How To Collect All File Names From Remote Server In C#

I have many images on remote server say [URL] & i want to access file names of all files that resides in the folder 222 on [URL]

i have tried following code but getting error "virtual path is not valid" :

imageserver = http://images.foo.com/222;
DirectoryInfo di = new DirectoryInfo(imageserver); // line giving exception
FileInfo[] rgFiles = di.GetFiles();
string simagename = "";
if (rgFiles.Count() > 0)
{
foreach (FileInfo fi in rgFiles)
{
//collect each filename from here
}
}