How to continuously check internet connection in Xamarin Forms

Does your app need to constantly check it’s internet connectivity?
Do you want to inform your user that he/she is disconnected from the net?
In this post, we will create a quick wifi connection detector while the app is running.

Step 1: Add any connectivity images in your Android drawable directory and iOS Resources directory. Images should be both connected and disconnected images.

Step 2: Search xam.plugin.connectivity in the Manage NuGet Package Solution.

Step 3: Install the xam.plugin.connectivity NuGet package in all your projects.

 MainPage.xaml

<?xml version="1.0" encoding="utf-8" ?>
<ContentPage
    x:Class="CheckConn.MainPage"
    xmlns="http://xamarin.com/schemas/2014/forms"
    xmlns:x="http://schemas.microsoft.com/winfx/2009/xaml"
    xmlns:local="clr-namespace:CheckConn">
    <Grid>
        <Grid.RowDefinitions>
            <RowDefinition Height="100" />
        </Grid.RowDefinitions>
        <Grid.ColumnDefinitions>
            <ColumnDefinition Width="5*" />
            <ColumnDefinition Width="5*" />
        </Grid.ColumnDefinitions>


        <Image Grid.Column="0" Source="{Binding Conn}" />

        <Label
            Grid.Column="1"
            FontSize="Large"
            HorizontalOptions="Center"
            Text="{Binding x}"
            VerticalOptions="Center" />
    </Grid>
</ContentPage>

MainPage.xaml.cs file(Code behind)

using Xamarin.Forms;

namespace CheckConn
{
    public partial class MainPage : ContentPage
    {
        public MainPage()
        {
            InitializeComponent();
            BindingContext = new MainViewModel();
        }
    }
}

Now for View Model (MainViewModel.cs)

using CheckConn.Annotations;
using System.ComponentModel;
using System.Runtime.CompilerServices;
using Plugin.Connectivity;
using System;
using System.Net.Http;
using System.Threading.Tasks;
using Xamarin.Forms;

namespace CheckConn
{
    internal class MainViewModel : INotifyPropertyChanged
    {
        private string _conn;
        private string _x;
        public string Conn
        {
            get => _conn;
            set
            {
                _conn = value;
                OnPropertyChanged();
            }
        }

        public string x
        {
            get => _x;
            set
            {
                _x = value;
                OnPropertyChanged();
            }
        }
        public MainViewModel()
        {
            CheckWifiOnStart();
            CheckWifiContinuously();
        }

        public async void CheckWifiOnStart()
        {
            x = "0 kb/sec";
            Conn = CrossConnectivity.Current.IsConnected ? "online.png" : "offline.png";
            await StartTest();
        }

        public void CheckWifiContinuously()
        {
           Device.StartTimer(TimeSpan.FromSeconds(1), OnTimerTick);

            CrossConnectivity.Current.ConnectivityChanged += (sender, args) =>
            {
                x = "0 kb/sec";
                Conn = args.IsConnected ? "online.png" : "offline.png";
              

            };
        }
        bool  OnTimerTick()
        {
            Conn = CrossConnectivity.Current.IsConnected ? "online.png" : "offline.png";
            StartTest();
            return true;
        }
        public async Task StartTest()
        {
            try
            {
                //string url =
                //"http://puresourcecode.com/file.axd?file=/SpeedTest/1024kb.txt";

               string url =
              "https://www.google.com/";

               HttpClient client = new HttpClient();

                // get current tickcount
                double starttime = Environment.TickCount;

                // download file from the specified URL,
                // and save it to C:\speedtest.txt
                // in your project change the path of the following line
                var httpResponse = await client.GetAsync(url);
                byte[] dataBuffer =
                       await httpResponse.Content.ReadAsByteArrayAsync();

                // get current tickcount
                double endtime = Environment.TickCount;

                // how many seconds did it take?
                // we are calculating this by subtracting starttime from
                // endtime and dividing by 1000 (since the tickcount is in
                // miliseconds 1000 ms = 1 sec)
                double SecondsForOneMb = Math.Floor(endtime - starttime) / 1000;

                // calculate download rate in kb per sec.
                // this is done by dividing 1024 by the number of seconds it
                // took to download the file (1024 bytes = 1 kilobyte)
                double KbSeconds = Math.Round(1024 / SecondsForOneMb);
                x = KbSeconds.ToString() + "kb/sec";
            }
            catch(Exception ex)
            {
                x = "0 kb/sec";
            }
        }
        public event PropertyChangedEventHandler PropertyChanged;

        [NotifyPropertyChangedInvocator]
        protected virtual void OnPropertyChanged([CallerMemberName] string propertyName = null)
        {
            PropertyChanged?.Invoke(this, new PropertyChangedEventArgs(propertyName));
        }
    }
}

Full source code link : https://drive.google.com/open?id=1xH_GvTJpmPUgFez9G3xm8SP0QyfcjXfb