C# - Validating Website URLs. IsWellFormedUriString always returning true

Question

I need a check that returns true for the following website urls: I need to make sure that websites that start as www. pass as true. Also google.com should return true.

www.google.com

google.com

http://google.com

http://www.google.com

https://google.com

https://www.google.com

I have been using IsWellFormedUriString and haven't gotten anywhere. It keeps returning true. I also have used Uri.TryCreate and can't get it to work either. There is so much on Stack Overflow regarding this topic but none of them are working. I must be doing something wrong.

Here is my ValidateUrl function:

   public static bool ValidateUrl(string url)
   {
       try
       {
           if (url.Substring(0, 3) != "www." && url.Substring(0, 4) != "http" && url.Substring(0, 5) != "https")
           {
               url = "http://" + url;
           }
           if (Uri.IsWellFormedUriString(url, UriKind.RelativeOrAbsolute))
           {
               Uri strUri = new Uri(url);
               return true;
           }
           else
           {
               return false;
           }
       }
       catch (Exception exc)
       {
           throw exc;
       }
   }

And I am calling it like this:

if (ValidateUrl(url) == false) { 
    validationErrors.Add(new Error() 
    { 
        fieldName = "url", 
        errorDescription = "Url is not in correct format." 
    }); 
}

It is returning true for htp:/google.com. I know there's a lot on this site regarding this topic but I have been trying to get this to work all day yesterday and nothing is working.

Answer 1

I got it working by writing a small helper method that uses Regex to validate the url.

The following URL's pass:

google.com

www.google.com

http://google.com

http://www.google.com

https://google.com/test/test

https://www.google.com/test

It fails on:

www.google.com/a bad path with white space/

Below is the helper method I created:

    public static bool ValidateUrl(string value, bool required, int minLength, int maxLength)
    {
        value = value.Trim();
        if (required == false && value == "") return true;
        if (required && value == "") return false;

        Regex pattern = new Regex(@"^(?:http(s)?:\/\/)?[\w.-]+(?:\.[\w\.-]+)+[\w\-\._~:/?#[\]@!\$&'\(\)\*\+,;=.]+$");
        Match match = pattern.Match(value);
        if (match.Success == false) return false;
        return true;
    }

This allows users to input any valid url, plus it accounts for bad url paths with white space which is exactly what I needed.