如何在xamarin for android中启用或发送whatsapp消息

using Android.Content;
using Android.Net;
using Android.OS;
using Android.Widget;
using Java.Lang;

public class MainActivity : Activity
{
    protected override void OnCreate(Bundle savedInstanceState)
    {
        base.OnCreate(savedInstanceState);
        SetContentView(Resource.Layout.Main);

        Button sendButton = FindViewById<Button>(Resource.Id.sendButton);
        EditText phoneNumberEditText = FindViewById<EditText>(Resource.Id.phoneNumberEditText);
        EditText messageEditText = FindViewById<EditText>(Resource.Id.messageEditText);

        sendButton.Click += (sender, e) =>
        {
            string phoneNumber = phoneNumberEditText.Text;
            string message = messageEditText.Text;

            SendWhatsAppMessage(phoneNumber, message);
        };
    }

    private void SendWhatsAppMessage(string phoneNumber, string message)
    {
        try
        {
            var uri = Uri.Parse("smsto:" + phoneNumber);
            var intent = new Intent(Intent.ActionSendTo, uri);
            intent.SetPackage("com.whatsapp");
            intent.PutExtra(Intent.Extra_TEXT, message);

            if (intent.ResolveActivity(PackageManager) != null)
            {
                StartActivity(intent);
            }
            else
            {
                Toast.MakeText(this, "WhatsApp not installed", ToastLength.Long).Show();
            }
        }
        catch (Exception ex)
        {
            Toast.MakeText(this, "Error: " + ex.Message, ToastLength.Long).Show();
        }
    }
}