Regx replacing last pattern

April 27, 2022

I have a string which is a file path:

string test = "C:\Users\Folder\File.txt";

what I wanted to do was to replace everything after the last backslash, i.e the filename by test.
I’m trying to do it like so:

            string test = "C:\\Users\\Folder\\File.txt";
            Regex rx = new Regex(@"\\S*(?!.*\\)");
            string result = rx.Replace(test, "\\test.txt");

But this gives me: C:\Users\Folder\test.txtFile.txt" instead of C:\Users\Folder\test.txt", what am I doing wrong?

>Solution :

I wouldn’t do that with Regex but Path really:

string test = "C:\\Users\\Folder\\File.txt";
Regex rx = new Regex(@"\\S*(?!.*\\).*");
string result = rx.Replace(test, "\\test.txt");

Console.WriteLine(result);

var betterWay = Path.Combine(Path.GetDirectoryName(test), "test.txt");
Console.WriteLine(betterWay);