c# Find occurrences of string within a string and wrap text around the matching chars

Split string, example here

 var hello = "Hello World";

I’m trying to get the result to be "Hello World" with spans around the matching "l"

    string[] words = hello.ToLower().Split("l");
    var resultString = "";
    
    for (int i = 0; i < words.Length; i++)
    {
        // now we have split the string how do find the missing 'l' and wrap a span around them
        resultString += words[i].ToString();
    }
    // result is heo word
    Console.WriteLine(resultString);
    // Trying to get the result to be "He<span>l</span><span>l</span>o Wor<span>l<span>d

see dotnetfiddle

>Solution :

var result = Regex.Replace(hello, "l", x => $"<span>{x}</span>");