I recently had need to break a URL down to it’s component pieces so that I could use just those parts that I needed at different times. My initial approach to solving this problem was to Google for a built in solution to parsing URLs in C# but I couldn’t find one. So then I feel back to a RegEx pattern. .Net in general has some nice regex features (including being able to name groups) and so this is the RegEx I came up with (after looking at some others that already existed):

private static Regex pattern = new Regex("(?<protocol>http(s)?|ftp)://(?

However, that RegEx has a problem where it won’t get the full Port number if the port is immediately followed by a query like so: http://my.domain.com:8000?arg1=this&arg2=that

Instead of returning the port of 8000 the regex ends up with the port of 8. That sucks. Fortunately, I know someone else who I could ask about it and he pointed me at the useful built in C# library : System.Uri.

Why this library didn’t pop up in my Google queries I don’t know but, let me tell you, it does pretty much everything I need. However, I do have one minor quibble. The protocol portion of the URL is parsed out and identified by Scheme.

Now, with a string based representation of a URL I can break it down quickly using the System.URI class. Lets say you want to get the port:

string url = "http://my.domain.com:8000?arg1=this&amp;arg2=that";
System.Uri uri = new System.Uri(url);

// get the port
int port = uri.Port;

// get the host name (my.domain.com)
string host = uri.Host;

// get the protocol
string protocol = uri.Scheme;

// get everything before the query:
string cleanURL = uri.Scheme + "://" +
uri.GetComponents(UriComponents.HostAndPort, UriFormat.UriEscaped);

As you can imagine there is actually a lot you can do. If you don’t think you can find a bit from the URL check out that uri.GetComponents method - the UriComponents enumeration has a bunch of options you can dig into!