Why does my Regex.Replace string contain the replacement value twice?

Question

I have the following string: aWesdE, which I want to convert to http://myserver.com/aWesdE.jpg using Regex.Replace(string, string, string, RegexOptions)

Currently, I use this code:

string input = "aWesdE";
string match = "(.*)";
string replacement = "http://myserver.com/$1.jpg";
string output = Regex.Replace(input, match, replacement,
          RegexOptions.IgnoreCase | RegexOptions.Singleline);

The result is that output is ending up as: http://myserver.com/aWesdE.jpghttp://myserver.com/.jpg

So, the replacement value shows up correctly, and then appears to be appended again - very strange. What's going on here?

Answer 1

There are actually 2 matches in your Regex. You defined your match like this:

string match = "(.*)";

It means match zero or more characters, so you have 2 matches - empty string and your text. In order to fix it change the pattern to

string match = "(.+)";

It means match one or more characters - in that case you will only get a single match