Decode base 64 to Image url

Question

Hi guys I have script to encrypt url image to base64 like :

public String ConvertImageURLToBase64(String url)
{
StringBuilder _sb = new StringBuilder();
Byte[] _byte = this.GetImage(url);
_sb.Append(Convert.ToBase64String(_byte, 0, _byte.Length));
return _sb.ToString();
}
private 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);
}

Now I want to decode base64 to url image . is it possible? if possible can you give me reference, please? thanks. I am Mega