问如何让WebClient使用Cookie？

EN

Public Class CookieAwareWebClient
    Inherits WebClient

    Private cc As New CookieContainer()
    Private lastPage As String

    Protected Overrides Function GetWebRequest(ByVal address As System.Uri) As System.Net.WebRequest
        Dim R = MyBase.GetWebRequest(address)
        If TypeOf R Is HttpWebRequest Then
            With DirectCast(R, HttpWebRequest)
                .CookieContainer = cc
                If Not lastPage Is Nothing Then
                    .Referer = lastPage
                End If
            End With
        End If
        lastPage = address.ToString()
        Return R
    End Function
End Class

using System.Net;
class CookieAwareWebClient : WebClient
{
    private CookieContainer cc = new CookieContainer();
    private string lastPage;

    protected override WebRequest GetWebRequest(System.Uri address)
    {
        WebRequest R = base.GetWebRequest(address);
        if (R is HttpWebRequest)
        {
            HttpWebRequest WR = (HttpWebRequest)R;
            WR.CookieContainer = cc;
            if (lastPage != null)
            {
                WR.Referer = lastPage;
            }
        }
        lastPage = address.ToString();
        return R;
    }
}