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How to extract specific number in a string surrounded by numbers and text C#

I am trying to extract specific number in a string with a format of "Q23-00000012-A14" I only wanted to get the numbers in 8 digit 00000000 the 12.
string rx = "Q23-00000012-A14"
string numb = Regex.Replace(rx, #"\D", "");
txtResult.Text = numb;
But im getting the result of 230000001214, I only want to get the 12 and disregard the rest. Can someone guide me.

If your string are always in this format (numbers are covered with "-"), I suggest useing string.split()
string rx = "Q23-00000012-A14"
string numb = int.parse(rx.Split('-')[1]).ToString();//this will get 12 for you
txtResult.Text = numb;
It's an easier way than using regex
Edit!! When you use rx.split('-') , it break string into array of strings with value of splited texts before and after '-'
So in this case:
rx.Split('-')[0]= "Q23"
rx.Split('-')[1]= "00000012"
rx.Split('-')[2]= "A12"

So you shouldn't use Replace. Use Match instead.
string pattern = #"[A-Z]\d+-(\d+)-[A-Z]\d+" ;
var regex = new Regex(pattern);
var match = regex.Match("Q23-00000012-A14");
if (match.Success)
{
String eightNumberString = match.Groups[1].Value; // Contains "00000012"
int yourvalueAsInt = Convert.ToInt32(eightNumberString) ; // Contains 12
}

Why you use don't simply substring or split function ?
string rx = "Q23-00000012-A14";
// substring
int numb = int.Parse(rx.Substring(5, 8));
// or split
int numb = int.Parse(rx.Split('-')[1]);
txtResult.Text = numb.ToString();
(I think it's a better way to use split method because if you change your constant 'Q23' length the method still work)

replacing characters in a single field of a comma-separated list

I have string in my c# code
a,b,c,d,"e,f",g,h
I want to replace "e,f" with "e f" i.e. ',' which is inside inverted comma should be replaced by space.
I tried using string.split but it is not working for me.

OK, I can't be bothered to think of a regex approach so I am going to offer an old fashioned loop approach which will work:
string DoReplace(string input)
{
bool isInner = false;//flag to detect if we are in the inner string or not
string result = "";//result to return
foreach(char c in input)//loop each character in the input string
{
if(isInner && c == ',')//if we are in an inner string and it is a comma, append space
result += " ";
else//otherwise append the character
result += c;
if(c == '"')//if we have hit an inner quote, toggle the flag
isInner = !isInner;
}
return result;
}
NOTE: This solution assumes that there can only be one level of inner quotes, for example you cannot have "a,b,c,"d,e,"f,g",h",i,j" - because that's just plain madness!

For the scenario where you only need to match one pair of letters, the following regex will work:
string source = "a,b,c,d,\"e,f\",g,h";
string pattern = "\"([\\w]),([\\w])\"";
string replace = "\"$1 $2\"";
string result = Regex.Replace(source, pattern, replace);
Console.WriteLine(result); // a,b,c,d,"e f",g,h
Breaking apart the pattern, it is matching any instance where there is a "X,X" sequence where X is any letter, and is replacing it with the very same sequence, with a space in between the letters instead of a comma.
You could easily extend this if you needed to to have it match more than one letter, etc, as needed.
For the case where you can have multiple letters separated by commas within quotes that need to be replaced, the following can do it for you. Sample text is a,b,c,d,"e,f,a",g,h:
string source = "a,b,c,d,\"e,f,a\",g,h";
string pattern = "\"([ ,\\w]+),([ ,\\w]+)\"";
string replace = "\"$1 $2\"";
string result = source;
while (Regex.IsMatch(result, pattern)) {
result = Regex.Replace(result, pattern, replace);
}
Console.WriteLine(result); // a,b,c,d,"e f a",g,h
This does something similar compared to the first one, but just removes any comma that is sandwiched by letters surrounded by quotes, and repeats it until all cases are removed.

Here's a somewhat fragile but simple solution:
string.Join("\"", line.Split('"').Select((s, i) => i % 2 == 0 ? s : s.Replace(",", " ")))
It's fragile because it doesn't handle flavors of CSV that escape double-quotes inside double-quotes.

Use the following code:
string str = "a,b,c,d,\"e,f\",g,h";
string[] str2 = str.Split('\"');
var str3 = str2.Select(p => ((p.StartsWith(",") || p.EndsWith(",")) ? p : p.Replace(',', ' '))).ToList();
str = string.Join("", str3);

Use Split() and Join():
string input = "a,b,c,d,\"e,f\",g,h";
string[] pieces = input.Split('"');
for ( int i = 1; i < pieces.Length; i += 2 )
{
pieces[i] = string.Join(" ", pieces[i].Split(','));
}
string output = string.Join("\"", pieces);
Console.WriteLine(output);
// output: a,b,c,d,"e f",g,h

String "de-concatenation"

I have two strings like this
string s = "abcdef";
string t = "def";
I would like to remove t from s. Can I do this like this?
s = s - t?
EDIT
I will have two strings s and t, t will be an ending substring of s. I want to remove t from s.

No, but you can do this:
var newStr = "abcdef".Replace("def", "");
Per your comments, if you want to only remove the trailing pattern you can use a Regex:
var newStr = Regex.Replace("defdefdef", "(def)$", "");
The '$' will anchor to the end of the string, so it will only remove the final 'def'
Turning this into an extension method:
public static String ReplaceEnd(this string input, string subStr, string replace = "")
{
//Per Alexei Levenkov's comments, the string should
// be escaped in order to avoid accidental injection
// of special characters into the Regex pattern
var escaped = Regex.Escape(subStr);
var pattern = String.Format("({0})$", escaped);
return Regex.Replace(input, pattern, replace);
}
Using this method with your code above would become:
string s = "abcdef";
string t = "def";
s = s.ReplaceEnd(t); // Ta Da!

Like this:
if (s.EndsWith(t))
{
s = s.Substring(0, s.LastIndexOf(t));
}

s = s.Substring(0, s.Length - t.Length)
Substring takes two arguments: start and length. You want to take things from the start of abcdef, that's index 0, and you want to take all the characters minus the characters from t, which is the difference of length of the two strings.
This assumes the OP's contract of "t will be an ending substring of s". If in fact this precondition is not guaranteed, it needs if (s.EndsWith(t)) around it.

Removing unwanted characters from a string

I have a program where I take a date from an RSS file and attempt to convert it into a DateTime. Unfortunately, the RSS file that I have to use has a lot of spacing issues. When I parse the string I get this:
"\t\t\n\t\t4/13/2011\n\t\t\t\t\t\t\t\t\t\t\t\t\t\n\t\t\t\t"
I want to remove all of the \t's and\n's. So far these have all failed:
finalDateString.Trim('\t');
finalDateString.Trim('\n');
finalDateString.Trim();
finalDateString.Replace("\t", "");
finalDateString.Replace("\n", "");
finalDateString.Replace(" ", "");
Every one of the commands will return the same string. Any suggestions?
(I tagged RSS in the case that there is an RSS reason for this)

You need to assign the original value the Replace output. You do not need to do the trim either as the replace will get rid of all of them.
finalDateString = finalDateString.Replace("\t", "");
finalDateString = finalDateString.Replace("\n", "");

First, you can remove all the whitespace from your string by using a 1-character regular expression:
String finalDateTimeString = "\t\t\n\t\t4/13/2011\n\t\t\t\t\t\t\t\t\t\t\t\t\t\n\t\t\t\t";
Regex whitespaceRegex = new Regex("\\s");
finalDateTimeString = whitespaceRegex.Replace(finalDateTimeString, "");
I just tested this, and it worked.
Second, I just tested calling DateTime.Parse() on your string, and it worked without even removing the whitespace. So maybe you don't even have to do that.
String finalDateTimeString = "\t\t\n\t\t4/13/2011\n\t\t\t\t\t\t\t\t\t\t\t\t\t\n\t\t\t\t";
DateTime finalDateTime = DateTime.Parse(finalDateTimeString);
// finalDateTime.toString() == "4/13/2011 12:00:00 AM"

I will use Regular expressions
string strRegex = #"([\s])";
Regex myRegex = new Regex(strRegex);
string strTargetString = #" 4/13/2011 ";
string strReplace = "";
string result = myRegex.Replace(strTargetString, strReplace);

using Regex.Replace:
string result = Regex.Replace(data,"[\\t,\\n]",""));

All the previously posted answers remove all whitespace from the string, but it would be more robust to only remove leading and trailing whitespace.
finalDateTimeString = Regex.Replace(finalDateTimeString, #"^\s+", "");
finalDateTimeString = Regex.Replace(finalDateTimeString, #"\s+$", "");
[ I don't know C#, so I'm guessing at the syntax from the other posts. Corrections welcome. ]

private String stringclear(String str)
{
String tuslar = "qwertyuopasdfghjklizxcvbnmQWERTYUIOPASDFGHJKLZXCVBNM._0123456789 :;-+/*#%()[]!\nüÜğĞİışŞçÇöÖ"; // also you can add utf-8 chars
StringBuilder sb = new StringBuilder();
for (int i = 0; i < str.Length; i++)
{
if (tuslar.Contains(str[i].ToString())) //from tuslar string. non special chars
sb.Append(str[i]);
if (str[i] == (char)13) // special char (enter key)
sb.Append(str[i]);
}
return sb.ToString();
}

Regex removing double/triple comma in string

I need to parse a string so the result should output like that:
"abc,def,ghi,klm,nop"
But the string I am receiving could looks more like that:
",,,abc,,def,ghi,,,,,,,,,klm,,,nop"
The point is, I don't know in advance how many commas separates the words.
Is there a regex I could use in C# that could help me resolve this problem?

You can use the ,{2,} expression to match any occurrences of 2 or more commas, and then replace them with a single comma.
You'll probably need a Trim call in there too, to remove any leading or trailing commas left over from the Regex.Replace call. (It's possible that there's some way to do this with just a regex replace, but nothing springs immediately to mind.)
string goodString = Regex.Replace(badString, ",{2,}", ",").Trim(',');

Search for ,,+ and replace all with ,.
So in C# that could look like
resultString = Regex.Replace(subjectString, ",,+", ",");
,,+ means "match all occurrences of two commas or more", so single commas won't be touched. This can also be written as ,{2,}.

a simple solution without regular expressions :
string items = inputString.Split(new[] { ',' }, StringSplitOptions.RemoveEmptyEntries);
string result = String.Join(",", items);

Actually, you can do it without any Trim calls.
text = Regex.Replace(text, "^,+|,+$|(?<=,),+", "");
should do the trick.
The idea behind the regex is to only match that, which we want to remove. The first part matches any string of consecutive commas at the start of the input string, the second matches any consecutive string of commas at the end, while the last matches any consecutive string of commas that follows a comma.

Here is my effort:
//Below is the test string
string test = "YK 002 10 23 30 5 TDP_XYZ "
private static string return_with_comma(string line)
{
line = line.TrimEnd();
line = line.Replace(" ", ",");
line = Regex.Replace(line, ",,+", ",");
string[] array;
array = line.Split(',');
for (int x = 0; x < array.Length; x++)
{
line += array[x].Trim();
}
line += "\r\n";
return line;
}
string result = return_with_comma(test);
//Output is
//YK,002,10,23,30,5,TDP_XYZ