使用 WebRequest.Create(URL) 调用页面时无法检索会话值

Question

我有一个页面 (email.aspx) 正在检索会话值并根据该值进行一些处理。

当我使用其 URL 直接从浏览器调用 email.ASPX 时，一切正常，没有任何问题。

Public Sub Page_Load(ByVal sender As Object, ByVal e As System.EventArgs) Handles Me.Load

        Dim emailaddress As String
        Dim x As String = ""
        x = Session("id")
        If x = "" Then
            emailaddress = "failed to get session"
        Else

            ' Do some staff here
        End If

        Response.Write(emailaddress)


    End Sub

但是当我尝试使用 WebRequest.Create(URL) 从另一个包含嵌入式 vb.net 代码的 ASPX 页面调用 (email.aspx) 时，我发现它无法检索导致错误的 Session 值！

Public Function getemailaddress() As String

        Dim sURL As String
        sURL = "http://sample/email.aspx"

        Dim wrGETURL As System.Net.WebRequest
        wrGETURL = System.Net.WebRequest.Create(sURL)


        Dim emailaddress As String
        Dim objStream As System.Net.HttpWebResponse
        objStream = wrGETURL.GetResponse

        If objStream.StatusCode = System.Net.HttpStatusCode.OK Then
            Dim responseStream As System.IO.StreamReader
            responseStream = New System.IO.StreamReader(objStream.GetResponseStream())
            emailaddress = responseStream.ReadToEnd()
        End If
        objStream.Close()


        Return emailaddress

    End Function

我无法弄清楚这个问题背后的原因

Answer 1

客户端的会话标识符存储在 cookie 中。 WebRequest 仅在 当前 请求存在期间存储其 cookie，然后将其删除。您需要创建一个“全局”CookieContainer 并将其传递给您发出的网络请求，以便在不同请求之间共享 cookie。

根据您在多少个不同的地方提出请求，您可能希望将其作为参数传递给您的函数：

Public Function getemailaddress(ByVal Cookies As System.Net.CookieContainer) As String

    ...your code...

    'We need to cast wrGETURL to a HttpWebRequest.
    Dim wrGETURL As System.Net.HttpWebRequest
    wrGETURL = DirectCast(System.Net.WebRequest.Create(sURL), HttpWebRequest)

    'Set our cookie container.
    wrGETURL.CookieContainer = Cookies

    ...your code...

End Function

您需要为每个具有相同会话的请求使用相同的CookieContainer，因此在发出所有请求之前在您的代码中声明一个：

Dim Cookies As New System.Net.CookieContainer

MakeRequest1(Cookies) 'Example request.
MakeRequest2(Cookies) 'Example request.

'Make the email request, passing our cookie container to it.
Dim Email As String = getemailaddress(Cookies)