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Match Characters after last dot in string

I have a string and I want to get the words after the last dot in the string.
Example:
input string = "XimEngine.DynamicGui.PickKind.DropDown";
Result:
DropDown

There's no need in Regex, let's find out the last . and get Substring:
string result = input.Substring(input.LastIndexOf('.') + 1);
If input doesn't have . the entire input will be returned

Not a RegEx answer, but you could do:
var result = input.Split('.').Last();

In Regex you can tell the parser to work from the end of the string/buffer by specifying the option RightToLeft.
By using that we can just specify a forward pattern to find a period (\.) and then capture (using ( )) our text we are interested into group 1 ((\w+)).
var str = "XimEngine.DynamicGui.PickKind.DropDown";
Console.WriteLine(Regex.Match(str,
#"\.(\w+)",
RegexOptions.RightToLeft).Groups[1].Value);
Outputs to console:
DropDown
By working from the other end of the string means we don't have to deal with anything at the beginning of the string to where we need to extract text.

Extract value from a string in C# from a specific position

I have bunch of files in a folder and I am looping through them.
How do I extract the value from the below example? I need the value 0519 only.
DOC 75-20-0519-1.PDF
The below code gives the complete part include -1.
Convert.ToInt32(Path.GetFileNameWithoutExtension(objFile).Split('-')[2]);
Appreciate any help.

You can try regular expressions in order to match the value.
pattern:
[0-9]+ - one ore more digits
(?=[^0-9][0-9]+$) - followed by not a digit and one or more digits and end of string
code:
using System.Text.RegularExpressions;
...
string file = "DOC 75-20-0519-1.PDF";
// "0519"
string result = Regex
.Match(Path.GetFileNameWithoutExtension(file), #"[0-9]+(?=[^0-9][0-9]+$)")
.Value;
If Split('-') fails, and you have an entire string as a result, it seems that you have a wrong delimiter. It can be, say, one of the dashes:
"DOC 75–20–0519–1.PDF"; // n-dash
"DOC 75—20—0519—1.PDF"; // m-dash

You can use REGEX for this
Match match = Regex.Match("DOC 75-20-0519-1.PDF", #"DOC\s+\d+\-\d+\-(\d+)\-\d+", RegexOptions.IgnoreCase);
string data = match.Groups[1].Value;

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();

Extracting only the substring containing letters from a string containing digits strings and symbols

I have a string that is like the following:
string str = hello_16_0_2016;
What I want is to extract hello from the string. As in my program the string part can occur anywhere as it is autogenerated, so I cannot fix the position of my string.
For example: I can take the first five string from above and store it in a new variable.
But as occurring of letters is random and I want to extract only letters from the string above, so can someone guide me to the correct procedure to do this?

Could you just use a simple regular expression to pull out only alphabetic characters, assuming you only need a-z?
using System.Text.RegularExpressions;
var str = "hello_16_0_2016";
var onlyLetters = Regex.Replace(str, #"[^a-zA-Z]", "");
// onlyLetters = "hello"

I'd use something like this (uses Linq):
var str = "hello_16_0_2016";
var result = string.Concat(str.Where(char.IsLetter));
Check it out
Or, if performance is a concern (because you have to do this on a tight loop, or have to convert hundreds of thousands of strings), it'd probably be faster to do:
var result = new string(str.Where(char.IsLetter).ToArray());
Check it too

But as occurring of letters is random and I want to extract only
letters from the string above, so can someone guide me to the correct
procedure to do this?
The following will extract the first text, without numbers anywhere in the string:
Console.WriteLine( Regex.Match("hello_16_0_2016", #"[A-Za-z]+").Value ); // "hello"

Using Regex to match quoted string with embedded, non-escaped quotes

I am trying to match a string in the following pattern with a regex.
string text = "'Emma','The Last Leaf','Gulliver's travels'";
string pattern = #"'(.*?)',?";
foreach (Match match in Regex.Matches(text,pattern,RegexOptions.IgnoreCase))
{
Console.WriteLine(match + " " + match.Index);
Console.WriteLine(match.Groups[1].Captures[0]);
}
This matches "Emma" and "The Last leaf" correctly, however the third match is "Gulliver". But the desired match is "Gulliver's travels". How can I build a regex for a patterns like this?

Since , is your delimiter, you can try changing your pattern like this. It should work.
string pattern = #"'(.*?)'(?:,|$)";
The way this works is, it looks for a single quote followed by a comma or end of the line.

I think this can work '(.*?)',|'(.*)' as regular expression.

you may consider to use look behind /look ahead:
"(?<=^'|',').*?(?='$|',')"
test with grep:
kent$ echo "'Emma','The Last Leaf','Gulliver's travels'"|grep -Po "(?<=^'|',').*?(?='$|',')"
Emma
The Last Leaf
Gulliver's travels

You can't, if you have single-quote delimited strings and Gulliver's contains a single, unescaped quote there's no way to distinguish it from the end of a string. You could always just split it by commas and trim 's from either side but I'm not sure that's what you want:
string text = "'Emma','The Last Leaf','Gulliver's travels'";
foreach(string s in text.split(new char[] {','})) {
Console.WriteLine(s.Trim('\''));
}