How to Check That a Uri String Is Valid

How to check that a uri string is valid

A well-formed URI implies conformance with certain RFCs. The local path in your example is not conformant with these. Read more in the IsWellFormedUriString documentation.

A false result from that method does not imply that the Uri class will not be able to parse the input. While the URI input might not be RFC conformant, it still can be a valid URI.

Update: And to answer your question - as the Uri documentation shows, there is a static method called TryCreate that will attempt exactly what you want and return true or false (and the actual Uri instance if true).

How to check whether a string is a valid HTTP URL?

Try this to validate HTTP URLs (uriName is the URI you want to test):

Uri uriResult;
bool result = Uri.TryCreate(uriName, UriKind.Absolute, out uriResult) 
    && uriResult.Scheme == Uri.UriSchemeHttp;

Or, if you want to accept both HTTP and HTTPS URLs as valid (per J0e3gan's comment):

Uri uriResult;
bool result = Uri.TryCreate(uriName, UriKind.Absolute, out uriResult) 
    && (uriResult.Scheme == Uri.UriSchemeHttp || uriResult.Scheme == Uri.UriSchemeHttps);

How to check whether a string is a valid url

I use this regex.

[-a-zA-Z0-9@:%._\+~#=]{2,256}\.[a-z]{2,6}\b([-a-zA-Z0-9@:%_\+.~#?&\/=]*)

Here's the regex in action with this question's url:

So if a match is found you got yourself a URL. And if in the future you need to get parts of it it can do that for you too.

Check if a JavaScript string is a URL

A related question with an answer

Or this Regexp from Devshed:

function validURL(str) {
  var pattern = new RegExp('^(https?:\\/\\/)?'+ // protocol
    '((([a-z\\d]([a-z\\d-]*[a-z\\d])*)\\.)+[a-z]{2,}|'+ // domain name
    '((\\d{1,3}\\.){3}\\d{1,3}))'+ // OR ip (v4) address
    '(\\:\\d+)?(\\/[-a-z\\d%_.~+]*)*'+ // port and path
    '(\\?[;&a-z\\d%_.~+=-]*)?'+ // query string
    '(\\#[-a-z\\d_]*)?$','i'); // fragment locator
  return !!pattern.test(str);
}

Dart / Flutter - Validating a string for URL

For some reason, the validators package is requiring a pretty recent version of flutter's testing library rather than leaving it up to the application. Maybe there's a good reason for that (i.e. they're using a new feature).

The flutter engine internally requires a particular version of the flutter_test library (which is why it's generally a bad idea to specify a version of it). So to fix this you'll have to upgrade your flutter by running flutter upgrade. If you're already at the most recent version of the channel you're in, you may have to run flutter channel dev or flutter channel master to switch to a channel (branch really) that's updated more often.

I run on the dev branch/channel for the most part and while it very occasionally has problems, it doesn't happen a lot. I'd advise against using the master branch if possible though.

Validating Uri from String

public static bool IsValidUri(string uriString)
{
    Uri uri;
    if (!uriString.Contains("://")) uriString = "http://" + uriString;
    if (Uri.TryCreate(uriString, UriKind.RelativeOrAbsolute, out uri))
    {
        if (Dns.GetHostAddresses(uri.DnsSafeHost).Length > 0)
        {
            return true;
        }
    }
    return false;
}

How to verify if a String in Java is a valid URL?

You can try to create a java.net.URL object out of it. If it is not a proper URL, a MalformedURLException will be thrown.

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