Most efficient way to replace HTML special entities to custom string

Question

I want to replace ALL HTML special entities like > < to custom string.

Lets say i have following string:

string str = "<div>&gt;hello&lt;</div>";

and method: Method(string str, string replaceStr)

After calling Method(str, ":)") result should be

<div>:)hello:)</div>

The problem is there are too many of special characters and I'm wondering what is the be most efficient way to accomplish this?

EDIT:

String.Replace will not do my work and using Regex for parsing HTML is not really good approach.

By dislikes on this quetion there propably isn't any clean solution therefore I decided go for following algorithm:

1. create txt file with valid HTML special characters (like ¶)
2. parse file into array of string
3. Thanks to HtmLAgilityPack parse HTML and get raw text and replace all entities.

I know that this is not really effective for big html string but it should do the work for now.

Answer 1

You can try:

        string str = "<div>&gt;hello&lt;</div>";
        string output = Regex.Replace(str, "&gt;|&lt;", ":)");

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You can also use HtmlDecode

        string str = "<div>&gt;hello&lt;</div>";
        string output = WebUtility.HtmlDecode(str);