Using Regex.Replace to keep characters that can be vary

Question

I have the following:

string text = \"version=\\\"1,0\\\"\";

I want to replace the comma for a dot, while keeping

Answer 1

You can perhaps use capture groups to keep the numbers in front and after for replacement afterwards for a more 'traditional way' to do it:

string text = "version=\"1,0\"";
var regex = new Regex(@"version=""(\d*),(\d*)""");
var result = regex.Replace(text, "version=\"$1.$2\"");

Using parens like the above in a regex is to create a capture group (so the matched part can be accessed later when needed) so that in the above, the digits before and after the comma will be stored in $1 and $2 respectively.

---

But I decided to delve a little bit further and let's consider the case if there are more than one comma to replace in the version, i.e. if the text was version="1,1,0". It would actually be tedious to do the above, and you would have to make one replace for each 'type' of version. So here's one solution that is sometimes called a callback in other languages (not a C# dev, but I fiddled around lambda functions and it seems to work :)):

private static string SpecialReplace(string text)
{
    var result = text.Replace(',', '.');
    return result;
}
public static void Main()
{
    string text = "version=\"1,0,0\"";
    var regex = new Regex(@"version=""[\d,]*""");
    var result = regex.Replace(text, x => SpecialReplace(x.Value));
    Console.WriteLine(result);
}

The above gives version="1.0.0".

"version=""[\d,]*""" will first match any sequence of digits and commas within version="...", then pass it to the next line for the replace.

The replace takes the matched text, passes it to the lambda function which takes it to the function SpecialReplace, where a simple text replace is carried out only on the matched part.

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