使用 ASP.net 向外部网站传递参数答案

【问题标题】：Using ASP.net to pass parameters to external website使用 ASP.net 向外部网站传递参数
【发布时间】：2013-03-26 09:25:22
【问题描述】：

我正在尝试访问需要登录网站并传递参数列表的页面。我似乎能够登录该站点（如果我更改登录详细信息，我会收到 401 未经授权的错误），但随后会收到 400 错误请求错误。代码有点散列在一起，所以我知道出了点问题，但不知道在哪里。

编辑代码

        Public Sub TestConn()


    Dim customeremailaddress As String = HttpUtility.UrlEncode("r.test@test.com")
    Dim customername As String = HttpUtility.UrlEncode("Ryan")
    Dim referenceid As String = HttpUtility.UrlEncode("ordertest123")
    Dim languagecode As String = HttpUtility.UrlEncode("1043")
    Dim expirydays As String = HttpUtility.UrlEncode("30")

    Dim UserName As String = "testusername"
    Dim password As String = "testpassword"
    Dim siteCredentials As New NetworkCredential(UserName, password)

    Dim URLAuth As String = "http://service.someurl.com/process.xml"
    Dim postString As String = String.Format("customeremailaddress={0}&customername={1}&referenceid={2}&languagecode={3}&expirydays={4}", customeremailaddress, customername, referenceid, languagecode, expirydays)

    Dim postBytes As Byte() = Encoding.UTF8.GetBytes(postString)

    Const contentType As String = "application/x-www-form-urlencoded"
    System.Net.ServicePointManager.Expect100Continue = False

    Dim cookies As New CookieContainer()
    Dim webRequest__1 As HttpWebRequest = TryCast(WebRequest.Create(URLAuth), HttpWebRequest)
    webRequest__1.Method = "POST"
    webRequest__1.ContentType = contentType
    webRequest__1.CookieContainer = cookies
    webRequest__1.ContentLength = postBytes.Length
    webRequest__1.UserAgent = "Mozilla/5.0 (Windows; U; Windows NT 5.1; en-US; rv:1.9.0.1) Gecko/2008070208 Firefox/3.0.1"
    webRequest__1.Accept = "text/html,application/xhtml+xml,application/xml;q=0.9,*/*;q=0.8"
    webRequest__1.Referer = "http://service.someurl.com/process.xml"
    webRequest__1.Credentials = siteCredentials

    Try
        Dim requestStream As Stream = webRequest__1.GetRequestStream()
        requestStream.Write(postBytes, 0, postBytes.Length)
        Dim responseReader As New StreamReader(webRequest__1.GetResponse().GetResponseStream())
        Dim responseData As String = responseReader.ReadToEnd()
        responseReader.Close()
        webRequest__1.GetResponse().Close()

    Catch ex As Exception
        Lbl_ConnTest_error.Text = ex.Message
    End Try

End Sub

【问题讨论】：

首先使用 Fiddler2 fiddler2.com/fiddler2 查看请求/响应详细信息，看看是否指向正确的方向。
还可以查看这个示例msdn.microsoft.com/en-gb/library/debx8sh9.aspx - 它可能更容易阅读 - 而且它的 POSTing 数据不要忘记正确格式化 postData 即 url 编码值部分并创建键值对，即 variable1= Some%20value&variable2=Another%20Value
我认为这可能是我收到错误请求的地方，因为我不知道实际传递参数列表的语法是什么。我猜到了 - Dim postString As String = String.Format("customeremailaddress={0}&customername={1}&referenceid={2}&languagecode={3}&expirydays={4}", customeremailaddress, customername, referenceid, languagecode, expirydays ) - 但我确定这看起来不对？
您需要将 @Sani 的答案与围绕您的值包装 HttpServerUtility.UrlEncode() 结合起来，即 Dim customeremailaddress As String = HttpServerUtility.UrlEncode("r.test@test.com")
您现在正在写入字节两次。这就是内容长度不匹配的原因。您不需要StreamWriter。删除与 requestWriter 对象有关的所有代码。正如 bUKaneer 所说，您还需要 UrlEncode 查询字符串中的值。

标签： asp.net vb.net web-services

【解决方案1】：

您需要发送postString 的字节而不是字符串本身：

Dim postBytes As Byte() = Encoding.UTF8.GetBytes(postString)
...
webRequest__1.ContentLength = postBytes.Length
...
Dim requestStream As Stream = webRequest__1.GetRequestStream()
requestStream.Write(postBytes, 0, postBytes.Length)

更多信息here。

【讨论】：

我已经进行了这些更改，但现在在线收到 (400) Bad Request - Dim responseReader As New StreamReader(webRequest__1.GetResponse().GetResponseStream()) - 接近尾声。
我已经稍微整理了代码，现在得到：要写入流的字节超过指定的 Content-Length 字节大小。与 UTF8 编码有关吗？
检查您在设置ContentLength 时指定的是postBytes.Length 而不是postString.Length。还要检查当您 Write 到流时，您指定了 postBytes.Length 属性。
已使用内容长度字节问题的完整代码编辑了原始帖子。