Updated readme and added new sample project

samples/ReadmeSample/Program.cs

@@ -0,0 +1,49 @@
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using Microsoft.EntityFrameworkCore;
+using ReadmeSample.Entities;
+using ReadmeSample.Extensions;
+
+namespace ReadmeSample
+{
+    class Program
+    {
+        static void Main(string[] args)
+        {
+            using var dbContext = new ApplicationDbContext();
+
+            // recreate database
+            dbContext.Database.EnsureDeleted();
+            dbContext.Database.EnsureCreated();
+
+            // Populate with seed data
+            var sampleUser = new User { UserName = "Jon", EmailAddress = "jon@doe.com" };
+            var sampleProduct = new Product { Name = "Blue Pen", ListPrice = 1.5m };
+            var sampleOrder = new Order {
+                User = sampleUser,
+                TaxRate = .19m,
+                CreatedDate = DateTime.UtcNow,
+                Items = new List<OrderItem> {
+                    new OrderItem { Product = sampleProduct, Quantity = 5  }
+                }
+            };
+
+            dbContext.AddRange(sampleUser, sampleProduct, sampleOrder);
+            dbContext.SaveChanges();
+
+            // Lets try a query!
+            var query = dbContext.Users
+                .Where(x => x.UserName == "Jon")
+                .Select(x => new {
+                    x.GetMostRecentOrderForUser(DateTime.UtcNow.AddDays(-30)).GrandTotal
+                });
+
+            var result = query.First();
+
+            Console.WriteLine($"Jons latest order had a grant total of {result.GrandTotal}");
+            Console.WriteLine($"The following query was used to fetch the results:");
+            Console.WriteLine(query.ToQueryString());
+        }
+    }
+}