problem with asp.net dialogbox with open saveas cancel

 Hi,
i am having a problem with dialog box.when i am using a file system object for opening a dialog box
and when clicking on open it is giving error that file not found actually it is reading file path from temp folder and i have given path for my directory

here's my code

1- when i am using file system object, i am giving my path and when i am clicking on open
        then it is not opening the file and picking path from temp  folder


    Dim filePath As String = Server.MapPath("~/Depot/Utilities/AutLmt/auto.txt")
        Dim targetFile As System.IO.FileInfo = New System.IO.FileInfo(filePath)

        If targetFile.Exists Then

         Response.Clear()
             Res ...