Replace all & that are not a HTML entity using C#

Basically a dup of this question using php, but I need it for C#.

I need to be able to replace any & that is not currently not any HTML entity开发者_如何学C (e.g. &) before outputting to screen. I was thinking a regex, but I'm not sure if .Net has something built in that will do this.

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You can use HttpUtility.HtmlEncode.
Whithing the context of a page or UserControl, you can use Server.HtmlEncode.

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Better AntiXss.HtmlEncode, prevents XSS.

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You could always HTML Decode the string (which would turn any HTML symbols into their display equivalents), replace any &'s, and then Encode the string again (which turns the symbols back into what they were originally). You might need to watch for side effects though.