C#

Regex to remove HTML tags including special characters like  

public static string StripHtmlTags(this string source)
{
    return Regex.Replace(source, "<.*?>|&.*?;", string.Empty);
}

Extension method to AddRange to IList<T> interface

public static void AddRange(this IList iList, IEnumerable collection)
{
    foreach (var item in collection)
    {
        iList.Add(item);
    }
}