static extern bool SetCurrentDirectory(string lpPathName);

Private Shared Function SetCurrentDirectory(lpPathName As String) As Boolean

Directory.SetCurrentDirectory

static extern bool FtpSetCurrentDirectory(IntPtr hFtpConnection, string lpszDirectory);

Declare Function FtpSetCurrentDirectory Lib "wininet.dll" Alias "FtpSetCurrentDirectoryA" (ByVal hConnect As IntPtr, ByVal lpszDirectory As String) As Boolean

Dim changed As Boolean = FtpSetCurrentDirectory(hINetConn, changePath)

System.IO.Directory.SetCurrentDirectory (currentDirectory);