DownloadString value check for a if statement in c# : im new to c# so sorry in advance.

i am attempting to create a crawler that returns only links from a website and i have it to a point that it returns the htmlscript.
i am now wanting to use a if statement to check that the string is returned and if it is returned, it searches for all <a tags and shows me the href link.
but i dont know what object to check or what value i should be checking for.

here is what i have so far


        

        namespace crawler_pt._2
    {
        class Program
        {
            static void Main(string[] args)
            {
                System.Net.WebClient wc = new System.Net.WebClient();
                string WebData wc.DownloadString("https://www.abc.net.au/news/science/");
                Console.WriteLine(WebData);
            if 

        }
        
    }



