Regular Expressions

^((\\b[^\\s=]+)=(([^=]|\\\\=)+))*$

^((?<key>\b[^\s=]+)=(?<value>([^=]|\\=)+))+$

(\w+(?=\=))|((?<!\\)(?<=\=)(.+?)((?=(\s\w+\=))|$))

([\x20-\x7e])

set
{
    host = Regex.Replace(value, @"[^\x20-\x7e]", string.Empty);
}

set
{
    if (!string.IsNullOrEmpty(value))
    {
        char[] validChars = new char[value.Length];
        int validCharIndex = 0;
        
        foreach (char c in value)
        {
            if ('\x20' <= c && c <= '\x7e')
            {
                validChars[validCharIndex] = c;
                validCharIndex++;
            }
        }
        
        if (validCharIndex == 0)
        {
            value = string.Empty;
        }
        else if (validCharIndex != value.Length)
        {
            value = new string(validChars, 0, validCharIndex);
        }
    }
    
    host = value;
}

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+))+$");