Select substring after specific word

Question

From strings like this

<iframe width="560" height="315" src="https://www.youtube.com/embed/KRFHiBW9RE8" frameborder="0" allowfullscreen></iframe>

I need to select only the source, so the word between src="the string I need"

I have tried using IndexOf the word src=" but the link doesn't have a fixed number of characters to set the ending.

Answer 1

If you're trying to parse some HTML code - it might be better to use HTMLAgilityPack.

But in the case it is just some set of strings you've obtained from somewhere and want to parse - you can also do it using regular expressions:

string s ="<iframe width=\"560\" height=\"315\" src=\"https://www.youtube.com/embed/KRFHiBW9RE8\" frameborder=\"0\" allowfullscreen></iframe>";
var match = Regex.Match(s, "src=\"(.*?)\"");
string src;
if (match.Success)
    src = match.Groups[1].Value;

Answer 2

A naive implementation, in which I assume you have a string as input:

string input = "<iframe width=\"560\" height=\"315\" src=\"https://www.youtube.com/embed/KRFHiBW9RE8\" frameborder=\"0\" allowfullscreen></iframe>";

if (input.Contains("src=\""))
{
    string output = input.Substring(input.IndexOf("src=\"") + 5);
    // output is: https://www.youtube.com/embed/KRFHiBW9RE8" frameborder="0" allowfullscreen></iframe>

    output = output.Substring(0, output.IndexOf("\""));
    // output is: https://www.youtube.com/embed/KRFHiBW9RE8
}

It will certainly miss edge cases like src =", but will give you a place to start. Obviously this is also a problem which can be solved using regular expressions; I'll leave that for someone else to answer.

Answer 3

I'd be tempted to split all the properties out into an array as it's possible I might want some of the others later on as well. In doing this it would also allow easy access to the 'src' property. So I'd do something like this:

string iFrameString = "<iframe width=\"560\" height=\"315\" src=\"https://www.youtube.com/embed/KRFHiBW9RE8\" frameborder=\"0\" allowfullscreen>";

//split properties based on spaces
string[] tagProps = iFrameString.Split(new Char[]{' '});

//get the property out.
string prop = "src=\"";
string source = Array.Find(tagProps, x => x.StartsWith(prop, StringComparison.InvariantCultureIgnoreCase));

string ModifiedSource = source.Substring(prop.Length,source.Length - prop.Length);

The benefit of this is that you have all the other properties in your array as well and you could get those out if needed.