返回bool值:

Uri.IsWellFormedUriString(a.GetAttribute("href"), UriKind.Absolute)

此方法在http和https中都可以正常工作。只有一行:)

if (Uri.IsWellFormedUriString("https://www.google.com", UriKind.Absolute))

MSDN: IsWellFormedUriString

我创建了这个函数来帮助我进行URL验证，你可以根据自己的喜好定制它，注意这是用python3.10.6编写的

def url_validator(url: str) -> bool:
    """
    use this func to filter out the urls to follow only valid urls
    :param: url
    :type: str
    :return: True if the passed url is valid otherwise return false
    :rtype: bool
    """

    #the following regex is copied from Django source code 
    # to validate a url using regax
    
    regex = re.compile(
        r"^(?:http|ftp)s?://"  # http:// or https://
        r"(?:(?:[A-Z0-9](?:[A-Z0-9-]{0,61}[A-Z0-9])?\.)+(?:[A-Z]{2,6}\.?|[A-Z0-9-]{2,}\.?)|"  # domain...
        r"localhost|"  # localhost...
        r"\d{1,3}\.\d{1,3}\.\d{1,3}\.\d{1,3})"  # ...or ip
        r"(?::\d+)?"  # optional port
        r"(?:/?|[/?]\S+)$",
        re.IGNORECASE,
    )


    blocked_sites: list[str] = []

    for site in blocked_sites:
        if site in url or site == url:
            return False

    # if none of the above then ensure that the url is valid and then return True otherwise return False
    if re.match(regex, url):
        return True

    return False

作为使用正则表达式的另一种方法，这段代码使用Uri。TryCreate每个OP，但也检查结果，以确保它的Scheme是http或https之一:

bool passed =
  Uri.TryCreate(url, UriKind.Absolute, out Uri uriResult)
    && (uriResult.Scheme == Uri.UriSchemeHttp
      || uriResult.Scheme == Uri.UriSchemeHttps);

这里的所有答案要么允许使用其他方案的url(例如，file://， ftp://))，要么拒绝以http://或https://开头的人类可读的url(例如，www.google.com)，这在处理用户输入时并不好。

我是这样做的:

public static bool ValidHttpURL(string s, out Uri resultURI)
{
    if (!Regex.IsMatch(s, @"^https?:\/\/", RegexOptions.IgnoreCase))
        s = "http://" + s;

    if (Uri.TryCreate(s, UriKind.Absolute, out resultURI))
        return (resultURI.Scheme == Uri.UriSchemeHttp || 
                resultURI.Scheme == Uri.UriSchemeHttps);

    return false;
}

用法:

string[] inputs = new[] {
                          "https://www.google.com",
                          "http://www.google.com",
                          "www.google.com",
                          "google.com",
                          "javascript:alert('Hack me!')"
                        };
foreach (string s in inputs)
{
    Uri uriResult;
    bool result = ValidHttpURL(s, out uriResult);
    Console.WriteLine(result + "\t" + uriResult?.AbsoluteUri);
}

输出:

True    https://www.google.com/
True    http://www.google.com/
True    http://www.google.com/
True    http://google.com/
False

返回bool值:

Uri.IsWellFormedUriString(a.GetAttribute("href"), UriKind.Absolute)