Here I am a going to explains how to send mobile notifications from Firebase using ASP.NET CORE 3.0 with Firebase Admin SDK.

Follow the steps:

Step 1: Add the FirebaseAdmin package by NuGet.

Step 2: Get a Firebase service account key from Project Setting -> Service account -> Click on generate new private key.

Step 3:  Initialize the FirebaseAdmin SDK from Startup.cs

public IServiceProvider ConfigureServices(IServiceCollection services)  
var googleCredential = _hostingEnvironment.ContentRootPath;  
 var filePath = Configuration.GetSection("GoogleFirebase")["fileName"];  
 googleCredential = Path.Combine(googleCredential, filePath);  
 var credential = GoogleCredential.FromFile(googleCredential);  
 FirebaseApp.Create(new AppOptions()  
 {  
   
 Credential = credential  
 });  
}  

4. Define Method for Sending Notification

public virtual async Task<string> SendNotification(List<string> clientToken, string title, string body)  
 {  
 var registrationTokens = clientToken;  
 var message = new MulticastMessage()  
 {  
 Tokens = registrationTokens,  
 Data = new Dictionary<string, string>()  
 {  
 {"title", title},  
 {"body", body},  
 },  
 };  
 var response = await FirebaseMessaging.DefaultInstance.SendMulticastAsync(message).ConfigureAwait(true);  
 return "";  
 }