我遇到了类似的问题,根据前面的答案,写了这个扩展方法。最重要的是,它采用定义“根”域的参数,即方法的使用者认为是根的任何参数。在 OP 的情况下,调用将是
Uri uri = "foo.bar.car.com.au";
uri.DnsSafeHost.GetSubdomain("car.com.au"); // returns foo.bar
uri.DnsSafeHost.GetSubdomain(); // returns foo.bar.car
这是扩展方法:
/// <summary>Gets the subdomain portion of a url, given a known "root" domain</summary>
public static string GetSubdomain(this string url, string domain = null)
{
var subdomain = url;
if(subdomain != null)
{
if(domain == null)
{
// Since we were not provided with a known domain, assume that second-to-last period divides the subdomain from the domain.
var nodes = url.Split('.');
var lastNodeIndex = nodes.Length - 1;
if(lastNodeIndex > 0)
domain = nodes[lastNodeIndex-1] + "." + nodes[lastNodeIndex];
}
// Verify that what we think is the domain is truly the ending of the hostname... otherwise we're hooped.
if (!subdomain.EndsWith(domain))
throw new ArgumentException("Site was not loaded from the expected domain");
// Quash the domain portion, which should leave us with the subdomain and a trailing dot IF there is a subdomain.
subdomain = subdomain.Replace(domain, "");
// Check if we have anything left. If we don't, there was no subdomain, the request was directly to the root domain:
if (string.IsNullOrWhiteSpace(subdomain))
return null;
// Quash any trailing periods
subdomain = subdomain.TrimEnd(new[] {'.'});
}
return subdomain;
}