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C# String append some string ater first occurance of a string after a given string

I know this seems to be very complicated but what i mean is for example i have a string
This is a text string
I want to search for a string (for example: text) . I want to find first occurance of this string which comes after a given another string (for example : is) and the replacement should be another string given (for example: replace)
So the result should be:
This is a textreplace string
If text is This text is a text string then the result should be This text is a textreplace string
I need a method (extension method is appreciated):
public static string AppendFirstOccurranceAfter(this string originalText, string after, string oldValue, string newValue)
// "This is a text string".ReplaceFirstOccurranceAfter("is", "text", "replace")

You have to find the index of the first word to match and then, using that index, do another search for the second word starting at that said index and then you can insert your new text. You can find said indexes with the IndexOf method (check it's overloads).
Here is a simple solution written in a way that (I hope) is readable and that you can likely improve to make more idiomatic:
public static string AppendFirstOccurranceAfter(this string originalText, string after, string oldValue, string newValue) {
var idxFirstWord = originalText.IndexOf(after);
var idxSecondWord = originalText.IndexOf(oldValue, idxFirstWord);
var sb = new StringBuilder();
for (int i = 0; i < originalText.Length; i++) {
if (i == (idxSecondWord + oldValue.Length))
sb.Append(newValue);
sb.Append(originalText[i]);
}
return sb.ToString();
}

Here is the extension method:
public static string CustomReplacement(this string str)
{
string find = "text"; // What you are searching for
char afterFirstOccuranceOf = 'a'; // The character after the first occurence of which you need to find your search term.
string replacement = "$1$2replace"; // What you will replace it with. $1 is everything before the first occurrence of 'a' and $2 is the term you searched for.
string pattern = $"([^{afterFirstOccuranceOf}]*{afterFirstOccuranceOf}.*)({find})";
return Regex.Replace(str, pattern, replacement);
}
You can use it like this:
string test1 = "This is a text string".CustomReplacement();
string test2 = "This text is a text string".CustomReplacement();
This solution uses C# Regular Expressions. The documentation from Microsoft is here: https://learn.microsoft.com/en-us/dotnet/standard/base-types/regular-expression-language-quick-reference

How to get the string data which is outside of parenthesis in C#

I need to get the data which is outside of parenthesis
string data = "English(Language)";
string result= "English";
The result should display the text "English".
I tried with Regex but not able to get the desired result.

Easiest solution that I can think of:
string data = "English(Language)";
string result = data.Substring(0, data.IndexOf('('));
That is of course, if you never need the data within the parenthesis.
Another way to do it is by using String.Split:
string data = "English(Language)";
string result = data.Split('(')[0];
This is marginally slower than the first example since it needs to allocate memory for an array.
The third way to do it is via regular-expressions:
string data = "English(Language)";
var pattern = new Regex("(\\w+\\s?)\\((\\w+)\\)", RegexOptions.Compiled);
string result = pattern.Match(data).Groups[1].Value;
This is the slowest of all the examples, but captures both "English" and "Language". It also allows for whitespace \s? between English and (Language).
A great tool for testing regular expressions is RegexPal, just remember to escape everything when you move it over to C#.
Here is a fiddle, testing the performance of all options.

Try:
string input = "English(Language)";
string regex = "(\\(.*\\))";
string output = Regex.Replace(input, regex, "");
You will need that:
using System.Text.RegularExpressions;

If you dont bother to use Regex, the below solution works fine.
string data = "English(Language)";
string result = Regex.Match(data, #"(.*)\(.*\)").Groups[1].Value;
Console.WriteLine(result); // English

Hi take a look at the Split methods:
string data = "English(Language)";
string result= "English";
var value = data.Split('(').First();
Console.WriteLine (value);
Result :
English

xd or just:
string data = "English(Language)";
string result = data.Replace("(Language)", "");

how to remove last part of string in c#

I was trying to remove last part of a string but failed.Here string named D:\software\VS2012\newtext.txt and i want to trim last section of string so here newtext.txt . I should get D:\software\VS2012 but how to do it in c#.When i tried it is removing all the string that has '\'. Here is what i did in c#
string str = #"D:\softwares\VS2012\newtext.txt";
str= str.Remove(str.IndexOf('\\'));
Console.WriteLine(str);

There is a premade function for this in the framework
string str = #"D:\softwares\VS2012\newtext.txt";
string path = System.IO.Path.GetDirectoryName(str);
(Reference)
Note that your original code does not work because you are removing from the first backslash, not the last. Substitute this line to make your code work
str = str.Remove(str.LastIndexOf('\\'));

Try using System.IO.Path.GetDirectoryName(string):
string dirname= System.IO.Path.GetDirectoryName(#"D:\softwares\VS2012\newtext.txt");

For removing a known portion of a string you can simply use the Replace.
In your case:
str = str.Replace("\\newtext.txt", ""); //this will give you the same result of the System.IO.Path.GetDirectoryName already suggested by gmiley, but it's more in a string context as per your question
Though if you want to remove the last part of a string by the last encounterd known character then the suggested "LastIndexOff('\')" method already suggested along with the Remove.
If you want to use a delimiter method, so depending on the delimiter character but not on the string format (in your case path format) the LastIndexOff(char) is the best option.
Although you could also split the string into an array and then rejoin the array after removing the last element:
var delmimter = '\\';
var strAy = str.Split(char);
str = String.Join('\\', strAy.SkipLast(1).ToArray());
With this method you don't need to rely on the existence of the delimiter char in the string and the result is always without the delimiter char at the end.
Besides, you can easily create an extension with the delimiter as a parameter.

We should check the existance of the char also
string str = #"D:\softwares\VS2012\newtext.txt";
int rstr = str.LastIndexOf('\\');
if (rstr>0) str= str.Remove(rstr);
Console.WriteLine(str);

Replace a substring

I have an input string. I need to replace its prefix (until first dot) with an other string.
The method signature:
string MyPrefixReplace(string input, string replacer)
Examples:
string res = MyPrefixReplace("12.345.6789", "000")
res = "000.345.6789";
res = MyPrefixReplace("908.345.6789", "1")
res = "1.345.6789";
Is there a way not to extract a sub-string before first dot and make a Replace**?
I.e - I don't want this solution
int i = input.IndexOf(".");
string rep = input.Substring(0,i);
input.Replace(rep,replacer);
Thanks

You could use String.Split
public string MyPrefixReplace(string source, string value, char delimiter = '.')
{
var parts = source.Split(delimiter);
parts[0] = value;
return String.Join(delimiter.ToString(), parts);
}
Live demo

Using String.IndexOf and String.Substring ist the most efficient way. In your approach you have used the wrong overload of Substring. String.Replace is pointless anyway since you don't want to replace all occurences of the first part but only the first part.
Therefore you don't have to take but to skip the the first part and prefix another. This works as desired:
public static string MyPrefixReplace(string input, string replacer, char prefixChar = '.')
{
int index = input.IndexOf(prefixChar);
if (index == -1)
return input;
return replacer + input.Substring(index);
}
Your input:
string result = MyPrefixReplace("908.345.6789", "1"); // 1.345.6789
result = MyPrefixReplace("12.345.6789", "000"); // 000.345.6789

Personally, I'd split the string up to get around this problem, although there's obviously other ways of doing this, this would be my approach:
string Input = "123.456.789"
string[] SplitInput = Input.Split('.');
SplitInput[0] = "321";
string Output = String.Join('.', SplitInput);
Output should be "321.456.789".

Pass an array to a function (And use the function to split the array)

I want to pass a string array (separated by commas), then use a function to split the passed array by a comma, and add in a delimiter in place of the comma.
I will show you what I mean in further detail with some broken code:
String FirstData = "1";
String SecondData = "2" ;
String ThirdData = "3" ;
String FourthData = null;
FourthData = AddDelimiter(FirstData,SecondData,ThirdData);
public String AddDelimiter(String[] sData)
{
// foreach ","
String OriginalData = null;
// So, here ... I want to somehow split 'sData' by a ",".
// I know I can use the split function - which I'm having
// some trouble with - but I also believe there is some way
// to use the 'foreach' function? I wish i could put together
// some more code here but I'm a VB6 guy, and the syntax here
// is killing me. Errors everywhere.
return OriginalData;
}

Syntax doesn't matter much here, you need to get to know the Base Class Library. Also, you want to join strings apparently, not split it:
var s = string.Join(",", arrayOFStrings);
Also, if you want to pass n string to a method like that, you need the params keyword:
public string Join( params string[] data) {
return string.Join(",", data);
}

To split:
string[] splitString = sData.Split(new char[] {','});
To join in new delimiter, pass in the array of strings to String.Join:
string colonString = String.Join(":", splitString);
I think you are better off using Replace, since all you want to do is replace one delimiter with another:
string differentDelimiter = sData.Replace(",", ":");

If you have several objects and you want to put them in an array, you can write:
string[] allData = new string[] { FirstData, SecondData, ThirdData };
you can then simply give that to the function:
FourthData = AddDelimiter(allData);
C# has a nice trick, if you add a params keyword to the function definition, you can treat it as if it's a function with any number of parameters:
public String AddDelimiter(params String[] sData) { … }
…
FourthData = AddDelimiter(FirstData, SecondData, ThirdData);
As for the actual implementation, the easiest way is to use string.Join():
public String AddDelimiter(String[] sData)
{
// you can use any other string instead of ":"
return string.Join(":", sData);
}
But if you wanted to build the result yourself (for example if you wanted to learn how to do it), you could do it using string concatenation (oneString + anotherString), or even better, using StringBuilder:
public String AddDelimiter(String[] sData)
{
StringBuilder result = new StringBuilder();
bool first = true;
foreach (string s in sData)
{
if (!first)
result.Append(':');
result.Append(s);
first = false;
}
return result.ToString();
}

One version of the Split function takes an array of characters. Here is an example:
string splitstuff = string.Split(sData[0],new char [] {','});

If you don't need to perform any processing on the parts in between and just need to replace the delimiter, you could easily do so with the Replace method on the String class:
string newlyDelimited = oldString.Replace(',', ':');
For large strings, this will give you better performance, as you won't have to do a full pass through the string to break it apart and then do a pass through the parts to join them back together.
However, if you need to work with the individual parts (to recompose them into another form that does not resemble a simple replacement of the delimiter), then you would use the Split method on the String class to get an array of the delimited items and then plug those into the format you wish.
Of course, this means you have to have some sort of explicit knowledge about what each part of the delimited string means.