Notification does not contain a definition FCM in Xamarin - xamarin.forms

Question

I am having problem sending notification to specific devices with FCM.
This is how I get the specific device ID
Add Class in Android Project: FirebaseMessagingServiceDelegate.cs
[Service]
[IntentFilter(new[] { "com.google.firebase.MESSAGING_EVENT" })]
public class FirebaseMessagingServiceDelegate : FirebaseMessagingService
{
public async override void OnNewToken(string p0)
{
base.OnNewToken(p0);
var instanceIdResult = await FirebaseInstanceId.Instance.GetInstanceId().AsAsync<IInstanceIdResult>();
var token = instanceIdResult.Token;//(Token Devices)
}
}
Each time the user opens the App: var token = instanceIdResult.Token; will be changed. So every time I have to update the token on my server? Does this mean I also create a Class on Project iOS?
And this is how I send notifications to specific device:
PageOne.xaml.cs
protected void SendNotify()
{
// This registration token comes from the client FCM SDKs.
var registrationToken = "Token Devices";
// See documentation on defining a message payload.
var message = new Message()
{
Token = registrationToken,
Notification = new Notification()
{
Title = "Test from code",
Body = "Here is your test!"
}
};
// Send a message to the device corresponding to the provided
// registration token.
string response = FirebaseMessaging.DefaultInstance.SendAsync(message).Result;
// Response is a message ID string.
Console.WriteLine("Successfully sent message: " + response);
}
I received the error: Notification does not contain a definition for "Body"
I searched and found this article: firebase send notification from server c#. However I want to send directly from Xamarin App.
Hoping for any help. Thank you!