I currently have the code below, to replace a characters in a string but I now need to replace characters within the first X (in this case 3) characters and leave the rest of the string. In my example below I have 51115 but I need to replace any 5 within the first 3 characters and I should end up with 61115.
My current code:
value = 51115;
oldString = 5;
newString = 6;
result = Regex.Replace(value.ToString(), oldString, newString, RegexOptions.IgnoreCase);
result is now 61116. What would you suggest I do to query just the first x characters?
Thanks
Not particularly fancy, but only give regex the data it should be replacing; only send in the range of characters that should potentially be replaced.
result = Regex.Replace(value.ToString().Substring(0, x), oldString, newString, RegexOptions.IgnoreCase);
If you're just replacing a single character only, you could just write the code to do the replacement yourself. It'd be faster than messing with a substring and then a RegEx replace (which is a waste anyway if you're doing a single-char replacement).
StringBuilder sb = new StringBuilder(oldString.Length);
foreach(char c in oldString) {
if(c == replaceFrom) { c = replaceTo; }
sb.Append(c);
}
return sb.ToString();
I think the character-by-character option mentioned here is probably clearer, but if you really want a regex:
string result = "";
int value = 55555;
string oldString = "5";
string newString = "6";
var match = new Regex(#"(\d{1,3})(\d+)?").Match(value.ToString());
if (match.Groups.Count > 1)
result = match.Groups[1].Value.Replace(oldString, newString) + (match.Groups.Count > 2 ? match.Groups[2].Value : "");
I love RegEx, but in this case I would just do a .Replace
string value;
string oldString;
string newString;
value = "51115";
int iLenToLook;
iLenToLook = 3;
oldString = "5";
newString = "6";
string result;
result = value.Length > iLenToLook ? value.Substring(iLenToLook, value.Length - iLenToLook) :"";
result = value.Substring(0, value.Length >= iLenToLook ? iLenToLook : value.Length).Replace(oldString, newString) + result;
EDIT I changed it to get the non-replaced portion first, in case there were replacement strings of differing lengths than the original.
Every time someone in the .NET world has a question about regex, I recommend Expresso (link). It's a great tool for working in the confusing and thorny world of regular expressions.
Related
I have a input string like -
abbdabab
How to replace only the 2nd, 3rd and subsequent occurances of the substring "ab" with any random string like "x" keeping the original string intact. Example in this case -
1st Output - xbdabab 2nd Output - abbdxab 3rd Output - abbdabx and so on...
I have tried using Regex like -
int occCount = Regex.Matches("abbdabab", "ab").Count;
if (occCount > 1)
{
for (int i = 1; i <= occCount; i++)
{
Regex regReplace = new Regex("ab");
string modifiedValue = regReplace.Replace("abbdabab", "x", i);
//decodedMessages.Add(modifiedValue);
}
}
Here I am able to get the 1st output when the counter i value is 1 but not able to get the subsequent results. Is there any overloaded Replace method which could achieve this ? Or Can anyone help me in pointing where I might have gone wrong?
You can try IndexOf instead of regular expressions:
string source = "abbdabab";
string toFind = "ab";
string toSet = "X";
for (int index = source.IndexOf(toFind);
index >= 0;
index = source.IndexOf(toFind, index + 1)) {
string result = source.Substring(0, index) +
toSet +
source.Substring(index + toFind.Length);
Console.WriteLine(result);
}
Outcome:
Xbdabab
abbdXab
abbdabX
You can use a StringBuilder:
string s = "abbdabab";
var matches = Regex.Matches(s, "ab");
StringBuilder sb = new StringBuilder(s);
var m = matches[0]; // 0 for first output, 1 for second output, and so on
sb.Remove(m.Index, m.Length);
sb.Insert(m.Index, "x");
var result = sb.ToString();
Console.WriteLine(result);
You may use a dynamically built regex to be used with regex.Replace directly:
var s = "abbdabab";
var idx = 1; // First = 1, Second = 2
var search = "ab";
var repl = "x";
var pat = new Regex($#"(?s)((?:{search}.*?){{{idx-1}}}.*?){search}"); // ((?:ab.*?){0}.*?)ab
Console.WriteLine(pat.Replace(s, $"${{1}}{repl}", 1));
See the C# demo
The pattern will look like ((?:ab.*?){0}.*?)ab and will match
(?s) - RegexOptions.Singleline to make . also match newlines
((?:ab.*?){0}.*?) - Group 1 (later, this value will be put back into the result with ${1} backreference)
(?:ab.*?){0} - 0 occurrences of ab followed with any 0+ chars as few as possible
.*? - any 0+ chars as few as possible
ab - the search string/pattern.
The last argument to pat.Replace is 1, so that only the first occurrence could be replaced.
If search is a literal text, you need to use var search = Regex.Escape("a+b");.
If the repl can have $, add repl = repl.Replace("$", "$$");.
For example, TOMILA RELEASE V6.24 , i want to get 6.24 i used
if (txt.Contains("<TOMILA RELEASE"))
{
int iStartIndex = txt.LastIndexOf("<TOMILA RELEASE") + 17;
for (int i = 0; i < 50; i++) {
if (txt[iStartIndex + i] == '>') break;
currentRelease += txt[iStartIndex + i];
}
}
So, my question is if i want to get the specific 6 from TOMILA RELEASE V6.24, how could i get it?
You can try LastIndexOf followed by Substring
var result = str.Substring(str.LastIndexOf('TOMILA RELEASE V') + 1);
If you want to take first number in the string you can use following regular expression.
string s = "TOMILA RELEASE V6.24";
string digit = Regex.Match(s, "\\d").Value;
Here \d is for matching the digit, you can find more about regular expression in this tutorial, The 30 Minute Regex Tutorial
If you want to extract all number before dot then you can add + with \d and use do to end the extraction.
string number = Regex.Match(s, "\\d+.").Value.Replace(".","");
If you want to get a specific portion of a string, you could use the below code
string str = "6.24";
var val = str.Substring(0, 1);
For example I have such string:
ex250-r-ninja-08-10r_
how could I change it to such string?
ex250 r ninja 08-10r_
as you can see I change all - to space, but didn't change it where I have XX-XX part... how could I do such string replacement in c# ? (also string could be different length)
I do so for -
string correctString = errString.Replace("-", " ");
but how to left - where number pattern XX-XX ?
You can use regular expressions to only perform substitutions in certain cases. In this case, you want to perform a substitution if either side of the dash is a non-digit. That's not quite as simple as it might be, but you can use:
string ReplaceSomeHyphens(string input)
{
string result = Regex.Replace(input, #"(\D)-", "${1} ");
result = Regex.Replace(result, #"-(\D)", " ${1}");
return result;
}
It's possible that there's a more cunning way to do this in a single regular expression, but I suspect that it would be more complicated too :)
A very uncool approach using a StringBuilder. It'll replace all - with space if the two characters before and the two characters behind are not digits.
StringBuilder sb = new StringBuilder();
for (int i = 0; i < text.Length; i++)
{
bool replace = false;
char c = text[i];
if (c == '-')
{
if (i < 2 || i >= text.Length - 2) replace = true;
else
{
bool leftDigit = text.Substring(i - 2, 2).All(Char.IsDigit);
bool rightDigit = text.Substring(i + 1, 2).All(Char.IsDigit);
replace = !leftDigit || !rightDigit;
}
}
if (replace)
sb.Append(' ');
else
sb.Append(c);
}
Since you say you won't have hyphens at the start of your string then you need to capture every occurrence of - that is preceded by a group of characters which contains at least one letter and zero or many numbers. To achieve this, use positive lookbehind in your regex.
string strRegex = #"(?<=[a-z]+[0-9]*)-";
Regex myRegex = new Regex(strRegex, RegexOptions.IgnoreCase | RegexOptions.Multiline);
string strTargetString = #"ex250-r-ninja-08-10r_";
string strReplace = #" ";
return myRegex.Replace(strTargetString, strReplace);
Here are the results:
I want to trim a string after a special character..
Lets say the string is str="arjunmenon.uking". I want to get the characters after the . and ignore the rest. I.e the resultant string must be restr="uking".
How about:
string foo = str.EverythingAfter('.');
using:
public static string EverythingAfter(this string value, char c)
{
if(string.IsNullOrEmpty(value)) return value;
int idx = value.IndexOf(c);
return idx < 0 ? "" : value.Substring(idx + 1);
}
you can use like
string input = "arjunmenon.uking";
int index = input.LastIndexOf(".");
input = input.Substring(index+1, input.Split('.')[1].ToString().Length );
Use Split function
Try this
string[] restr = str.Split('.');
//restr[0] contains arjunmenon
//restr[1] contains uking
char special = '.';
var restr = str.Substring(str.IndexOf(special) + 1).Trim();
Try Regular Expression Language
using System.IO;
using System;
using System.Text.RegularExpressions;
class Program
{
static void Main()
{
string input = "arjunmenon.uking";
string pattern = #"[a-zA-Z0-9].*\.([a-zA-Z0-9].*)";
foreach (Match match in Regex.Matches(input, pattern))
{
Console.WriteLine(match.Value);
if (match.Groups.Count > 1)
for (int ctr = 1; ctr < match.Groups.Count; ctr++)
Console.WriteLine(" Group {0}: {1}", ctr, match.Groups[ctr].Value);
}
}
}
Result:
arjunmenon.uking
Group 1: uking
Personally, I won't do the split and go for the index[1] in the resulting array, if you already know that your correct stuff is in index[1] in the splitted string, then why don't you just declare a constant with the value you wanted to "extract"?
After you make a Split, just get the last item in the array.
string separator = ".";
string text = "my.string.is.evil";
string[] parts = text.Split(separator);
string restr = parts[parts.length - 1];
The variable restr will be = "evil"
string str = "arjunmenon.uking";
string[] splitStr = str.Split('.');
string restr = splitStr[1];
Not like the methods that uses indexes, this one will allow you not to use the empty string verifications, and the presence of your special caracter, and will not raise exceptions when having empty strings or string that doesn't contain the special caracter:
string str = "arjunmenon.uking";
string restr = str.Split('.').Last();
You may find all the info you need here : http://msdn.microsoft.com/fr-fr/library/b873y76a(v=vs.110).aspx
cheers
I think the simplest way will be this:
string restr, str = "arjunmenon.uking";
restr = str.Substring(str.LastIndexOf('.') + 1);
Is there any way to take a part out of a regex? Let's say I have a match for this
\s*(string)\s*(.*\()\s*(\d*)\)\s*;?(.*)
and I want to change it like this
Regex.Replace(line, #"\s*(string)\s*(.*\()\s*(\d*)\)\s*;?(.*)", "$1 $2($3) // $4", RegexOptions.IgnoreCase);
Is there any way I can grab the $4 by itself and set it equal to some string variable?
Let's say the regex match is: string (55) ;comment
In this case I'd like to get the word comment only and set it to a string without going through the String.Split function. Ultimately, though, I'd just like to get the digits between the parentheses.
There's an overload for the Replace method which takes a MatchEvaluator delegate:
string pattern = "...";
string result = Regex.Replace(line, pattern, m =>
{
int digits = 0;
string comment = m.Groups[4].Value; // $4
int.TryParse(m.Groups[3].Value, out digits); // $3
return string.Format("{0} {1}({2}) // {3}",
m.Groups[1].Value, m.Groups[2].Value, digits, comment);
}, RegexOptions.IgnoreCase);
Hope this helps.
Yes, if I understand the question correctly:
var re = new Regex(#"\s*(string)\s*(.*\()\s*(\d*)\)\s*;?(.*)");
var match = re.Match(input);
if (match.Success)
{
int i = match.Groups[4].Index;
int n = match.Groups[4].Length;
input = input.Substring(0, i) + replacementString + input.Substring(i + n);
}