Download list of files from virtual directory?

Hi,
I am trying to download list of from download using bellow code
string source =@"http://172.27.0.173/TestEntry/Test_Files/021315-01/FinalFiles";
string[] PFiles = System.IO.Directory.GetFiles(source);
but here  I am getting error in the path 'http://172.27.0.173/TestEntry/Test_Files/021315-01/FinalFiles'  Is not a valid virtual path
URI formats are not supported.
Please help me