Regular Expressions

Regex regex = new Regex(@"(^[\40-\176]{1,254}$)");//Printable ASCII characters only
Match match = regex.Match(value);
if (match.Groups.Count == 2)
{
    host = match.Groups[1].Value;
}
else
{
    throw new InvalidOperationException(string.Format("The string {0} for host is misformatted. It may only contain printable US-ASCII characters.", value));
}

if (value == null)
{
    throw new ArgumentNullException("value");
}
if (value.Length < 1 || value.Length > 254)
{
    throw new ArgumentException("The host must be between 1 and 254 characters long.", "value");
}
if (Regex.IsMatch(value, "[^\40-\176]"))
{
    throw new InvalidOperationException(string.Format("The string {0} for host is misformatted. It may only contain printable US-ASCII characters.", value));
}

host = value;

Richard Deeming wrote:

I'd be inclined to move the length test out of the Regex,

Dim andSeparators() As String = {" and "}
Dim andTerms() as String
andTerms = String.Split(andSeparators, query)

"(\w+=\w+|\s(or|and)\s)"

Regex.IsMatch(inputStr, "^(\w+=\w+|\s(or|and)\s)+$");

Regex.IsMatch(inputStr, "^(\w+=\w+|(?<=\w+=\w+)\s(or|and)\s(?=\w+=\w+))+$");

Anchors in Regular Expressions : Word Boundary[^]

The \b anchor specifies that the match must occur on a boundary between a word character (the \w language element) and a non-word character (the \W language element). Word characters consist of alphanumeric characters and underscores; a non-word character is any character that is not alphanumeric or an underscore. The match may also occur on a word boundary at the beginning or end of the string.

((?<=\W)|^)%\s+\bcomplete\b

%\scomplete

%\s\bcomplete\b