how to protect from injection (javascript)?

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C#

ASP.NET

C#4.0

haii.. i want to ask something,,

how to protect from injection using javascript,,example like a forum or blog post.

if someone post comment using javascript like this: <script>alert('boo!!')</script>

i have try to save comment using example HttpUtility.HtmlEncode(body);

and i show to listview, example HttpUtility.HtmlDecode(body);

somebody help me..??