Problem with Regex.Match vs Regex.IsMatch

Question

Hello, i'm trying to replace a text which contains url's with the text with the tags and i'm trying to use something like this, but i just don't get why this is not working, maybe i'm too tired too see it. Here goes my test:

 [Test]
 public void Check() {
  string expUrl = @"^(https?://)"
  + @"?(([0-9a-z_!~*'().&=+$%-]+: )?[0-9a-z_!~*'().&=+$%-]+@)?" //user@
  + @"(([0-9]{1,3}\.){3}[0-9]{1,3}" // IP- 199.194.52.184
  + @"|" // allows either IP or domain
  + @"([0-9a-z_!~*'()-]+\.)*" // tertiary domain(s)- www.
  + @"([0-9a-z][0-9a-z-]{0,61})?[0-9a-z]" // second level domain
  + @"(\.[a-z]{2,6})?)" // first level domain- .com or .museum is optional
  + @"(:[0-9]{1,5})?" // port number- :80
  + @"((/?)|" // a slash isn't required if there is no file name
  + @"(/[0-9a-z_!~*'().;?:@&=+$,%#-]+)+/?)$"; 

  const string url = "http://www.google.com";

  var b = Regex.IsMatch(url, expUrl);
  Assert.IsTrue(b);

  var text = string.Format("this is a link... {0} end of link", url);
  var resul = Regex.Match(text, expUrl);
  Assert.IsTrue(resul.Success);
 }

Why the url variable passes the IsMatch Check, but doesn't pass the Match check? thanks in advance.

Answer 1

Because you started your regex with ^ and ended with $. Those specify that the match must begin at the start of the string and end at the end. Since your match is in the middle, it was not found.

Answer 2

Because your regular expression begins with a "^" character.. indicating that "https" should go FIRST, as well as the $ indicating that the string should end with the last defined group.

if you remove ^ and $, both tests will pass

Answer 3

^(https?://)

You're requiring it to start with http

Update this line from

string expUrl = @"^(https?://)"

to

string expUrl = @"(https?://)"

And update your final line from

+ @"(/[0-9a-z_!~*'().;?:@&=+$,%#-]+)+/?)$";

to

+ @"(/[0-9a-z_!~*'().;?:@&=+$,%#-]+)+/?)";