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Need to create a Regular expression to Split String after first \r\n

I have been stuck in a situation .
Here are few input strings -
"abacuses\r\n25"
"alphabet\r\n56,\r\n57"
"animals\r\n44,\r\n45,\r\n47"
I need the output to be splited like -
"abacuses\r\n25" to be splitted into A)abacuses B)25
"alphabet\r\n56,\r\n57" to be splitted into A)alphabet B)56,57
"animals\r\n44,\r\n45,\r\n47" to be splitted into A)animals B)44,45,47
So far I have tried this but it doesn't work-
string[] ina = Regex.Split(indexname, #"\r\n\D+");
string[] ina = Regex.Split(indexname, #"\r\n\");
Please Help

No regex needed in your example. You basicaly parse string:
string input = "animals\r\n44,\r\n45,\r\n47";
var split = input.Split(new char[]{'\r','\n',','}, StringSplitOptions.RemoveEmptyEntries);
var name = split[0]; //animals
var args = string.Join(",", split.Skip(1)); //44,45,37
Many people use it for parsing, but Regex is not a parsing language! It is pattern matcher! It is used to find substrings in string! If you can just Split your string - just do it, really. It is much easier to understand than Regex expression.

If you need to split a string at the first \r\n, you may use a String.Split with a count argument:
var line = "animals\r\n44,\r\n45,\r\n47";
var res = line
.Split(new[] {"\r\n"}, 2, StringSplitOptions.RemoveEmptyEntries);
// Demo output
Console.WriteLine(res[0]);
if (res.GetLength(0) > 1)
Console.WriteLine(res[1].Replace("\r\n", "")); // In the second value, linebreaks should be removed
See the C# demo
The 2 in .Split(new[] {"\r\n"}, 2, StringSplitOptions.RemoveEmptyEntries) means that the whole string should be split into 2 parts only and since the string is processed from left to right, the split will occur on the first "\r\n" substring found.

Remove characters between different parameters [duplicate]

This question already has an answer here:
Learning Regular Expressions [closed]
(1 answer)
Closed 7 years ago.
I have a string of different emails
ex: "email1#uy.com, email2#iu.it, email3#uu.edu" etc, etc
I would like to formulate a Regex that creates the following output
ex: "email1,email2,email3" etc, etc
How can I remove characters between an "#" and "," but leaving a "," and a Space in C#
Thank you so much for the help!!

If you want to replace all characters between # and comma by blank, the easiest option is to use Regex.Replace:
var emails = "a#m.com, b#m.com, d#m.com";
var result = Regex.Replace(emails, "#[^,]+", string.Empty);
// result is "a, b, d"
Please note that it leaves spaces after comma in the result, as you wanted in your question, though your example result has spaces removed.
The regular expression looks for all substrings starting '#' characters, followed by any character which is not comma. Those substrings are replaced with empty string.

Replacing all occurrences of #[^,]+ with an empty string will do the job.
The expression matches sequences that start in #, inclusive, up to a comma or to the end, exclusive. Therefore, commas in the original string of e-mails would be kept.
Demo.

Maybe you don't need to use a regex, in that case you can do the following:
string input = "email1#uy.com, email2#iu.it, email3#uu.edu";
input = input.Replace(" ", "");
string[] ocurrences = input.Split(',');
for (int i = 0; i < ocurrences.Length; i++)
{
string s = ocurrences[i];
ocurrences[i] = s.Substring(0, s.IndexOf('#'));
}
string final = string.Join(", ", occurences);

What's the best way to merge strings?

Let's say I have a foreach-loop with strings like this:
String newStr='';
String str='a b c d e';
foreach(String strChar in str.split(' ')) {
newStr+=strChar+',';
}
the result would be something like: a,b,c,d,e, but what I want is a,b,c,d,e without the last comma. I normally split the last comma out but this seems ugly and overweight. Is there any lightweight way to do this?
Additional to this question: Is there any easy solution to add an "and" to the constellation that the result is something like: a, b, c, d and e for user output?
p.s.: I know that I can use the replace-method in the example but this is not what I'm looking because in most cases you can't use it (for example when you build a sql string).

I would use string.Join:
string newStr = string.Join(",", str.Split(' '));
Alternatively, you could add the separator at the start of the body of the loop, but not on the first time round.
I'd suggest using StringBuilder if you want to keep doing this by hand though. In fact, with a StringBuilder you could just unconditionally append the separator, and then decrement the length at the end to trim that end.
You also wrote:
for example when you build a sql string
It's very rarely a good idea to build a SQL string like this. In particular, you should absolutely not use strings from user input here - use parameterized SQL instead. Building SQL is typically the domain of ORM code... in which case it's usually better to use an existing ORM than to roll your own :)

you're characterizing the problem as appending a comma after every string except the last. Consider characterizing it as prepending a comma before every string but the first. It's an easier problem.
As for your harder version there are several dozen solutions on my blog and in this question.
Eric Lippert's challenge "comma-quibbling", best answer?

string.Join may be your friend:
String str='a b c d e';
var newStr = string.Join(",", str.Split(' '));

Here's how you can do it where you have "and" before the last value.
var vals = str.Split(' ');
var ans = vals.Length == 1 ?
str :
string.Join(", ", vals.Take(vals.Length - 1))) + ", and " + vals.Last();

newStr = String.Join(",", str.split(' '));

You can use Regex and replace whitespaces with commas
string newst = Regex.Replace(input, " ", ",");

First, you should be using a StringBuilder for string manipulations of this sort. Second, it's just an if conditional on the insert.
System.Text.StringBuilder newStr = new System.Text.StringBuilder("");
string oldStr = "a b c d e";
foreach(string c in oldStr.Split(' ')) {
if (newStr.Length > 0) newStr.Append(",");
newStr.Append(c);
}

String.Split cut separator

Is it possible to use String.Split without cutting separator from string?
For example I have string
convertSource = "http://www.domain.com http://www.domain1.com";
I want to build array and use code below
convertSource.Split(new[] { " http" }, StringSplitOptions.RemoveEmptyEntries)
I get such array
[1] http://www.domain.com
[2] ://www.domain1.com
I would like to keep http, it seems String.Split not only separate string but also cut off separator.

This is screaming for Regular Expressions:
Regex regEx = new Regex(#"((mailto\:|(news|(ht|f)tp(s?))\://){1}\S+)");
Match match= regEx.Match("http://www.domain.com http://www.domain1.com");
IList<string> values = new List<string>();
while (match.Success)
{
values.Add(match.Value);
match = match.NextMatch();
}

string[] array = Regex.Split(convertSource, #"(?=http://)");

That's because you use " http" as separator.
Try this:
string separator = " ";
convertSource.Split(separator.ToCharArray(), StringSplitOptions.RemoveEmptyEntries)
The Split method works in a way that when it comes to the separator you provide it cuts it off right there and removes the separator from the string also.
From what you are saying you want to do there are other ways to split the string keeping the delimiters and then if you only want to remove leading or trailing spaces from your string then I wouuld suggest that you use .Trim() method: convertSource.Trim()

How to remove leading and trailing spaces from a string

I have the following input:
string txt = " i am a string "
I want to remove space from start of starting and end from a string.
The result should be: "i am a string"
How can I do this in c#?

String.Trim
Removes all leading and trailing white-space characters from the current String object.
Usage:
txt = txt.Trim();
If this isn't working then it highly likely that the "spaces" aren't spaces but some other non printing or white space character, possibly tabs. In this case you need to use the String.Trim method which takes an array of characters:
char[] charsToTrim = { ' ', '\t' };
string result = txt.Trim(charsToTrim);
Source
You can add to this list as and when you come across more space like characters that are in your input data. Storing this list of characters in your database or configuration file would also mean that you don't have to rebuild your application each time you come across a new character to check for.
NOTE
As of .NET 4 .Trim() removes any character that Char.IsWhiteSpace returns true for so it should work for most cases you come across. Given this, it's probably not a good idea to replace this call with the one that takes a list of characters you have to maintain.
It would be better to call the default .Trim() and then call the method with your list of characters.

You can use:
String.TrimStart - Removes all leading occurrences of a set of characters specified in an array from the current String object.
String.TrimEnd - Removes all trailing occurrences of a set of characters specified in an array from the current String object.
String.Trim - combination of the two functions above
Usage:
string txt = " i am a string ";
char[] charsToTrim = { ' ' };
txt = txt.Trim(charsToTrim)); // txt = "i am a string"
EDIT:
txt = txt.Replace(" ", ""); // txt = "iamastring"

I really don't understand some of the hoops the other answers are jumping through.
var myString = " this is my String ";
var newstring = myString.Trim(); // results in "this is my String"
var noSpaceString = myString.Replace(" ", ""); // results in "thisismyString";
It's not rocket science.

txt = txt.Trim();

Or you can split your string to string array, splitting by space and then add every item of string array to empty string.
May be this is not the best and fastest method, but you can try, if other answer aren't what you whant.

text.Trim() is to be used
string txt = " i am a string ";
txt = txt.Trim();

Use the Trim method.

static void Main()
{
// A.
// Example strings with multiple whitespaces.
string s1 = "He saw a cute\tdog.";
string s2 = "There\n\twas another sentence.";
// B.
// Create the Regex.
Regex r = new Regex(#"\s+");
// C.
// Strip multiple spaces.
string s3 = r.Replace(s1, #" ");
Console.WriteLine(s3);
// D.
// Strip multiple spaces.
string s4 = r.Replace(s2, #" ");
Console.WriteLine(s4);
Console.ReadLine();
}
OUTPUT:
He saw a cute dog.
There was another sentence.
He saw a cute dog.

You Can Use
string txt = " i am a string ";
txt = txt.TrimStart().TrimEnd();
Output is "i am a string"