C#: Removing common invalid characters from a string: improve this algorithm

Question

Consider the requirement to strip invalid characters from a string. The characters just need to be removed and replace with blank or string.Empty.

Answer 1

if you still want to do it in a LINQy way:

public static string CleanUp(this string orig)
{
    var badchars = new HashSet() { '!', '@', '#', '$', '%', '_' };

    return new string(orig.Where(c => !badchars.Contains(c)).ToArray());
}