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From end to start how to get everything from the 5th occurence of "-"?

I have this string:
abc-8479fe75-82rb5-45g00-b563-a7346703098b
I want to go through this string starting from the end and grab everything till the 5th occurence of the "-" sign.
how do I substring this string to only show (has to be through the procedure described above): -8479fe75-82rb5-45g00-b563-a7346703098b

You can also define handy extension method if that's common use case:
public static class StringExtensions
{
public static string GetSubstringFromReversedOccurence(this string #this,
char #char,
int occurence)
{
var indexes = new List<int>();
var idx = 0;
while ((idx = #this.IndexOf(#char, idx + 1)) > 0)
{
indexes.Add(idx);
}
if (occurence > indexes.Count)
{
throw new Exception("Not enough occurences of character");
}
var desiredIndex = indexes[indexes.Count - occurence];
return #this.Substring(desiredIndex);
}
}

According to your string rules, I would do a simple split :
var text = "abc-8479fe75-82rb5-45g00-b563-a7346703098b";
var split = text.split('-');
if (split.Lenght <= 5)
return text;
return string.Join('-', split.Skip(split.Lenght - 5);

We could use a regex replacement with a capture group:
var text = "abc-8479fe75-82rb5-45g00-b563-a7346703098b";
var pattern = #"([^-]+(?:-[^-]+){4}).*";
var output = Regex.Replace(text, pattern, "$1");
Console.WriteLine(output); // abc-8479fe75-82rb5-45g00-b563
If we can rely on the input always having 6 hyphen separated components, we could also use this version:
var text = "abc-8479fe75-82rb5-45g00-b563-a7346703098b";
var pattern = #"-[^-]+$";
var output = Regex.Replace(text, pattern, "");
Console.WriteLine(output); // abc-8479fe75-82rb5-45g00-b563

I think this should be the most performant
public string GetSubString(string text)
{
var count = 0;
for (int i = text.Length-1; i > 0; i--)
{
if (text[i] == '-') count++;
if (count == 5) return text.Substring(i);
}
return null;
}

Using indexOf (C#) to remove a set of characters from a string

public static string shita1(string st1)
{
string st2 = "", stemp = st1;
int i;
for(i=0; i<stemp.Length; i++)
{
if (stemp.IndexOf("cbc") == i)
{
i += 2 ;
stemp = "";
stemp = st1.Substring(i);
i = 0;
}
else
st2 = st2 + stemp[i];
}
return st2;
}
static void Main(string[] args)
{
string st1;
Console.WriteLine("enter one string:");
st1 = Console.ReadLine();
Console.WriteLine(shita1(st1));
}
}
i got a challange from my college, the challange is to move any "cbc" characters from a string...
this is my code... it works when i use only one "cbc" but when i use 2 of them it stucks... help please :)

The IndexOf Method gives you everything you need to know.
Per the documentation.
Reports the zero-based index of the first occurrence of a specified
Unicode character or string within this instance. The method returns
-1 if the character or string is not found in this instance.
This means you can create a loop that repeats as long as the returned index is not -1 and you don't have to loop through the string testing letter by letter.

I think this should work just tested it on some examples. Doesn't use string.Replace or IndexOf
static void Main(string[] args)
{
Console.WriteLine("enter one string:");
var input = Console.ReadLine();
Console.WriteLine(RemoveCBC(input));
}
static string RemoveCBC(string source)
{
var result = new StringBuilder();
for (int i = 0; i < source.Length; i++)
{
if (i + 2 == source.Length)
break;
var c = source[i];
var b = source[i + 1];
var c2 = source[i + 2];
if (c == 'c' && c2 == 'c' && b == 'b')
i = i + 2;
else
result.Append(source[i]);
}
return result.ToString();
}

You can use Replace to remove/replace all occurances of a string inside another string:
string original = "cbc_STRING_cbc";
original = original.Replace("cbc", String.Empty);

If you want remove characters from string using only IndexOf method you can use this code.
public static string shita1(string st1)
{
int index = -1;
string yourMatchingString = "cbc";
while ((index = st1.IndexOf(yourMatchingString)) != -1)
st1 = st1.Remove(index, yourMatchingString.Length);
return st1;
}
This code remove all inputs of you string.
But you can do it just in one line:
st1 = st1.Replace("cbc", string.Empty);
Hope this help.

Changing a specific part of a string

In C#, I got a string which looks in the following format:
a number|a number|a number,a number
for example: 1|2|3,4
I consider each number as the different part of the string. in the previous example, 1 is the first part, 2 is the second and so on.
I want to be able to replace a specific part of the string given an index of the part I want to change.
It's not that hard to do it with String.Split but that part with the comma makes it tedious since then i need to check if the index is 3 or 4 and then also separate with the comma.
Is there a more elegant way to do a switch of a specific part in the string? maybe somehow with a regular expression?
EDIT: I will add some requirements which I didn't write before:
What if I want to for example take the 3rd part of the string and replace it with the number there and add it 2. for example 1|2|3,4 to 1|2|5,4 where the 5 is NOT a constant but depends on the input string given.

You can create the following method
static string Replace(string input, int index, string replacement)
{
int matchIndex = 0;
return Regex.Replace(input, #"\d+", m => matchIndex++ == index ? replacement : m.Value);
}
Usage:
string input = "1|2|3,4";
string output = Replace(input, 1, "hello"); // "1|hello|3,4
As Eric Herlitz suggested, you can use other regex, the negative of delimiters. For example, if you expect , and | delimiters, you can replace \d+ by [^,|]+ regex. If you expect ,, | and # delimiters, you can use [^,|#] regex.
If you need to do some mathematical operations, you're free to do so:
static string Replace(string input, int index, int add)
{
int matchIndex = 0;
return Regex.Replace(input, #"\d+", m => matchIndex++ == index ? (int.Parse(m.Value) + add).ToString() : m.Value );
}
Example:
string input = "1|2|3,4";
string output = Replace(input, 2, 2); // 1|2|5,4
You can even make it generic:
static string Replace(string input, int index, Func<string,string> operation)
{
int matchIndex = 0;
return Regex.Replace(input, #"\d+", m => matchIndex++ == index ? operation(m.Value) : m.Value);
}
Example:
string input = "1|2|3,4";
string output = Replace(input, 2, value => (int.Parse(value) + 2).ToString()); // 1|2|5,4

Try this:
static void Main()
{
string input = "1|2|3|4,5,6|7,8|9|23|29,33";
Console.WriteLine(ReplaceByIndex(input, "hello", 23));
Console.ReadLine();
}
static string ReplaceByIndex(string input, string replaceWith, int index)
{
int indexStart = input.IndexOf(index.ToString());
int indexEnd = input.IndexOf(",", indexStart);
if (input.IndexOf("|", indexStart) < indexEnd)
indexEnd = input.IndexOf("|", indexStart);
string part1 = input.Substring(0, indexStart);
string part2 = "";
if (indexEnd > 0)
{
part2 = input.Substring(indexEnd, input.Length - indexEnd);
}
return part1 + replaceWith + part2;
}
This is assuming the numbers are in ascending order.

Use Regex.Split for the input and Regex.Match to collect your delimiters
string input = "1|2|3,4,5,6|7,8|9";
string pattern = #"[,|]+";
// Collect the values
string[] substrings = Regex.Split(input, pattern);
// Collect the delimiters
MatchCollection matches = Regex.Matches(input, pattern);
// Replace anything you like, i.e.
substrings[3] = "222";
// Rebuild the string
int i = 0;
string newString = string.Empty;
foreach (string substring in substrings)
{
newString += string.Concat(substring, matches.Count >= i + 1 ? matches[i++].Value : string.Empty);
}
This will output "1|2|3,222,5,6|7,8|9"

Try this (tested):
public static string Replace(string input, int value, int index)
{
string pattern = #"(\d+)|(\d+)|(\d+),(\d+)";
return Regex.Replace(input, pattern, match =>
{
if (match.Index == index * 2) //multiply by 2 for | and , character.
{
return value.ToString();
}
return match.Value;
});
}
Usage example:
string input = "1|2|3,4";
string output = Replace(input, 9, 1);
Updated with new requirement:
public static string ReplaceIncrement(string input, int incrementValue, int index)
{
string pattern = #"(\d+)|(\d+)|(\d+),(\d+)";
return Regex.Replace(input, pattern, match =>
{
if (match.Index == index * 2)
{
return (int.Parse(match.Value) + incrementValue).ToString();
}
return match.Value;
});
}

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;
}

Find a string between 2 known values

I need to be able to extract a string between 2 tags for example: "00002" from "morenonxmldata<tag1>0002</tag1>morenonxmldata"
I am using C# and .NET 3.5.

Regex regex = new Regex("<tag1>(.*)</tag1>");
var v = regex.Match("morenonxmldata<tag1>0002</tag1>morenonxmldata");
string s = v.Groups[1].ToString();
Or (as mentioned in the comments) to match the minimal subset:
Regex regex = new Regex("<tag1>(.*?)</tag1>");
Regex class is in System.Text.RegularExpressions namespace.

Solution without need of regular expression:
string ExtractString(string s, string tag) {
// You should check for errors in real-world code, omitted for brevity
var startTag = "<" + tag + ">";
int startIndex = s.IndexOf(startTag) + startTag.Length;
int endIndex = s.IndexOf("</" + tag + ">", startIndex);
return s.Substring(startIndex, endIndex - startIndex);
}

A Regex approach using lazy match and back-reference:
foreach (Match match in Regex.Matches(
"morenonxmldata<tag1>0002</tag1>morenonxmldata<tag2>abc</tag2>asd",
#"<([^>]+)>(.*?)</\1>"))
{
Console.WriteLine("{0}={1}",
match.Groups[1].Value,
match.Groups[2].Value);
}

Extracting contents between two known values can be useful for later as well. So why not create an extension method for it. Here is what i do, Short and simple...
public static string GetBetween(this string content, string startString, string endString)
{
int Start=0, End=0;
if (content.Contains(startString) && content.Contains(endString))
{
Start = content.IndexOf(startString, 0) + startString.Length;
End = content.IndexOf(endString, Start);
return content.Substring(Start, End - Start);
}
else
return string.Empty;
}

string input = "Exemple of value between two string FirstString text I want to keep SecondString end of my string";
var match = Regex.Match(input, #"FirstString (.+?) SecondString ").Groups[1].Value;

To get Single/Multiple values without regular expression
// For Single
var value = inputString.Split("<tag1>", "</tag1>")[1];
// For Multiple
var values = inputString.Split("<tag1>", "</tag1>").Where((_, index) => index % 2 != 0);

For future reference, I found this code snippet at http://www.mycsharpcorner.com/Post.aspx?postID=15 If you need to search for different "tags" it works very well.
public static string[] GetStringInBetween(string strBegin,
string strEnd, string strSource,
bool includeBegin, bool includeEnd)
{
string[] result ={ "", "" };
int iIndexOfBegin = strSource.IndexOf(strBegin);
if (iIndexOfBegin != -1)
{
// include the Begin string if desired
if (includeBegin)
iIndexOfBegin -= strBegin.Length;
strSource = strSource.Substring(iIndexOfBegin
+ strBegin.Length);
int iEnd = strSource.IndexOf(strEnd);
if (iEnd != -1)
{
// include the End string if desired
if (includeEnd)
iEnd += strEnd.Length;
result[0] = strSource.Substring(0, iEnd);
// advance beyond this segment
if (iEnd + strEnd.Length < strSource.Length)
result[1] = strSource.Substring(iEnd
+ strEnd.Length);
}
}
else
// stay where we are
result[1] = strSource;
return result;
}

I strip before and after data.
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Text.RegularExpressions;
namespace testApp
{
class Program
{
static void Main(string[] args)
{
string tempString = "morenonxmldata<tag1>0002</tag1>morenonxmldata";
tempString = Regex.Replace(tempString, "[\\s\\S]*<tag1>", "");//removes all leading data
tempString = Regex.Replace(tempString, "</tag1>[\\s\\S]*", "");//removes all trailing data
Console.WriteLine(tempString);
Console.ReadLine();
}
}
}

Without RegEx, with some must-have value checking
public static string ExtractString(string soapMessage, string tag)
{
if (string.IsNullOrEmpty(soapMessage))
return soapMessage;
var startTag = "<" + tag + ">";
int startIndex = soapMessage.IndexOf(startTag);
startIndex = startIndex == -1 ? 0 : startIndex + startTag.Length;
int endIndex = soapMessage.IndexOf("</" + tag + ">", startIndex);
endIndex = endIndex > soapMessage.Length || endIndex == -1 ? soapMessage.Length : endIndex;
return soapMessage.Substring(startIndex, endIndex - startIndex);
}

public string between2finer(string line, string delimiterFirst, string delimiterLast)
{
string[] splitterFirst = new string[] { delimiterFirst };
string[] splitterLast = new string[] { delimiterLast };
string[] splitRes;
string buildBuffer;
splitRes = line.Split(splitterFirst, 100000, System.StringSplitOptions.RemoveEmptyEntries);
buildBuffer = splitRes[1];
splitRes = buildBuffer.Split(splitterLast, 100000, System.StringSplitOptions.RemoveEmptyEntries);
return splitRes[0];
}
private void button1_Click(object sender, EventArgs e)
{
string manyLines = "Received: from exim by isp2.ihc.ru with local (Exim 4.77) \nX-Failed-Recipients: rmnokixm#gmail.com\nFrom: Mail Delivery System <Mailer-Daemon#isp2.ihc.ru>";
MessageBox.Show(between2finer(manyLines, "X-Failed-Recipients: ", "\n"));
}