String.Replace method ignores case with special characters.

Question

I have a string containing a server file path ($\\MyPath\\Quotas\\ExactPath\\MyFile.txt) and a local file system path (C:\\MyLocalPath\\Quotas\\ExactPath). I want to replace the server file path with the local system path.

I currently have an exact replace:

String fPath = @"$\MyPath\Quotas\ExactPath\MyFile.txt";
String sPath = @"$\MyPath\Quotas\ExactPath\";
String lPath = @"C:\MyLocalPath\Quotas\ExactPath\";

String newPath = fPath.Replace(sPath, lPath);

But I want this to be a case-insensitive replace, so that it would replace $\\MyPath\\quotas\\Exactpath\\ with lPath as well.

I came across the use of Regular Expressions like the following:

var regex = new Regex( sPath, RegexOptions.IgnoreCase );
var newFPath = regex.Replace( fPath, lPath );

But how do I handle the special characters ($,\\,/,:) so that it is not interpreted as a regular expression special character?

Answer 1

You can use Regex.Escape :

var regex = new Regex(Regex.Escape(sPath), RegexOptions.IgnoreCase);
var newFPath = regex.Replace(fPath, lPath);

Answer 2

Just use Regex.Escape :

fPath = Regex.Escape(fPath);

This escapes all metacharacters and turns them into literals.

Answer 3

As you are only after the case sensetivity setting, and not any regular expression matching, you should rather use String.Replace rather than Regex.Replace . Surprisingly enough there is no overload of the Replace method that takes any culture or comparison settings, but that can be fixed with an extension method:

public static class StringExtensions {

  public static string Replace(this string str, string match, string replacement, StringComparison comparison) {
    int index = 0, newIndex;
    StringBuilder result = new StringBuilder();
    while ((newIndex = str.IndexOf(match, index, comparison)) != -1) {
      result.Append(str.Substring(index, newIndex - index)).Append(replacement);
      index = newIndex + match.Length;
    }
    return index > 0 ? result.Append(str.Substring(index)).ToString() : str;
  }

}

Usage:

String newPath = fPath.Replace(sPath, lPath, StringComparison.OrdinalIgnoreCase);

Testing the performance, this shows to be 10-15 times faster than using Regex.Replace .

Answer 4

I would recommend not using Replace at all. Use the Path class in System.IO:

string fPath = @"$\MyPath\Quotas\ExactPath\MyFile.txt";
string lPath = @"C:\MyLocalPath\Quotas\ExactPath\";

string newPath = Path.Combine(lPath, Path.GetFileName(fPath));