Let’s start.

Step 1 : Open Visual Studio->New Project->Templates->Visual C#->Android->Blank app.Then Give the Project Name and Project Location.

Step 2 : Go to Solution Explorer-> Project Name-> Components, right click to get more components. The new dialog box will open. This dialog box will be used to search the GCM. Add the Google Play Services-GCM Packages.

Add Namespace,

using Android.Gms.Common;

MainActivity.cs :

 protected override void OnCreate(Bundle bundle) 
 { 
 base.OnCreate(bundle); 
 // Set our view from the "main" layout resource 
 SetContentView(Resource.Layout.Main); 
 IsPlayServicesAvailable() 
 } 
 public bool IsPlayServicesAvailable() 
 { 
 int resultCode = GooglePlayServicesUtil.IsGooglePlayServicesAvailable(this); 
 if (resultCode != ConnectionResult.Success) 
 { 
 if (GooglePlayServicesUtil.IsUserRecoverableError(resultCode)) 
 txtmsg.Text = GooglePlayServicesUtil.GetErrorString(resultCode); 
 else 
 { 
 Toast.MakeText(this, "Sorry, this device is not supported", ToastLength.Short) 
 .Show(); 
 Finish(); 
 } 
 return false; 
 } 
 else 
 { 
 Toast.MakeText(this, "Google Play Services is available.", ToastLength.Short) 
 .Show(); 
 return true; 
 } 
 }

Step 4 : Register with GCM in Android Developer Console,

Go to https://console.developers.google.com, create New Project and give project Name. Refer to the screenshots, given below:

Next, enable API for Google Cloud Messaging.

Step 5 : Register with GCM in the application. Here, we need InstanceID. Hence, go to the developer console to get InstanceID. Find Project information and get the project number.

Step 6 : Next is Implementation Registration Intent Service in Android Application. Create a new class Registrationintentservice.cs and give the  code, shown below,

C# Code :

 [Service(Exported = false)] 
 class RegistrationIntentService: IntentService 
 { 
 static readonly string[] Topics = { 
 "global" 
 }; 
 public RegistrationIntentService(): base("RegistrationIntentService") 
 {} 
 protected override void OnHandleIntent(Intent intent) 
 { 
 try 
 { 
 Log.Info("RegistrationIntentService", "Calling InstanceID.GetToken"); 
 lock(this) 
 { 
 var instanceID = InstanceID.GetInstance(this); 
 var token = instanceID.GetToken( 
 "YOUR_INSTANCE_ID", GoogleCloudMessaging.InstanceIdScope, null); 
 Log.Info("RegistrationIntentService", "GCM Registration Token: " + token); 
 SendRegistrationToAppServer(token); 
 SubscribeToTopics(token, Topics); 
 } 
 } 
 catch (Exception e) 
 { 
 Log.Debug("RegistrationIntentService", "Failed to get a registration token"); 
 return; 
 } 
 } 
 void SendRegistrationToAppServer(string token) 
 { 
 // Add custom implementation here as needed. 
 } 
 void SubscribeToTopics(string token, string[] topics) 
 { 
 foreach(var topic in topics) 
 { 
 var pubSub = GcmPubSub.GetInstance(this); 
 pubSub.Subscribe(token, "/topics/" + topic, null); 
 } 
 } 
 }

Step 7 : Next, run Registrationintentservice.cs. Hence, again modify MainActivity.cs;  open Solution Explorer-> Project Name-> MainActivity.cs.

 protected override void OnCreate(Bundle bundle) 
 { 
 base.OnCreate(bundle); 
 // Set our view from the "main" layout resource 
 SetContentView(Resource.Layout.Main); 
 txtmsg = FindViewById < TextView > (Resource.Id.txtmsg); 
 btnsend = FindViewById < Button > (Resource.Id.btnsend); 
 if (IsPlayServicesAvailable()) 
 { 
 var intent = new Intent(this, typeof(RegistrationIntentService)); 
 StartService(intent); 
 } 
 }

Step 8 : Next is Implementation InstanceId Listener Service in Android Application. Create new class InstanceIdListenerService.cs and give the following code:

C# Code :

 [Service(Exported = false), IntentFilter(new [] 
 { 
 "com.google.android.gms.iid.InstanceID" 
 })] 
 class MyInstanceIDListenerService: InstanceIDListenerService 
 { 
 // When a token refresh happens, start my RegistrationIntentService: 
 public override void OnTokenRefresh() 
 { 
 var intent = new Intent(this, typeof(RegistrationIntentService)); 
 StartService(intent); 
 } 
 }

Step 9 : Next is Implementation GCM Listener Service in Android Application. Create new class GcmListenerService.cs and give the following code. This code receives the Notifications Title, Icon, and Message.

 [Service(Exported = false), IntentFilter(new [] 
 { 
 "com.google.android.c2dm.intent.RECEIVE" 
 })] 
 public class MyGcmListenerService: GcmListenerService 
 { 
 public override void OnMessageReceived(string from, Bundle data) 
 { 
 // Extract the message received from GCM: 
 var message = data.GetString("message"); 
 Log.Debug("MyGcmListenerService", "From: " + from); 
 Log.Debug("MyGcmListenerService", "Message: " + message); 
 // Forward the received message in a local notification: 
 SendNotification(message); 
 } 
 // Use Notification Builder to create and launch the notification: 
 void SendNotification(string message) 
 { 
 var intent = new Intent(this, typeof(MainActivity)); 
 intent.AddFlags(ActivityFlags.ClearTop); 
 var pendingIntent = PendingIntent.GetActivity(this, 0, intent, PendingIntentFlags.OneShot); 
 var notificationBuilder = new Notification.Builder(this) 
 .SetSmallIcon(Resource.Drawable.Icon) //Icon 
 .SetContentTitle("C#Corner") //Title 
 .SetContentText(message) //Message 
 .SetAutoCancel(true) 
 .SetContentIntent(pendingIntent); 
 var notificationManager = (NotificationManager) GetSystemService(Context.NotificationService); 
 notificationManager.Notify(0, notificationBuilder.Build()); 
 } 
 }

Step 10 : Go to Solution Explorer-> Project Name-> References and right click to Manage NuGet Packages, the new dialog box will open. This dialog box is used to search Json and install the Newtonsoft.Json Packages.

 using Newtonsoft.Json.Linq; 
 using System.Net.Http; 
 using System.Net.Http.Headers; 
 using System.Text; 
 using System.Threading.Tasks; 
 protected override void OnCreate(Bundle bundle) 
 { 
 base.OnCreate(bundle); 
 // Set our view from the "main" layout resource 
 SetContentView(Resource.Layout.Main); 
 btnsend.Click += (object sender, EventArgs e) => 
 { 
 OnButtonClicked(sender, e); 
 }; 
 } 
 public async void OnButtonClicked(object sender, EventArgs args) 
 { 
 var MESSAGE = txtmsg.Text; 
 var jGcmData = new JObject(); 
 var jData = new JObject(); 
 jData.Add("message", MESSAGE); 
 jGcmData.Add("to", "/topics/global"); 
 jGcmData.Add("data", jData); 
 string a; 
 var url = new Uri("https://gcm-http.googleapis.com/gcm/send"); 
 try 
 { 
 using(var client = new HttpClient()) 
 { 
 client.DefaultRequestHeaders.Accept.Add( 
 new MediaTypeWithQualityHeaderValue("application/json")); 
 client.DefaultRequestHeaders.TryAddWithoutValidation( 
 "Authorization", "key=" + API_KEY); 
 Task.WaitAll(client.PostAsync(url, new StringContent(jGcmData.ToString(), Encoding.Default, "application/json")) 
 .ContinueWith(response => 
 { 
 Console.WriteLine(response); 
 Console.WriteLine("Message sent: check the client device notification tray."); 
 })); 
 } 
 } 
 catch (Exception e) 
 { 
 Console.WriteLine("Unable to send GCM message:"); 
 Console.Error.WriteLine(e.StackTrace); 
 } 
 }

<receiver android:name="com.google.android.gms.gcm.GcmReceiver" android:exported="true" android:permission="com.google.android.c2dm.permission.SEND"> 
 <intent-filter> 
 <action android:name="com.google.android.c2dm.intent.RECEIVE" /> 
 <action android:name="com.google.android.c2dm.intent.REGISTRATION" /> 
 <category android:name="GCM.GCM" /> 
 </intent-filter> 
</receiver> 
</application> 
<uses-permission android:name="com.google.android.c2dm.permission.RECEIVE" /> 
<uses-permission android:name="android.permission.WAKE_LOCK" /> 
<uses-permission android:name="android.permission.INTERNET" /> 
<uses-permission android:name="GCM_ANDROID.GCM_ANDROID.permission.C2D_MESSAGE" />

Anbu Mani

Anbu Mani(Microsoft MVP) is working Software Engineer in Changepond Technologies, Chennai, Tamilnadu, India. Having 4+ years of experience and his area of interest is C#, ASP.NET, SQL Server, Xamarin and Xamarin Forms,Azure…etc

anbumani.dev/