptions.RightToLeft);
string ourMatch = search.Match(input).Groups[1]);

Assuming you can guarantee the input format, and it's just the last entry you want, LastIndexOf could be used:
string input = "[abc].[some other string].[can.also.contain.periods].[our match]";
int lastBracket = input.LastIndexOf("[");
string result = input.Substring(lastBracket + 1, input.Length - lastBracket - 2);

With String.Split():
string input = "[abc].[some other string].[can.also.contain.periods].[our match]";
char[] seps = {'[',']','\\'};
string[] splitted = input.Split(seps,StringSplitOptions.RemoveEmptyEntries);
you get "out match" in splitted[7] and can.also.contain.periods is left as one string (splitted[4])
Edit: the array will have the string inside [] and then . and so on, so if you have a variable number of groups, you can use that to get the value you want (or remove the strings that are just '.')
Edited to add the backslash to the separator to treat cases like '\[abc\]'
Edit2: for nested []:
string input = #"[abc].[some other string].[can.also.contain.periods].[our [the] match]";
string[] seps2 = { "].["};
string[] splitted = input.Split(seps2, StringSplitOptions.RemoveEmptyEntries);
you our [the] match] in the last element (index 3) and you'd have to remove the extra ]

You have several options:
RegexOptions.RightToLeft - yes, .NET regex can do this! Use it!
Match the whole thing with greedy prefix, use brackets to capture the suffix that you're interested in
So generally, pattern becomes .*(pattern)
In this case, .*\[([^\]]*)\], then extract what \1 captures (see this on rubular.com)
References
regular-expressions.info/Grouping with brackets