可以参考这个示例代码来使用HttpWebRequest类：
' 创建一个HttpWebRequest对象 Dim request As HttpWebRequest = DirectCast(WebRequest.Create(url), HttpWebRequest)
' 设置请求头 request.Method = "POST" request.ContentType = "application/x-www-form-urlencoded"
' 发送POST请求 Dim postData As String = "username=test&password=123" Dim dataBytes As Byte() = Encoding.UTF8.GetBytes(postData) request.ContentLength = dataBytes.Length Using requestStream As Stream = request.GetRequestStream() requestStream.Write(dataBytes, 0, dataBytes.Length) requestStream.Close() End Using
' 获取响应 Dim response As HttpWebResponse = DirectCast(request.GetResponse(), HttpWebResponse) Dim responseStream As Stream = response.GetResponseStream() Dim reader As New StreamReader(responseStream) Dim responseText As String = reader.ReadToEnd()
' 关闭响应流 reader.Close() responseStream.Close() response.Close()
其中，url是请求的地址，postData是POST请求的参数。在此示例中，我们设置了POST请求的Content-Type为application/x-www-form-urlencoded，可以根据实际需要进行修改。在使用GetRequestStream()方法获取请求流之后，我们将POST请求的参数转换成字节数组，并写入请求流中。最后，使用GetResponse()方法获取响应，并关闭相关的流。