using System;

using System.IO;

using System.Text;

using System.Net;

public class Program

{

    // Referance - https://gist.github.com/malkitsingh/a3629a71ed6c50fcde6c 

    public static void Main()

    {

        var URL = "https://dummyimage.com/600x400/000/fff&text=Rahul";

        var data = ConvertImageURLToBase64(URL);

        Console.WriteLine(data);

    }

    public static String ConvertImageURLToBase64(String url)

    {

         StringBuilder _sb = new StringBuilder();

​

         Byte[] _byte = GetImage(url);

​

         _sb.Append(Convert.ToBase64String(_byte, 0, _byte.Length));

​

         return _sb.ToString();

    }

​

    private static byte[] GetImage(string url)

    {

         Stream stream = null;

         byte[] buf;

​

         try

         {

              WebProxy myProxy = new WebProxy();

              HttpWebRequest req = (HttpWebRequest)WebRequest.Create(url);

​

              HttpWebResponse response = (HttpWebResponse)req.GetResponse();

              stream = response.GetResponseStream();

​

              using (BinaryReader br = new BinaryReader(stream))

              {

                   int len = (int)(response.ContentLength);

                   buf = br.ReadBytes(len);

                   br.Close();

              }

​

              stream.Close();

              response.Close();

         }

         catch (Exception exp)

         {

              buf = null;

         }

​

         return (buf);

    }

}