C# replace a certain word in string except for any urls

Question

I have a large string value and I am trying to find the best way to replace a certain text value out of it without changing any values in a URL.

For instance lets say I want to replace the word "google" with "hello". I have a large string value with multiple instances of "hi" and a url within the string value "https://www.google.com" (this is just an example). Which is the best route to take for replacing these values, potentially a split on the string, regex or a replace?

At the moment I have something like this:

var data = "<h1>google this is a sample text</h1><p> more text will go here so, google. <a href='https://google.com'> Link here </a>";
var test = "";
if(data.Contains("google")){
   test = data.Replace("google", "hello");
}
// for case sensitivity
if(data.Contains("Google")){
   test = data.Replace("Google", "hello");
}

Is there a better alternative to this and would there be a way to not replace the text in a url?

Answer 1

In your very particular case, I would try at first some kind of basic splitting, provided that the tag 'a' is always used and only used to insert the URLs

   private string ReplaceNonUrl_Split(string bigString, string[] substringsToReplace, string[] newStrings)
        {
            string[] Parts = bigString.Split(new string[] { "<a", "</a>" }, StringSplitOptions.None);

            for(int i=0; i<Parts.Length; i++)
            {
                if (Parts[i].Contains("href="))
                {
                    string[] subParts = Parts[i].Split(new string[] { ">" }, StringSplitOptions.None);
                    for (int j = 1; j < subParts.Length; j++)
                    {
                        for (int k = 0; k < newStrings.Length; k++)
                            subParts[j] = subParts[j].Replace(substringsToReplace[k], newStrings[k]);
                    }

                    Parts[i] = string.Join(">", subParts);
                }
                else
                {
                    for (int k = 0; k < newStrings.Length; k++)
                        Parts[i] = Parts[i].Replace(substringsToReplace[k], newStrings[k]);
                }
            }

            string ReplacedString= Parts[0];          
            bool startingURL = true;
            for(int i= 1; i< Parts.Length; i++)
            {
                if (startingURL)
                    ReplacedString += "<a" + Parts[i];
                else
                    ReplacedString += "</a>" + Parts[i];

                startingURL = !startingURL;
            }

            return ReplacedString;
        }

Then call:

   string replacedString = ReplaceNonUrl_Split(data, new string[] { "google", "Google" }, new string[] { "hello", "Hello" });

DISCLAIMER This is just a very manual option. Surely, there already exists libraries that do this for you nicer and efficiently, so I recommend to have a look first to existing html parsers that might fit you.