I have a string that may or may not have multiple matches for a designated pattern.
Each needs to be replaced.
I have this code:
var pattern = @"\$\$\@[a-zA-Z0-9_]*\b";
var stringVariableMatches = Regex.Matches(strValue, pattern);
var sb = new StringBuilder(strValue);
foreach (Match stringVarMatch in stringVariableMatches)
{
var stringReplacment = variablesDictionary[stringVarMatch.Value];
sb.Remove(stringVarMatch.Index, stringVarMatch.Length)
.Insert(stringVarMatch.Index, stringReplacment);
}
return sb.ToString();
The problem is that when I have several matches the first is replaced and the starting index of the other is changed so that in some cases after the replacement when the string is shorten I get an index out of bounds..
I know I could just use Regex.Replace for each match but this sound performance heavy and wanted to see if someone could point a different solution to substitute multiple matches each with a different string.
Use a Match evaluator inside the Regex.Replace:
var pattern = @"\$\$\@[a-zA-Z0-9_]*\b";
var stringVariableMatches = Regex.Replace(strValue, pattern,
m => variablesDictionary[m.Value]);
The Regex.Replace method will perform global replacements, i.e. will search for all non-overlapping substrings that match the indicated pattern, and will replace each found match value with the variablesDictionary[m.Value].
Note that it might be a good idea to check if the key exists in the dictionary.
See a C# demo:
using System;
using System.IO;
using System.Text.RegularExpressions;
using System.Collections.Generic;
using System.Linq;
public class Test
{
public static void Main()
{
var variablesDictionary = new Dictionary<string, string>();
variablesDictionary.Add("$$@Key", "Value");
var pattern = @"\$\$@[a-zA-Z0-9_]+\b";
var stringVariableMatches = Regex.Replace("$$@Unknown and $$@Key", pattern,
m => variablesDictionary.ContainsKey(m.Value) ? variablesDictionary[m.Value] : m.Value);
Console.WriteLine(stringVariableMatches);
}
}
Output: $$@Unknown and Value.
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