Validate Format of a Domain Name

originally posted 2014-07-22

1	originally posted 2014-07-22

public static bool IsValidDomainName(string name, out string formatMessage)
{
    /*
    http://en.wikipedia.org/wiki/Domain_Name_System
    Each label may contain up to 63 characters
    The characters allowed in a label are a subset of the ASCII character set, and includes the characters a through z, A through Z, digits 0 through 9, and the hyphen. 
    This rule is known as the LDH rule (letters, digits, hyphen). Domain names are interpreted in case-independent manner.
    Labels may not start or end with a hyphen. 
    */
    formatMessage = "Up to 64 letters, digits or hyphens. Cannot start or end with a hyphen.";

    if (name == null) return false;
    return Regex.IsMatch(name, @"(^[a-zA-Z0-9][a-zA-Z0-9\-]{0,61}[a-zA-Z0-9]{0,1}$)");
}

public static bool IsValidDomainName(string name, out string formatMessage)

{

http://en.wikipedia.org/wiki/Domain_Name_System

Each label may contain up to 63 characters

The characters allowed in a label are a subset of the ASCII character set, and includes the characters a through z, A through Z, digits 0 through 9, and the hyphen.

This rule is known as the LDH rule (letters, digits, hyphen). Domain names are interpreted in case-independent manner.

Labels may not start or end with a hyphen.

formatMessage = "Up to 64 letters, digits or hyphens. Cannot start or end with a hyphen.";

if (name == null) return false;

return Regex.IsMatch(name, @"(^[a-zA-Z0-9][a-zA-Z0-9\-]{0,61}[a-zA-Z0-9]{0,1}$)");

}