如何从具有线程的函数中获取返回值？

Question

我有这个功能

Public Function GetPage(ByVal dlURL As String) As String
    Dim S As String = ""
    Dim Request As HttpWebRequest = WebRequest.Create(dlURL)
    Dim Response As HttpWebResponse = Request.GetResponse()
    Using Reader As StreamReader = New StreamReader(Response.GetResponseStream())
        S = Reader.ReadToEnd()
    End Using
    Return S
End Function

它可以独立运作。但是，我正在尝试像这样

Dim threadRes
Dim dlThread = New Thread(Sub() threadRes = GetPage("http://www.dubstaphone.com/hub/betaversion.txt"))
dlThread.Start()

而threadRes是一个空白变量。我做错了什么？

编辑：当我执行GetPage（字符串）而不是线程的一部分时，该函数可以自行运行。