Hi nauna,
Use DirectoryInfo class.
C#
System.IO.DirectoryInfo info = new System.IO.DirectoryInfo(Server.MapPath("~/"));
System.IO.DirectoryInfo[] folders = info.GetDirectories();
VB.Net
Dim info As System.IO.DirectoryInfo = New System.IO.DirectoryInfo(Server.MapPath("~/"))
Dim folders As System.IO.DirectoryInfo() = info.GetDirectories()