Top-level statements for EFGetStarted (#3865)

Migrate EFGetStarted sample to using top-level statements feature. (https://docs.microsoft.com/en-us/dotnet/csharp/fundamentals/program-structure/top-level-statements)

samples/core/GetStarted/Model.cs

@@ -1,8 +1,6 @@
-using System;
+using Microsoft.EntityFrameworkCore;
+using System;
 using System.Collections.Generic;
-using Microsoft.EntityFrameworkCore;
-
-namespace EFGetStarted;
 
 public class BloggingContext : DbContext
 {

samples/core/GetStarted/Program.cs

@@ -1,38 +1,30 @@
 using System;
 using System.Linq;
 
-namespace EFGetStarted;
+using var db = new BloggingContext();
 
-internal class Program
-{
-    private static void Main()
-    {
-        using var db = new BloggingContext();
+// Note: This sample requires the database to be created before running.
+Console.WriteLine($"Database path: {db.DbPath}.");
 
-        // Note: This sample requires the database to be created before running.
-        Console.WriteLine($"Database path: {db.DbPath}.");
+// Create
+Console.WriteLine("Inserting a new blog");
+db.Add(new Blog { Url = "http://blogs.msdn.com/adonet" });
+db.SaveChanges();
 
-        // Create
-        Console.WriteLine("Inserting a new blog");
-        db.Add(new Blog { Url = "http://blogs.msdn.com/adonet" });
-        db.SaveChanges();
+// Read
+Console.WriteLine("Querying for a blog");
+var blog = db.Blogs
+    .OrderBy(b => b.BlogId)
+    .First();
 
-        // Read
-        Console.WriteLine("Querying for a blog");
-        var blog = db.Blogs
-            .OrderBy(b => b.BlogId)
-            .First();
+// Update
+Console.WriteLine("Updating the blog and adding a post");
+blog.Url = "https://devblogs.microsoft.com/dotnet";
+blog.Posts.Add(
+    new Post { Title = "Hello World", Content = "I wrote an app using EF Core!" });
+db.SaveChanges();
 
-        // Update
-        Console.WriteLine("Updating the blog and adding a post");
-        blog.Url = "https://devblogs.microsoft.com/dotnet";
-        blog.Posts.Add(
-            new Post { Title = "Hello World", Content = "I wrote an app using EF Core!" });
-        db.SaveChanges();
-
-        // Delete
-        Console.WriteLine("Delete the blog");
-        db.Remove(blog);
-        db.SaveChanges();
-    }
-}
+// Delete
+Console.WriteLine("Delete the blog");
+db.Remove(blog);
+db.SaveChanges();