Someone at Microsoft has posted improved versions of HtmlEncode and UrlEncode in what they call the "Microsoft Anti-Cross Site Scripting Library V1.0." The library includes two methods that are essentially the same as the corresponding methods in HtmlServerUtility:public static string HtmlEncode(string s);
public static string UrlEncode(string s);
Thus:String s = Microsoft.Security.Application.AntiXSSLibrary.HtmlEncode(TextBox1.Text);
The difference between the HtmlUtility and the Anti-XSS library versions of the methods is that the former encodes only a specific a set of characters, whereas the new version encodes everything but a specific set of characters. IOW, the former uses a blacklist, the latter a whitelist. In security terms, this means the new version is that much harder to get around.
(All of this information lifted directly from the docs and samples included with the library.)
To use the new library, download the .msi from the download page and run it. The installer puts the library by default at x:\Program Files\microsoft\Anti-Cross Site Scripting Library V1.0. The installation includes some minimal docs, some samples, and an assembly containing the class. The easiest way to use it, probably, is to copy the assembly to the Bin folder of any app where you want to use it. Have a look at the .rtf file in the Documentation folder for a little more information than what's listed here.
Via Mike Gunderloy.