push notification to android using c#

Question

The below code i found in some websites but it always return error

multicast_id":6719893729607364541,"success":0,"failure":1,"canonical_ids":0,"results":[{"error":"InvalidRegistration"}]}

Code is:

WebRequest tRequest = WebRequest.Create("https://fcm.googleapis.com/fcm/send");

tRequest.Method = "post";

//serverKey - Key from Firebase cloud messaging server

tRequest.Headers.Add(string.Format("Authorization: key={0}", "Server key"));

//Sender Id - From firebase project setting

tRequest.Headers.Add(string.Format("Sender: id={0}", "Sender Id"));

tRequest.ContentType = "application/json";

var payload = new

{

to = "//topics//news", // even "/topics/news:

priority = "high",

content_available = true,

notification = new

{

body = "Test",

title = "Test",

badge = 1

},

data = new

{

key1 = "value1",

key2 = "value2"

}

};

string postbody = JsonConvert.SerializeObject(payload).ToString();

Byte[] byteArray = Encoding.UTF8.GetBytes(postbody);

tRequest.ContentLength = byteArray.Length;

using (Stream dataStream = tRequest.GetRequestStream())

{

dataStream.Write(byteArray, 0, byteArray.Length);

using (WebResponse tResponse = tRequest.GetResponse())

{

using (Stream dataStreamResponse = tResponse.GetResponseStream())

{

if (dataStreamResponse != null) using (StreamReader tReader = new StreamReader(dataStreamResponse))

{

String sResponseFromServer = tReader.ReadToEnd();

//result.Response = sResponseFromServer;

this.Label.Text = sResponseFromServer;

}

}

}

}