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How to Extract Domain name from string with Regex in C#?

I want extract Top-Level Domain names and Country top-level domain names from string with Regex. I tested many Regex like this code:
var linkParser = new Regex(#"\b(?:https?://|www\.)\S+\b", RegexOptions.Compiled | RegexOptions.IgnoreCase);
Match m = linkParser.Match(Url);
Console.WriteLine(m.Value);
But none of these codes could do it properly.
The text string entered by the user can be in the following statements:
jonasjohn.com
http://www.jonasjohn.de/snippets/csharp/
jonasjohn.de
www.jonasjohn.de/snippets/csharp/
http://www.answers.com/article/1194427/8-habits-of-extraordinarily-likeable-people
http://www.apple.com
https://www.cnn.com.au
http://www.downloads.news.com.au
https://ftp.android.co.nz
http://global.news.ca
https://www.apple.com/
https://ftp.android.co.nz/
http://global.news.ca/
https://www.apple.com/
https://johnsmith.eu
ftp://johnsmith.eu
johnsmith.gov.ae
johnsmith.eu
www.jonasjohn.de
www.jonasjohn.ac.ir/snippets/csharp
http://www.jonasjohn.de/
ftp://www.jonasjohn.de/
https://subdomain.abc.def.jonasjohn.de/test.htm
The Regex I tested:
^(?:https?:\/\/)?(?:[^#\/\n]+#)?(?:www\.)?([^:\/\n]+)"
\b(?:https?://|www\.)\S+\b
://(?<host>([a-z\\d][-a-z\\d]*[a-z\\d]\\.)*[a-z][-a-z\\d]+[a-z])
and also too many
I just need the domain name and I don't need a protocol or a subdomain.
Like:
Domainname.gTLD or DomainName.ccTLD or DomainName.xyz.ccTLD
I got list of them from PUBLIC SUFFIX
Of course, I've seen a lot of posts on stackoverflow.com, but none of it answered me.

You don't need a Regex to parse a URL. If you have a valid URL, you can use one of the Uri constructors or Uri.TryCreate to parse it:
if(Uri.TryCreate("http://google.com/asdfs",UriKind.RelativeOrAbsolute,out var uri))
{
Console.WriteLine(uri.Host);
}
www.jonasjohn.de/snippets/csharp/ and jonasjohn.de/snippets/csharp/ aren't valid URLs though. TryCreate can still parse them as relative URLs, but reading Host throws System.InvalidOperationException: This operation is not supported for a relative URI.
In that case you can use the UriBuilder class, to parse and modify the URL eg:
var bld=new UriBuilder("jonasjohn.com");
Console.WriteLine(bld.Host);
This prints
jonasjohn.com
Setting the Scheme property produces a valid,complete URL:
bld.Scheme="https";
Console.WriteLine(bld.Uri);
This produces:
https://jonasjohn.com:80/

According to Lidqy answer, I wrote this function, which I think supports most possible situations, and if the input value is out of this, you can make it an exception.
public static string ExtractDomainName(string Url)
{
var regex = new Regex(#"^((https?|ftp)://)?(www\.)?(?<domain>[^/]+)(/|$)");
Match match = regex.Match(Url);
if (match.Success)
{
string domain = match.Groups["domain"].Value;
int freq = domain.Where(x => (x == '.')).Count();
while (freq > 2)
{
if (freq > 2)
{
var domainSplited = domain.Split('.', 2);
domain = domainSplited[1];
freq = domain.Where(x => (x == '.')).Count();
}
}
return domain;
}
else
{
return String.Empty;
}
}

var rx = new Regex(#"^((https?|ftp)://)?(www\.)?(?<domain>[^/]+)(/|$)");
var data = new[] { "jonasjohn.com",
"http://www.jonasjohn.de/snippets/csharp/",
"jonasjohn.de",
"www.jonasjohn.de/snippets/csharp/",
"http://www.answers.com/article/1194427/8-habits-of-extraordinarily-likeable-people",
"http://www.apple.com",
"https://www.cnn.com.au",
"http://www.downloads.news.com.au",
"https://ftp.android.co.nz",
"http://global.news.ca",
"https://www.apple.com/",
"https://ftp.android.co.nz/",
"http://global.news.ca/",
"https://www.apple.com/",
"https://johnsmith.eu",
"ftp://johnsmith.eu",
"johnsmith.gov.ae",
"johnsmith.eu",
"www.jonasjohn.de",
"www.jonasjohn.ac.ir/snippets/csharp",
"http://www.jonasjohn.de/",
"ftp://www.jonasjohn.de/",
"https://subdomain.abc.def.jonasjohn.de/test.htm"
};
foreach (var dat in data) {
var match = rx.Match(dat);
if (match.Success)
Console.WriteLine("{0} => {1}", dat, match.Groups["domain"].Value);
else {
Console.WriteLine("{0} => NO MATCH", dat);
}
}

Extract ID and replace everything in `Example HTML`

New to Regular Expressions, I want to have the following text in my HTML and would like to replace with something else
Example HTML:
{{Object id='foo'}}
Extract the id into a variable like this:
string strId = "foo";
So far I have the following Regular Expression code that will capture the Example HTML:
string strStart = "Object";
string strFind = "{{(" + strStart + ".*?)}}";
Regex regExp = new Regex(strFind, RegexOptions.IgnoreCase);
Match matchRegExp = regExp.Match(html);
while (matchRegExp.Success)
{
//At this point, I have this variable:
//{{Object id='foo'}}
//I can find the id='foo' (see below)
//but not sure how to extract 'foo' and use it
string strFindInner = "id='(.*?)'"; //"{{Slider";
Regex regExpInner = new Regex(strFindInner, RegexOptions.IgnoreCase);
Match matchRegExpInner = regExpInner.Match(matchRegExp.Value.ToString());
//Do something with 'foo'
matchRegExp = matchRegExp.NextMatch();
}
I understand this might be a simple solution, I am hoping to gain more knowledge about Regular Expressions but more importantly, I am hoping to receive a suggestion on how to approach this cleaner and more efficiently.
Thank you
Edit:
Is this an example that I could potentially use: c# regex replace

While I am not solving my initial question with Regular Expressions, I did move into a simpler solution using SubString, IndexOf and string.Split for the time being, I understand that my code needs to be cleaned up but thought I would post the answer that I have thus far.
string html = "<p>Start of Example</p>{{Object id='foo'}}<p>End of example</p>"
string strObject = "Slider"; //Example
//When found, this will contain "{{Object id='foo'}}"
string strCode = "";
//ie: "id='foo'"
string strCodeInner = "";
//Tags will be a list, but in this example, only "id='foo'"
string[] tags = { };
//Looking for the following "{{Object "
string strFindStart = "{{" + strObject + " ";
int intFindStart = html.IndexOf(strFindStart);
//Then ending in the following
string strFindEnd = "}}";
int intFindEnd = html.IndexOf(strFindEnd) + strFindEnd.Length;
//Must find both Start and End conditions
if (intFindStart != -1 && intFindEnd != -1)
{
strCode = html.Substring(intFindStart, intFindEnd - intFindStart);
//Remove Start and End
strCodeInner = strCode.Replace(strFindStart, "").Replace(strFindEnd, "");
//Split by spaces, this needs to be improved if more than IDs are to be used
//but for proof of concept this is perfect
tags = strCodeInner.Split(new char[] { ' ' });
}
Dictionary<string, string> dictTags = new Dictionary<string, string>();
foreach (string tag in tags)
{
string[] tagSplit = tag.Split(new char[] { '=' });
dictTags.Add(tagSplit[0], tagSplit[1].Replace("'", "").Replace("\"", ""));
}
//At this point, I can replace "{{Object id='foo'}}" with anything I'd like
//What I don't show is that I go into the website's database,
//get the object (ie: Slider) and return the html for slider with the ID of foo
html = html.Replace(strCode, strView);
/*
"html" variable may contain:
<p>Start of Example</p>
<p id="foo">This is the replacement text</p>
<p>End of example</p>
*/

The fastest way to trim string in C#

I need to trim paths in million strings like this:
C:\workspace\my_projects\my_app\src\my_component\my_file.cpp
to
src\my_component\my_file.cpp
I.e. remove absolute part of the path, what is the fastest way to do that?
My try using regex:
Regex.Replace(path, #"(.*?)\src", ""),

I wouldn't go with regex for this, use the plain old method.
If the path prefix is always the same:
const string partToRemove = #"C:\workspace\my_projects\my_app\";
if (path.StartsWith(partToRemove, StringComparison.OrdinalIgnoreCase))
path = path.Substring(partToRemove.Length);
If the prefix is variable, you can get the last index of \src\:
var startIndex = path.LastIndexOf(#"\src\", StringComparison.OrdinalIgnoreCase);
if (startIndex >= 0)
path = path.Substring(startIndex + 1);

define the regex with a new and reuse it
there is a (significant) cost to creating the regex
string input = "This is text with far too much " +
"whitespace.";
string pattern = "\\s+";
string replacement = " ";
Regex rgx = new Regex(pattern);
string result = rgx.Replace(input, replacement);

I'm not sure if you need speed here, but if you always get the full path, you could do a simple .Substring()
var path = #"C:\workspace\my_projects\my_app\src\my_component\my_file.cpp";
Console.WriteLine(path.Substring(32));
However, I think you should sanitize your input first; in this case, the Uri class could do the parsing step:
var root = #"C:\workspace\my_projects\my_app\";
var path = #"C:\workspace\my_projects\my_app\src\my_component\my_file.cpp";
var relative = new Uri(root).MakeRelativeUri(new Uri(path));
Console.WriteLine(relative.OriginalString.Replace("/", "\\"));
Notice here the Uri will change the \ with a /: that's the .Replace reason.

Cant think any faster than this
path.Substring(33);
What is before src is constant. and it starts from index 33.
C:\workspace\my_projects\my_app\src\my_component\my_file.cpp
^
How ever if its not always constant. you can find it once. and do the rest inside loop.
int startInd = path.IndexOf(#"\src\") + 1;
// Do this inside loop. 1 million times
path.Substring(startInd);

If your files will all end in "src/filename.ext" you could use the Path class in the .NET framework for it and get around all caveats you could have with pathes and filenames:
result = "src\" + Path.GetFileName(path);
So you should first double-check that the conversion is the thing that takes to long.

Parsing Image Path in ImageResizer

I'm resizing an image dynamically thus:
ImageJob i = new ImageJob(file, "~/eventimages/<guid>_<filename:A-Za-z0-9>.<ext>",
new ResizeSettings("width=200&height=133&format=jpg&crop=auto"));
i.Build();
I'm attempting to store the image relative URL in the DB. The i.FinalPath property gives me:
C:\inetpub\wwwroot\Church\eventimages\56b640bff5ba43e8aa161fff775c5f97_scenery.jpg
How can I obtain just the image filename - best way to parse this?
Desired string: /eventimages/56b640bff5ba43e8aa161fff775c5f97_scenery.jpg

something like below,
var sitePath = MapPath(#"~");
var relativePath= i.FinalPath.Replace(sitePath, "~");

Just use Regular expressions
Regex.Match
Create you pattern and extract desired value
string input = "C:\\inetpub\\wwwroot\\Church\\eventimages\\56b640bff5ba43e8aa161fff775c5f97_scenery.jpg";
Match match = Regex.Match(input, #"^C:\\[A-Za-z0-9_]+\\[A-Za-z0-9_]+\\[A-Za-z0-9_]+\\([A-Za-z0-9_]+\\[A-Za-z0-9_]+\.jpg)$", RegexOptions.IgnoreCase);
if (match.Success)
{
// Finally, we get the Group value and display it.
string path = match.Groups[1].Value.Replace("\\", "/");
}

Here is what I use in a utility method:
Uri uri1 = new Uri(i.FinalPath);
Uri uri2 = new Uri(HttpContext.Current.Server.MapPath("/"));
Uri relativeUri = uri2.MakeRelativeUri(uri1);
(stolen from someone else... can't remember who, but thanks)

Regex required for renaming file in C#

I need a regex for renaming file in c#. My file name is 22px-Flag_Of_Sweden.svg.png. I want it to rename as sweden.png.
So for that I need regex. Please help me.
I have various files more than 300+ like below:
22px-Flag_Of_Sweden.svg.png - should become sweden.png
13px-Flag_Of_UnitedStates.svg.png - unitedstates.png
17px-Flag_Of_India.svg.png - india.png
22px-Flag_Of_Ghana.svg.png - ghana.png
These are actually flags of country. I want to extract Countryname.Fileextension. Thats all.

var fileNames = new [] {
"22px-Flag_Of_Sweden.svg.png"
,"13px-Flag_Of_UnitedStates.svg.png"
,"17px-Flag_Of_India.svg.png"
,"22px-Flag_Of_Ghana.svg.png"
,"asd.png"
};
var regEx = new Regex(#"^.+Flag_Of_(?<country>.+)\.svg\.png$");
foreach ( var fileName in fileNames )
{
if ( regEx.IsMatch(fileName))
{
var newFileName = regEx.Replace(fileName,"${country}.png").ToLower();
//File.Save(Path.Combine(root, newFileName));
}
}

I am not exactly sure how this would look in c# (although the regex is important and not the language), but in Java this would look like this:
String input = "22px-Flag_Of_Sweden.svg.png";
Pattern p = Pattern.compile(".+_(.+?)\\..+?(\\..+?)$");
Matcher m = p.matcher(input);
System.out.println(m.matches());
System.out.println(m.group(1).toLowerCase() + m.group(2));
Where the relevant for you is this part :
".+_(.+?)\\..+?(\\..+?)$"
Just concat the two groups.
I wish I knew a bit of C# right now :)
Cheers Eugene.

This will return country in the first capture group: ([a-zA-Z]+)\.svg\.png$

I don't know c# but the regex could be:
^.+_(\pL+)\.svg\.png
and the replace part is : $1.png