How to send notification Google FCM through ASP.NET VB

Dim response As String
        Dim serverKey As String = "fcm server key"
        Dim senderId As String = "sender id"
       Dim deviceId As String = "api token"

        Dim tRequest As WebRequest = WebRequest.Create("https://fcm.googleapis.com/fcm/send")
        tRequest.Method = "post"
        tRequest.ContentType = "application/json"

        Dim data = New With {
            .[to] = deviceId,
            .notification = New With {
                .body = "test meassage",
                .title = "Welcome",
                .sound = "Enabled"
            }
        }

        Dim serializer As New JavaScriptSerializer()
        Dim json = serializer.Serialize(data)
        Dim byteArray As Byte() = Encoding.UTF8.GetBytes(json)
        tRequest.Headers.Add(String.Format("Authorization: key={0}", serverKey))
        tRequest.Headers.Add(String.Format("Sender: id={0}", senderId))
        tRequest.ContentLength = byteArray.Length

        Using dataStream As Stream = tRequest.GetRequestStream()
            dataStream.Write(byteArray, 0, byteArray.Length)

            Using tResponse As WebResponse = tRequest.GetResponse()

                Using dataStreamResponse As Stream = tResponse.GetResponseStream()

                    Using tReader As StreamReader = New StreamReader(dataStreamResponse)
                        Dim sResponseFromServer As String = tReader.ReadToEnd()
                        response = sResponseFromServer
                    End Using
                End Using
            End Using
        End Using