DaftarActivity.cs

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using Android.App;
using Android.Content;
using Android.OS;
using Android.Runtime;
using Android.Views;
using Android.Widget;
using Newtonsoft.Json.Linq;
using System.Net;
using System.Collections.Specialized;
using Android.Util;

namespace PariwisataJateng
{
    [Activity(Label = "Register", Theme = "@style/Temaku")]
    public class DaftarActivity : Activity
    {
        protected override void OnCreate(Bundle bundle)
        {
            base.OnCreate(bundle);
            SetContentView(Resource.Layout.Daftar);
            // untuk komponen
            EditText nama = FindViewById<EditText>(Resource.Id.txtNama);
            EditText email = FindViewById<EditText>(Resource.Id.txtEmail);
            EditText password = FindViewById<EditText>(Resource.Id.txtPassword);
            EditText no_telp = FindViewById<EditText>(Resource.Id.txtTelp);
            Button simpan = FindViewById<Button>(Resource.Id.btnSimpan);
            Button batal = FindViewById<Button>(Resource.Id.btnBatal);

            batal.Click += delegate {
                StartActivity(typeof(LoginActivity));
            };


            simpan.Click += delegate
            {
                //buat variabel terlebih dahulu
                string xnama = nama.Text;
                string xemail = email.Text;
                string xpassword = password.Text;
                string xtelp = no_telp.Text;
                string xlevel ="3";

                // mengecek semua komponen sudah diisi atau tidak
                if (xnama == "")
                {
                    Toast.MakeText(this, "Masukan nama anda !", ToastLength.Short).Show();
                    nama.RequestFocus();
                    return;
                }
                else if (!isValidEmail(xemail))
                {
                    Toast.MakeText(this, "Email tidak valid ! ", ToastLength.Short).Show();

                }
                else if (xpassword == "")
                {
                    Toast.MakeText(this, "Masukan Password !", ToastLength.Short).Show();
                    password.RequestFocus();
                    return;
                }
                else if (xtelp == "")
                {
                    Toast.MakeText(this, "Masukan No Handphone !", ToastLength.Short).Show();
                    no_telp.RequestFocus();
                    return;
                }
                else
                {
                    //buat tampungnya dalam array

                    var data = new NameValueCollection();
                    data["nama"] = xnama;
                    data["email"] = xemail;
                    data["password"] = xpassword;
                    data["no_telp"] = xtelp;
                    data["id_level"] = xlevel;

                    WebClient client = new WebClient();
                    client.Encoding = Encoding.UTF8;
                    var reply = client.UploadValues
                    ("https://banyu.center/pariwisatajateng/api/pendaftaran?", "POST", data);
                    //usr.Text = reply.ToString();

                    //membuat kondisi
                    //set alert for executing the task
                    AlertDialog.Builder alert = new AlertDialog.Builder(this);
                    alert.SetTitle("Confirmasi");
                    alert.SetMessage("Apakah anda yakin akan menyimpan data ini ?");
                    alert.SetPositiveButton("Yes", (senderAlert, args) =>
                    {
                        Toast.MakeText(this, "Input Data Berhasil!", ToastLength.Short).Show();
                        //jika berhasil maka hapus isi komponennya
                        nama.Text = "";
                        email.Text = "";
                        password.Text = "";
                        no_telp.Text = "";
                        StartActivity(typeof(LoginActivity));
                    });

                    alert.SetNegativeButton("Cancel", (senderAlert, args) =>
                    {
                        Toast.MakeText(this, "Pendaftaran digagalkan!", ToastLength.Short).Show();
                    });

                    Dialog dialog = alert.Create();
                    dialog.Show();
                }
            };
        }
        public bool isValidEmail(string email)
        {
            return Android.Util.Patterns.EmailAddress.Matcher(email).Matches();
        }
    }
}