如何读取从HttpWebRequest发送的POST数据

Question

Dim request As WebRequest = WebRequest.Create("http://www.example.com/a.aspx ")
request.Method = "POST"

Dim postData = Encoding.UTF8.GetBytes("example")
request.ContentLength = postData.Length
Dim dataStream As Stream = request.GetRequestStream()
dataStream.Write(postData, 0, postData.Length)
dataStream.Close()

随处可见上述示例，但另一方面-如何检索和处理请求数据（即"example"）？