Compilation Error BC30451 from remote servier

[Amy Zhao]

Hi,

I get the mentioned compilation error after I deployed my website to
the host server. Everything works fine on my local machine. What is
the problem?? Any help is appreciated!!

BC30451: Name 'Directory' is not declared.

Line 10: Dim albumPath As String =
GetPath(PathTypes.Originals)
Line 11: If albumPath IsNot Nothing Then
Line 12: If Directory.GetDirectories(albumPath).Length > 0
Then
Line 13: 'Create the Jump To Album Menu
Line 14: _CurrentAlbum = Request.QueryString("cat")

Source File: c:\hosting\....\_Main.master.vb Line: 12