How to split a string on the nth occurrence? - c#

What I want to do is to split on the nth occurrence of a string (in this case it's "\t"). This is the code I'm currently using and it splits on every occurrence of "\t".
string[] items = input.Split(new char[] {'\t'}, StringSplitOptions.RemoveEmptyEntries);
If input = "one\ttwo\tthree\tfour", my code returns the array of:
one
two
three
four
But let's say I want to split it on every "\t" after the second "\t". So, it should return:
one two
three
four


There is nothing built in.
You can use the existing Split, use Take and Skip with string.Join to rebuild the parts that you originally had.
string[] items = input.Split(new char[] {'\t'},
StringSplitOptions.RemoveEmptyEntries);
string firstPart = string.Join("\t", items.Take(nthOccurrence));
string secondPart = string.Join("\t", items.Skip(nthOccurrence))
string[] everythingSplitAfterNthOccurence = items.Skip(nthOccurrence).ToArray();
An alternative is to iterate over all the characters in the string, find the index of the nth occurrence and substring before and after it (or find the next index after the nth, substring on that etc... etc... etc...).


[EDIT] After re-reading the edited OP, I realise this doesn't do what is now asked. This will split on every nth target; the OP wants to split on every target AFTER the nth one.
I'll leave this here for posterity anyway.
If you were using the MoreLinq extensions you could take advantage of its Batch method.
Your code would then look like this:
string text = "1\t2\t3\t4\t5\t6\t7\t8\t9\t10\t11\t12\t13\t14\t15\t16\t17";
var splits = text.Split('\t').Batch(5);
foreach (var split in splits)
Console.WriteLine(string.Join("", split));
I'd probably just use Oded's implementation, but I thought I'd post this for an alternative approach.
The implementation of Batch() looks like this:
public static class EnumerableExt
{
public static IEnumerable<IEnumerable<TSource>> Batch<TSource>(this IEnumerable<TSource> source, int size)
{
TSource[] bucket = null;
var count = 0;
foreach (var item in source)
{
if (bucket == null)
bucket = new TSource[size];
bucket[count++] = item;
if (count != size)
continue;
yield return bucket;
bucket = null;
count = 0;
}
if (bucket != null && count > 0)
yield return bucket.Take(count);
}
}


It is likely that you will have to split and re-combine. Something like
int tabIndexToRemove = 3;
string str = "My\tstring\twith\tloads\tof\ttabs";
string[] strArr = str.Split('\t');
int numOfTabs = strArr.Length - 1;
if (tabIndexToRemove > numOfTabs)
throw new IndexOutOfRangeException();
str = String.Empty;
for (int i = 0; i < strArr.Length; i++)
str += i == tabIndexToRemove - 1 ?
strArr[i] : String.Format("{0}\t", strArr[i]);
Result:
My string withloads of tabs
I hope this helps.


// Return a substring of str upto but not including
// the nth occurence of substr
function getNth(str, substr, n) {
var idx;
var i = 0;
var newstr = '';
do {
idx = s.indexOf(c);
newstr += str.substring(0, idx);
str = str.substring(idx+1);
} while (++i < n && (newstr += substr))
return newstr;
}

Related

How to stop String.Concat(); from removing whitespaces? [duplicate]

I would like to split a string with delimiters but keep the delimiters in the result.
How would I do this in C#?

If the split chars were ,, ., and ;, I'd try:
using System.Text.RegularExpressions;
...
string[] parts = Regex.Split(originalString, #"(?<=[.,;])")
(?<=PATTERN) is positive look-behind for PATTERN. It should match at any place where the preceding text fits PATTERN so there should be a match (and a split) after each occurrence of any of the characters.

If you want the delimiter to be its "own split", you can use Regex.Split e.g.:
string input = "plum-pear";
string pattern = "(-)";
string[] substrings = Regex.Split(input, pattern); // Split on hyphens
foreach (string match in substrings)
{
Console.WriteLine("'{0}'", match);
}
// The method writes the following to the console:
// 'plum'
// '-'
// 'pear'
So if you are looking for splitting a mathematical formula, you can use the following Regex
#"([*()\^\/]|(?<!E)[\+\-])"
This will ensure you can also use constants like 1E-02 and avoid having them split into 1E, - and 02
So:
Regex.Split("10E-02*x+sin(x)^2", #"([*()\^\/]|(?<!E)[\+\-])")
Yields:
10E-02
*
x
+
sin
(
x
)
^
2

Building off from BFree's answer, I had the same goal, but I wanted to split on an array of characters similar to the original Split method, and I also have multiple splits per string:
public static IEnumerable<string> SplitAndKeep(this string s, char[] delims)
{
int start = 0, index;
while ((index = s.IndexOfAny(delims, start)) != -1)
{
if(index-start > 0)
yield return s.Substring(start, index - start);
yield return s.Substring(index, 1);
start = index + 1;
}
if (start < s.Length)
{
yield return s.Substring(start);
}
}

Just in case anyone wants this answer aswell...
Instead of string[] parts = Regex.Split(originalString, #"(?<=[.,;])") you could use string[] parts = Regex.Split(originalString, #"(?=yourmatch)") where yourmatch is whatever your separator is.
Supposing the original string was
777- cat
777 - dog
777 - mouse
777 - rat
777 - wolf
Regex.Split(originalString, #"(?=777)") would return
777 - cat
777 - dog
and so on

This version does not use LINQ or Regex and so it's probably relatively efficient. I think it might be easier to use than the Regex because you don't have to worry about escaping special delimiters. It returns an IList<string> which is more efficient than always converting to an array. It's an extension method, which is convenient. You can pass in the delimiters as either an array or as multiple parameters.
/// <summary>
/// Splits the given string into a list of substrings, while outputting the splitting
/// delimiters (each in its own string) as well. It's just like String.Split() except
/// the delimiters are preserved. No empty strings are output.</summary>
/// <param name="s">String to parse. Can be null or empty.</param>
/// <param name="delimiters">The delimiting characters. Can be an empty array.</param>
/// <returns></returns>
public static IList<string> SplitAndKeepDelimiters(this string s, params char[] delimiters)
{
var parts = new List<string>();
if (!string.IsNullOrEmpty(s))
{
int iFirst = 0;
do
{
int iLast = s.IndexOfAny(delimiters, iFirst);
if (iLast >= 0)
{
if (iLast > iFirst)
parts.Add(s.Substring(iFirst, iLast - iFirst)); //part before the delimiter
parts.Add(new string(s[iLast], 1));//the delimiter
iFirst = iLast + 1;
continue;
}
//No delimiters were found, but at least one character remains. Add the rest and stop.
parts.Add(s.Substring(iFirst, s.Length - iFirst));
break;
} while (iFirst < s.Length);
}
return parts;
}
Some unit tests:
text = "[a link|http://www.google.com]";
result = text.SplitAndKeepDelimiters('[', '|', ']');
Assert.IsTrue(result.Count == 5);
Assert.AreEqual(result[0], "[");
Assert.AreEqual(result[1], "a link");
Assert.AreEqual(result[2], "|");
Assert.AreEqual(result[3], "http://www.google.com");
Assert.AreEqual(result[4], "]");

A lot of answers to this! One I knocked up to split by various strings (the original answer caters for just characters i.e. length of 1). This hasn't been fully tested.
public static IEnumerable<string> SplitAndKeep(string s, params string[] delims)
{
var rows = new List<string>() { s };
foreach (string delim in delims)//delimiter counter
{
for (int i = 0; i < rows.Count; i++)//row counter
{
int index = rows[i].IndexOf(delim);
if (index > -1
&& rows[i].Length > index + 1)
{
string leftPart = rows[i].Substring(0, index + delim.Length);
string rightPart = rows[i].Substring(index + delim.Length);
rows[i] = leftPart;
rows.Insert(i + 1, rightPart);
}
}
}
return rows;
}

This seems to work, but its not been tested much.
public static string[] SplitAndKeepSeparators(string value, char[] separators, StringSplitOptions splitOptions)
{
List<string> splitValues = new List<string>();
int itemStart = 0;
for (int pos = 0; pos < value.Length; pos++)
{
for (int sepIndex = 0; sepIndex < separators.Length; sepIndex++)
{
if (separators[sepIndex] == value[pos])
{
// add the section of string before the separator
// (unless its empty and we are discarding empty sections)
if (itemStart != pos || splitOptions == StringSplitOptions.None)
{
splitValues.Add(value.Substring(itemStart, pos - itemStart));
}
itemStart = pos + 1;
// add the separator
splitValues.Add(separators[sepIndex].ToString());
break;
}
}
}
// add anything after the final separator
// (unless its empty and we are discarding empty sections)
if (itemStart != value.Length || splitOptions == StringSplitOptions.None)
{
splitValues.Add(value.Substring(itemStart, value.Length - itemStart));
}
return splitValues.ToArray();
}

Recently I wrote an extension method do to this:
public static class StringExtensions
{
public static IEnumerable<string> SplitAndKeep(this string s, string seperator)
{
string[] obj = s.Split(new string[] { seperator }, StringSplitOptions.None);
for (int i = 0; i < obj.Length; i++)
{
string result = i == obj.Length - 1 ? obj[i] : obj[i] + seperator;
yield return result;
}
}
}

I'd say the easiest way to accomplish this (except for the argument Hans Kesting brought up) is to split the string the regular way, then iterate over the array and add the delimiter to every element but the last.

To avoid adding character to new line try this :
string[] substrings = Regex.Split(input,#"(?<=[-])");

result = originalString.Split(separator);
for(int i = 0; i < result.Length - 1; i++)
result[i] += separator;
(EDIT - this is a bad answer - I misread his question and didn't see that he was splitting by multiple characters.)
(EDIT - a correct LINQ version is awkward, since the separator shouldn't get concatenated onto the final string in the split array.)

Iterate through the string character by character (which is what regex does anyway.
When you find a splitter, then spin off a substring.
pseudo code
int hold, counter;
List<String> afterSplit;
string toSplit
for(hold = 0, counter = 0; counter < toSplit.Length; counter++)
{
if(toSplit[counter] = /*split charaters*/)
{
afterSplit.Add(toSplit.Substring(hold, counter));
hold = counter;
}
}
That's sort of C# but not really. Obviously, choose the appropriate function names.
Also, I think there might be an off-by-1 error in there.
But that will do what you're asking.

veggerby's answer modified to
have no string items in the list
have fixed string as delimiter like "ab" instead of single character
var delimiter = "ab";
var text = "ab33ab9ab"
var parts = Regex.Split(text, $#"({Regex.Escape(delimiter)})")
.Where(p => p != string.Empty)
.ToList();
// parts = "ab", "33", "ab", "9", "ab"
The Regex.Escape() is there just in case your delimiter contains characters which regex interprets as special pattern commands (like *, () and thus have to be escaped.

using System.Collections.Generic;
using System.Text.RegularExpressions;
namespace ConsoleApplication9
{
class Program
{
static void Main(string[] args)
{
string input = #"This;is:a.test";
char sep0 = ';', sep1 = ':', sep2 = '.';
string pattern = string.Format("[{0}{1}{2}]|[^{0}{1}{2}]+", sep0, sep1, sep2);
Regex regex = new Regex(pattern);
MatchCollection matches = regex.Matches(input);
List<string> parts=new List<string>();
foreach (Match match in matches)
{
parts.Add(match.ToString());
}
}
}
}

I wanted to do a multiline string like this but needed to keep the line breaks so I did this
string x =
#"line 1 {0}
line 2 {1}
";
foreach(var line in string.Format(x, "one", "two")
.Split("\n")
.Select(x => x.Contains('\r') ? x + '\n' : x)
.AsEnumerable()
) {
Console.Write(line);
}
yields
line 1 one
line 2 two

I came across same problem but with multiple delimiters. Here's my solution:
public static string[] SplitLeft(this string #this, char[] delimiters, int count)
{
var splits = new List<string>();
int next = -1;
while (splits.Count + 1 < count && (next = #this.IndexOfAny(delimiters, next + 1)) >= 0)
{
splits.Add(#this.Substring(0, next));
#this = new string(#this.Skip(next).ToArray());
}
splits.Add(#this);
return splits.ToArray();
}
Sample with separating CamelCase variable names:
var variableSplit = variableName.SplitLeft(
Enumerable.Range('A', 26).Select(i => (char)i).ToArray());

I wrote this code to split and keep delimiters:
private static string[] SplitKeepDelimiters(string toSplit, char[] delimiters, StringSplitOptions splitOptions = StringSplitOptions.None)
{
var tokens = new List<string>();
int idx = 0;
for (int i = 0; i < toSplit.Length; ++i)
{
if (delimiters.Contains(toSplit[i]))
{
tokens.Add(toSplit.Substring(idx, i - idx)); // token found
tokens.Add(toSplit[i].ToString()); // delimiter
idx = i + 1; // start idx for the next token
}
}
// last token
tokens.Add(toSplit.Substring(idx));
if (splitOptions == StringSplitOptions.RemoveEmptyEntries)
{
tokens = tokens.Where(token => token.Length > 0).ToList();
}
return tokens.ToArray();
}
Usage example:
string toSplit = "AAA,BBB,CCC;DD;,EE,";
char[] delimiters = new char[] {',', ';'};
string[] tokens = SplitKeepDelimiters(toSplit, delimiters, StringSplitOptions.RemoveEmptyEntries);
foreach (var token in tokens)
{
Console.WriteLine(token);
}

Split string after specific character or after max length

i want to split a string the following way:
string s = "012345678x0123x01234567890123456789";
s.SplitString("x",10);
should be split into
012345678
x0123
x012345678
9012345678
9
e.g. the inputstring should be split after the character "x" or length 10 - what comes first.
here is what i've tried so far:
public static IEnumerable<string> SplitString(this string sInput, string search, int maxlength)
{
int index = Math.Min(sInput.IndexOf(search), maxlength);
int start = 0;
while (index != -1)
{
yield return sInput.Substring(start, index-start);
start = index;
index = Math.Min(sInput.IndexOf(search,start), maxlength);
}
}

I would go with this regular expression:
([^x]{1,10})|(x[^x]{1,9})
which means:
Match at most 10 characters that are not x OR match x followed by at most 9 characters thar are not x
Here is working example:
string regex = "([^x]{1,10})|(x[^x]{1,9})";
string input = "012345678x0123x01234567890123456789";
var results = Regex.Matches(input, regex)
.Cast<Match>()
.Select(m => m.Value);
which produces values by you.

Personally I don't like RegEx. It creates code that is hard to de-bug and is very hard to work out what it is meant to be doing when you first look at it. So for a more lengthy solution I would go with something like this.
public static IEnumerable<string> SplitString(this string sInput, char search, int maxlength)
{
var result = new List<string>();
var count = 0;
var lastSplit = 0;
foreach (char c in sInput)
{
if (c == search || count - lastSplit == maxlength)
{
result.Add(sInput.Substring(lastSplit, count - lastSplit));
lastSplit = count;
}
count ++;
}
result.Add(sInput.Substring(lastSplit, count - lastSplit));
return result;
}
Note I changed the first parameter to a char (from a string). This code can probably be optimised some more, but it is nice and readable, which for me is more important.

Split a long string to a customized string

Hello I have a long string. I want to split it as some kind of format that has many return carrages.
Each line has 5 short words.
Ex.
string input="'250.0','250.00','250.01','250.02','250.03','250.1','250.10','250.11','250.12','250.13','250.2','250.20','250.21','250.22','250.23','250.3','250.30','250.31','250.32','250.33','250.4','250.40','250.41','250.42','250.43','250.5','250.50','250.51','250.52','250.53','250.6','250.60','250.61','250.62','250.63','250.7','250.70','250.71','250.72','250.73','250.8','250.80','250.81','250.82','250.83','250.9','250.90','250.91','250.92','250.93','357.2','357.20','362.01','362.02','362.03','362.04','362.05','362.06','362.07','366.41','648.0','648.00','648.01','648.02','648.03','648.04'";
It has 66 short words.
string output = "'250.0','250.00','250.01','250.02','250.03',
'250.1','250.10','250.11','250.12','250.13',
'250.2','250.20','250.21','250.22','250.23',
'250.3','250.30','250.31','250.32','250.33',
'250.4','250.40','250.41','250.42','250.43',
'250.5','250.50','250.51','250.52','250.53',
'250.6','250.60','250.61','250.62','250.63',
'250.7','250.70','250.71','250.72','250.73',
'250.8','250.80','250.81','250.82','250.83',
'250.9','250.90','250.91','250.92','250.93',
'357.2','357.20','362.01','362.02','362.03',
'362.04','362.05','362.06','362.07','366.41',
'648.0','648.00','648.01','648.02','648.03',
'648.04'";
I thought that I have to count char ',' in the string first such as in the example. But it could be kind of clumsy.
Thanks for advice.

If i've understood you correctly you want to
split those words by comma
group the result into lines where each line contains 5 words
build a string with Environment.NewLine as separator
string input = "'250.0','250.00','250.01','250.02','250.03','250.1','250.10','250.11','250.12','250.13','250.2','250.20','250.21','250.22','250.23','250.3','250.30','250.31','250.32','250.33','250.4','250.40','250.41','250.42','250.43','250.5','250.50','250.51','250.52','250.53','250.6','250.60','250.61','250.62','250.63','250.7','250.70','250.71','250.72','250.73','250.8','250.80','250.81','250.82','250.83','250.9','250.90','250.91','250.92','250.93','357.2','357.20','362.01','362.02','362.03','362.04','362.05','362.06','362.07','366.41','648.0','648.00','648.01','648.02','648.03','648.04'";
int groupCount = 5;
var linesGroups = input.Split(',')
.Select((s, index) => new { str = s, Position = index / groupCount, Index = index })
.GroupBy(x => x.Position);
StringBuilder outputBuilder = new StringBuilder();
foreach (var grp in linesGroups)
{
outputBuilder.AppendLine(String.Join(",", grp.Select(x => x.str)));
}
String output = outputBuilder.ToString();
Edit: The result is:
'250.0','250.00','250.01','250.02','250.03'
'250.1','250.10','250.11','250.12','250.13'
'250.2','250.20','250.21','250.22','250.23'
'250.3','250.30','250.31','250.32','250.33'
'250.4','250.40','250.41','250.42','250.43'
'250.5','250.50','250.51','250.52','250.53'
'250.6','250.60','250.61','250.62','250.63'
'250.7','250.70','250.71','250.72','250.73'
'250.8','250.80','250.81','250.82','250.83'
'250.9','250.90','250.91','250.92','250.93'
'357.2','357.20','362.01','362.02','362.03'
'362.04','362.05','362.06','362.07','366.41'
'648.0','648.00','648.01','648.02','648.03'
'648.04'
If you want to append every line with a comma(like in your example):
foreach (var grp in linesGroups)
{
outputBuilder.AppendLine(String.Join(",", grp.Select(x => x.str)) + ",");
}
// remove last comma + Environment.NewLine
outputBuilder.Length -= ( 1 + Environment.NewLine.Length );

How about this solution:
private static IEnumerable<string> SplitLongString(string input, char separator, int groupSize)
{
int indexCurrent = 0;
int indexLastOccurence = 0;
int separatorCounter = 0;
foreach (var character in input)
{
indexCurrent++;
if (character == separator)
{
separatorCounter++;
if (separatorCounter % groupSize == 0)
{
yield return input.Substring(indexLastOccurence, indexCurrent - indexLastOccurence);
indexLastOccurence = indexCurrent;
}
}
}
if (indexCurrent != indexLastOccurence)
{
yield return input.Substring(indexLastOccurence, indexCurrent - indexLastOccurence);
}
}
And you would call it:
var result = SplitLongString(input, ',', 5);
foreach (var row in result)
{
Console.WriteLine(row);
}

The simplest way would be to follow the approach from #Tim's deleted (edit: not deleted any more) answer:
Split the string into parts by comma (using string.Split)
Rearrange the obtained parts in any way you need: for example, packing by 5 in a line.
Something like that (not tested):
Console.WriteLine("string output =");
var parts = sourceString.Split(',');
int i = 0;
for (; i < parts.Length; i++)
{
if (i % 5 == 0)
Console.Write(' "');
Console.Write(parts[i]);
Console.Write(',');
if (i % 5 == 4 && i != parts.Length - 1)
Console.WriteLine('" +');
}
Console.WriteLine('";');

var input="'250.0','250.00','250.01','250.02','250.03','250.1','250.10','250.11','250.12','250.13','250.2','250.20','250.21','250.22','250.23','250.3','250.30','250.31','250.32','250.33','250.4','250.40','250.41','250.42','250.43','250.5','250.50','250.51','250.52','250.53','250.6','250.60','250.61','250.62','250.63','250.7','250.70','250.71','250.72','250.73','250.8','250.80','250.81','250.82','250.83','250.9','250.90','250.91','250.92','250.93','357.2','357.20','362.01','362.02','362.03','362.04','362.05','362.06','362.07','366.41','648.0','648.00','648.01','648.02','648.03','648.04'";
var wordsArray = input.Split(',');
var sbOutput = new StringBuilder();
for (int i = 1; i < wordsArray.Length +1; i++)
{
sbOutput.AppendFormat("{0},", wordsArray[i-1]);
if(i % 5 == 0)
sbOutput.AppendLine();
}
var output = sbOutput.ToString();

Do something like this:
string[] words = input.Split(',');
int wordsInString = words.Length;

Split large string into smaller chunks in c#

I have a large string separated by newline character. This string contains 100 lines. I want to split these line into small chunks say chunk of 20 also based on newline character.
Let's say the string variable is like this,
Line1 This is line2 Line3 is here I am Line4
Now I want to split this large string variable into small chunks of 2. The result should be 2 strings as,
Line1 This is line2
Line3 is here I am Line4
Using Split function, I am not getting the expected results. Please help me in achieving this.
Thanks in advance,
Vijay

The simple approach (Split on Environment.NewLine, then loop and append):
public static List<string> GetStringSegments(string originalString, int linesPerSegment)
{
List<string> segments = new List<string>();
string[] allLines = originalString.Split(new string[] {Environment.NewLine}, StringSplitOptions.RemoveEmptyEntries);
StringBuilder sb = new StringBuilder();
int linesProcessed = 0;
for (int i = 0; i < allLines.Length; i++)
{
sb.AppendLine(allLines[i]);
linesProcessed++;
if (linesProcessed == linesPerSegment
|| i == allLines.Length-1)
{
segments.Add(sb.ToString());
sb.Clear();
inesProcessed = 0;
}
}
return segments;
}
The above approach is slightly inefficient since it requires splitting the string first into individual lines, which creates unnecessary strings. A string of 1000 lines will create an array of 1000 strings. We can improved this if we just scan the string and search for \n:
public static List<string> GetStringSegments(string original, int linesPerSegment)
{
List<string> segments = new List<string>();
int startIndex = 0;
int newLinesEncountered = 0;
for (int i = 0; i < original.Length; i++)
{
if (original[i] == '\n')
{
newLinesEncountered++;
}
if (newLinesEncountered == linesPerSegment
|| i == original.Length - 1)
{
segments.Add(original.Substring(startIndex, (i - startIndex + 1)));
startIndex = i + 1;
newLinesEncountered = 0;
}
}
return segments;
}

You can use something like the batch operator from http://www.make-awesome.com/2010/08/batch-or-partition-a-collection-with-linq
string s = "[YOUR DATA]";
var lines = s.Split(new[]{Environment.NewLine}, StringSplitOptions.RemoveEmptyEntries);
foreach(var batch in lines.Batch(20))
{
foreach(batchLine in batch)
{
Console.Writeline(batchLine);
}
}
static class LinqEx
{
// from http://www.make-awesome.com/2010/08/batch-or-partition-a-collection-with-linq
public static IEnumerable<IEnumerable<T>> Batch<T>(this IEnumerable<T> collection,
int batchSize)
{
List<T> nextbatch = new List<T>(batchSize);
foreach (T item in collection)
{
nextbatch.Add(item);
if (nextbatch.Count == batchSize)
{
yield return nextbatch;
nextbatch = new List<T>(batchSize);
}
}
if (nextbatch.Count > 0)
yield return nextbatch;
}
}

As several people mentioned, using string.Split will split the whole string into memory, which might be an allocation-heavy operation. This is why we have the TextReader class and its descendants, which should provide better memory performance, and might also be clearer, logically:
using (var reader = new StringReader(myString))
{
do
{
StringBuilder newString = null;
StringWriter newStringWriter = null;
if (lineCounter % 20 == 0)
{
newString = new StringBuilder();
newStringWriter = new StringWriter(newString);
newStringCollection.Add(newString);
}
string line = reader.ReadLine();
if (!string.isNullOrEmpty(line))
{
newStringWriter.WriteLine(line);
lineCounter++;
}
}
while (line != null)
}
We're using the StringReader to read our big string, one line at a time. And the corresponding StringWriter writes those lines to the new string, one line a time. After every 20 lines, we start a new StringBuilder (and the appropriate StringWriter wrapper).

split the strings by newline.
Then merge/fetch the number of strings together while using the strings.

string s = "Line1\nThis is line2 \nLine3 is here\nI am Line4";
string [] str = s.split('\n');
List<String> str1 = new List<String>();
for(int i=0; i<str.Length; i+=2)
{
string ss = str[i];
if(i+1 <str.Length)
ss += '\n' + str[i+1];
str1.Add(ss);
}
str = str1.ToArray();
If condition has been checked inside loop because may be the length of str is odd

var strAray = myLongString.Split('\n').ToList();
var skip=0;
var take=20;
var chunk = strAray.Skip(skip).Take(take).ToList();
While(chunk.Count >0)
{
foreach(var line in chunk)
{
// use line string
}
skip++;
chunk = strAray.Skip(skip).Take(take).ToList()
}

Split a string without separator

I have a string variable with value
"abcdefghijklmnop".
Now I want to split the string into string array with, say, three characters (the last array element may contain fewer) in each array element from the right end.
I.e.,
"a"
"bcd"
"efg"
"hij"
"klm"
"nop"
What is the easiest and simplest way to do this?? (Both Visual Basic and C# code is welcome)?

Here's a solution:
var input = "abcdefghijklmnop";
var result = new List<string>();
int incompleteGroupLength = input.Length % 3;
if (incompleteGroupLength > 0)
result.Add(input.Substring(0, incompleteGroupLength));
for (int i = incompleteGroupLength; i < input.Length; i+=3)
{
result.Add(input.Substring(i, 3));
}
It gives the expected output of:
"a"
"bcd"
"efg"
"hij"
"klm"
"nop"

Here's something that works - wrapped up into a string extension function.
namespace System
{
public static class StringExts
{
public static IEnumerable<string> ReverseCut(this string txt, int cutSize)
{
int first = txt.Length % cutSize;
int taken = 0;
string nextResult = new String(txt.Take(first).ToArray());
taken += first;
do
{
if (nextResult.Length > 0)
yield return nextResult;
nextResult = new String(txt.Skip(taken).Take(cutSize).ToArray());
taken += cutSize;
} while (nextResult.Length == cutSize);
}
}
}
Usage:
textBox2.Text = "";
var txt = textBox1.Text;
foreach (string s in txt.ReverseCut(3))
textBox2.Text += s + "\r\n";

Regex time!!
Regex rx = new Regex("^(.{1,2})??(.{3})*$");
var matches = rx.Matches("abcdefgh");
var pieces = matches[0].Groups[1].Captures.OfType<Capture>().Select(p => p.Value).Concat(matches[0].Groups[2].Captures.OfType<Capture>().Select(p => p.Value)).ToArray();
pieces will contain:
"ab"
"cde"
"fgh"
(Please, don't use this code! It is only an example of what can happen when you use a regular expression + LINQ.)

Well... here is yet another way I arrived at:
private string[] splitIntoAry(string str)
{
string[] temp = new string[(int)Math.Ceiling((double)str.Length / 3)];
while (str != string.Empty)
{
temp[(int)Math.Ceiling((double)str.Length / 3) - 1] = str.Substring(str.Length - Math.Min(str.Length, 3));
str = str.Substring(0, str.Length - Math.Min(str.Length, 3));
}
return temp;
}

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