Replace string in C#

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example:

String str = "1 2 3 4 5 6 7 8 9";
Console.WriteLine("Original string: \"{0}\"", str);
Console.WriteLine("CSV string:      \"{0}\"", str.Replace(' ', ','));

if I want to substitute not all empty spaces but only the second and the third, how must I write?

What I have tried:

I tried to use the code that I wrote above

Posted 11-Apr-23 21:53pm

Member 14594285

Updated 13-Apr-23 2:22am

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Comments

PIEBALDconsult 12-Apr-23 11:49am

Use a Regular Expression.

5 solutions

Solution 4

If you are familiar with Linq you can try something along these lines

.

C#

string str = "1 2 3 4 5 6 7 8 9";
  int[] spacesToReplace = new int[] { 2, 3 };//replace only the 2nd and third space
  //select the index value of each space in the string
  var spaceIndices = str.Select((c, i) => c == ' ' ? i : -1).Where((i) => i != -1).ToArray();
  //select the spaces that need to be replaced
  var targetedSpaces = spacesToReplace.Select((n) => spaceIndices[n - 1]);
  //replace the selected spaces with a ','
  var charArray = str.Select((c, i) => targetedSpaces.Contains(i) ? ',' : c).ToArray();
  //build a new string the easy way
  string updatedString = new(charArray);

  Console.WriteLine($"Updated string: {updatedString}");
  //prints Updated string: 1 2,3,4 5 6 7 8 9

Posted 12-Apr-23 3:15am

George Swan

Solution 2

Try a regex:

RegEx

(?<=^\d+\s\d+)(\s)(?<digit>\d+)(\s)(?=.*)

With a replacement string of

RegEx

${digit}

Posted 11-Apr-23 22:21pm

OriginalGriff

Solution 3

Assuming I have understood the required result, I tried a C# approach.

String str = "1 2 3 4 5 6 7 8 9";

Console.WriteLine("Original string: \"{0}\"", str);
Console.WriteLine("CSV string:      \"{0}\"", str.Replace(' ', ','));

var chars = new List<char>();
chars.AddRange(str);
chars.RemoveAt(3);
chars.RemoveAt(4);
var result = String.Join("", chars);

Console.WriteLine("New CSV string:      \"{0}\"", result.Replace(' ', ','));
Console.ReadKey();

This converts the string to a list, removes the spaces at position 3 & 5, and converts the list back to a string.

The output:

New CSV string:      "1,234,5,6,7,8,9"

Posted 12-Apr-23 0:21am

Kuv Patel

Updated 12-Apr-23 0:23am

v2

Solution 5

You can separate the contents by using split (this will remove the double spaces)

string[] values=str.Split();
or
string[] values=str.Split(' ');

the second sptep is join it again with

string newSTR=string.Join(",", values);

Posted 13-Apr-23 2:22am

Member 10871197

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Richard MacCutchan · Accepted Answer · 2023-04-11T22:02:00

Solution 1

The Replace method is used to replace all occurrences. To restrict it to specific positions you probably need something like the String.Chars[Int32] Property (System) | Microsoft Learn[^].

Posted 11-Apr-23 22:02pm

Richard MacCutchan

Comments

Member 14594285 12-Apr-23 5:12am

yes but this is for a char..but if I must substitute a substring how must I write?

Richard MacCutchan 12-Apr-23 5:29am

You can still replace more than one character using a simple loop. Alternatively you could use the Substring method to separate the two parts. You can then do the replacement for the part you need, and recombine them to get the final string.