Program.cs File - Calling SnapshotAsync on Collection Reference

Program.cs

using CommandLine;
using Google.Cloud.Firestore;
using System;
using System.Collections.Generic;
using System.Threading.Tasks;

namespace GoogleCloudSamples
{
    public class QuickStartFirestoreProgram
    {
        public static string Usage = @"Usage:
C:\> dotnet run command project
C:\> dotnet run command my-project-id

Where command is one of
    retrieve-all-documents
";

        private static async void RetrieveAllDocuments(string project)
        {
            FirestoreDb db = FirestoreDb.Create(project);
            CollectionReference usersRef = db.Collection("users");
            QuerySnapshot snapshot = await usersRef.SnapshotAsync();
            foreach (DocumentSnapshot document in snapshot.Documents)
            {
                // Do anything you'd normally do with a DocumentSnapshot
                Dictionary<string, object> documentDictionary = document.ToDictionary();
                var firstName = documentDictionary["first"];
                Console.WriteLine("First name is {0}", firstName);
            }
        }

        public static void Main(string[] args)
        {
            if (args.Length < 2)
            {
                Console.Write(Usage);
                return;
            }
            string command = args[0].ToLower();
            string project = string.Join(" ",
                new ArraySegment<string>(args, 1, args.Length - 1));
            switch (command)
            {
                case "retrieve-all-documents":
                    RetrieveAllDocuments(project);
                    break;

                default:
                    Console.Write(Usage);
                    return;
            }
        }
    }
}