I don't think there is a built-in sanitizer for C# that you can use but here is what i did when i had the same issue. I used the HtmlAgilityPackSanitizerProvider which comes with AjaxControlToolkit. Code looks like this:
private static AjaxControlToolkit.Sanitizer.HtmlAgilityPackSanitizerProvider sanitizer = new AjaxControlToolkit.Sanitizer.HtmlAgilityPackSanitizerProvider();
private static Dictionary<string, string[]> elementWhitelist = new Dictionary<string, string[]>
{
{"b" , new string[] { "style" }},
{"strong" , new string[] { "style" }},
{"i" , new string[] { "style" }},
{"em" , new string[] { "style" }},
{"u" , new string[] { "style" }},
{"strike" , new string[] { "style" }},
{"sub" , new string[] { "style" }},
{"sup" , new string[] { "style" }},
{"p" , new string[] { "align" }},
{"div" , new string[] { "style", "align" }},
{"ol" , new string[] { }},
{"li" , new string[] { }},
{"ul" , new string[] { }},
{"a" , new string[] { "href" }},
{"font" , new string[] { "style", "face", "size", "color" }},
{"span" , new string[] { "style" }},
{"blockquote" , new string[] { "style", "dir" }},
{"hr" , new string[] { "size", "width", "id" }},
{"img" , new string[] { "src" }},
{"h1" , new string[] { "style" }},
{"h2" , new string[] { "style" }},
{"h3" , new string[] { "style" }},
{"h4" , new string[] { "style" }},
{"h5" , new string[] { "style" }},
{"h6" , new string[] { "style" }}
};
private static Dictionary<string, string[]> attributeWhitelist = new Dictionary<string, string[]>
{
{"style" , new string[] {}},
{"align" , new string[] {}},
{"href" , new string[] {}},
{"face" , new string[] {}},
{"size" , new string[] {}},
{"color" , new string[] {}},
{"dir" , new string[] {}},
{"width" , new string[] {}},
{"id" , new string[] {}},
{"src" , new string[] {}}
};
public string SanitizeHtmlInput(string unsafeStr)
{
return sanitizer.GetSafeHtmlFragment(unsafeStr, elementWhitelist, attributeWhitelist);
}
Hope this helps.