我如何通过post方法从vb.net发送多个变量到php

我找到了一个如何发送一个帖子到php的代码，但我只能发送一个变量。下面是我的代码:

Private Sub Button1_Click_1(sender As Object, e As EventArgs) Handles Button1.Click
    Dim postData = "msg=" & TextBox2.Text
    Dim request As WebRequest = WebRequest.Create("http://localhost/msg.php")
    request.Method = "POST"
    Dim byteArray As Byte() = Encoding.UTF8.GetBytes(postData)
    request.ContentType = "application/x-www-form-urlencoded"
    request.ContentLength = byteArray.Length
    Dim dataStream As Stream = request.GetRequestStream()
    dataStream.Write(byteArray, 0, byteArray.Length)
    dataStream.Close()
End Sub