gistfile1.cs

dotnet new tool-manifest
dotnet tool install dotnet-ef

dotnet ef

dotnet add App/App.csproj package Microsoft.EntityFrameworkCore.Design
dotnet add App/App.csproj package Microsoft.EntityFrameworkCore.Tools
dotnet add App/App.csproj package Microsoft.EntityFrameworkCore.SQLite

dotnet ef migrations add "initial"
dotnet ef migrations list
dotnet ef database update

-----

using System;
using System.Collections.Generic;
using System.Linq;
using Microsoft.EntityFrameworkCore;

namespace App
{
    public class DataContext : DbContext
    {
        public DbSet<Dog> Dogs { get; set; }
        public DbSet<Owner> Owners { get; set; }

        protected override void OnConfiguring(DbContextOptionsBuilder options)
            => options.UseSqlite("Data Source=app.db");

        protected override void OnModelCreating(ModelBuilder modelBuilder)
        {
            var dogs = new Dog[] {
                new Dog { Id = 1, Name = "Lassy"},
                new Dog { Id = 2, Name = "Molly"},
                new Dog { Id = 3, Name = "Frank"},
            };

            modelBuilder.Entity<Dog>().HasData(dogs);

            var owners = new Owner[] {
                new Owner { Id = 1, Name = "Don"},
                new Owner { Id = 2, Name = "Jackie"},
                new Owner { Id = 3, Name = "Sara"},
            };

            modelBuilder.Entity<Owner>().HasData(owners);

            base.OnModelCreating(modelBuilder);
        }
    }
}

using System;
using System.Collections.Generic;
using System.Linq;
using Microsoft.EntityFrameworkCore;

namespace App
{
    class Program
    {
        static void Main(string[] args)
        {
            var database = new DataContext();

            Console.WriteLine("#1");
            Console.WriteLine("Basic query");
            var dogs = database.Dogs.ToList();
            foreach(var dog in dogs)
            {
                Console.WriteLine($"{dog.Id} : {dog.Name}");
            }

            Console.WriteLine("#2");
            Console.WriteLine("Using OrderBy");
            database.Dogs.OrderByDescending(d => d.Name).ToList().ForEach(dog => Console.WriteLine(dog.Name));

            Console.WriteLine("#3");
            Console.WriteLine("Using Where");
            database.Dogs.Where(d => d.Id > 1).OrderBy(d => d.Name).ToList().ForEach(dog => Console.WriteLine(dog.Name));

            Console.WriteLine("#4");
            Console.WriteLine("Inserting a record");
            var d1 = new Dog{Name="Zoro"};
            database.Add(d1);

            Console.WriteLine("#5");
            Console.WriteLine("Inserting multiple records");
            var puppies = new List<Dog>{new Dog{Name="Frodo"}, new Dog{Name="Gandalf"}};
            database.AddRange(puppies);
            database.SaveChanges();

            Console.WriteLine("#6");
            Console.WriteLine("Associating records");
            var owner = database.Owners.Where(o => o.Name == "Sara").First();
            database.Dogs.Where(d => d.Id > 3).ToList().ForEach(d => d.Owner = owner);
            database.SaveChanges();

            Console.WriteLine("#7");
            Console.WriteLine("Querying a relationship");
            var sara = database.Owners.Where(o => o.Name == "Sara").First();
            Console.WriteLine($"Owner: {sara.Name}");
            sara.Pets.ToList().ForEach(p => Console.WriteLine($"Pet: {p.Name}"));
        }
    }
}


using System;
using System.Collections.Generic;
using System.Linq;
using Microsoft.EntityFrameworkCore;

namespace App
{
    class Program
    {
        static void Main(string[] args)
        {
            var database = new DataContext();

            Console.WriteLine("#1");
            Console.WriteLine("Basic query");
            var dogs = database.Dogs.ToList();
            foreach(var dog in dogs)
            {
                Console.WriteLine($"{dog.Id} : {dog.Name}");
            }

            Console.WriteLine("#2");
            Console.WriteLine("Using OrderBy");
            database.Dogs.OrderByDescending(d => d.Name).ToList().ForEach(dog => Console.WriteLine(dog.Name));

            Console.WriteLine("#3");
            Console.WriteLine("Using Where");
            database.Dogs.Where(d => d.Id > 1).OrderBy(d => d.Name).ToList().ForEach(dog => Console.WriteLine(dog.Name));

            Console.WriteLine("#4");
            Console.WriteLine("Inserting a record");
            var d1 = new Dog{Name="Zoro", Age=21};
            database.Add(d1);

            Console.WriteLine("#5");
            Console.WriteLine("Inserting multiple records");
            var puppies = new List<Dog>{new Dog{Name="Frodo", Age=23}, new Dog{Name="Gandalf", Age=25}};
            database.AddRange(puppies);
            database.SaveChanges();

            Console.WriteLine("#6");
            Console.WriteLine("Associating records");
            var owner = database.Owners.Where(o => o.Name == "Sara").First();
            database.Dogs.Where(d => d.Id > 3).ToList().ForEach(d => d.Owner = owner);
            database.SaveChanges();

            Console.WriteLine("#7");
            Console.WriteLine("Querying a relationship");
            var sara = database.Owners.Where(o => o.Name == "Sara").First();
            Console.WriteLine($"Owner: {sara.Name}");
            sara.Pets.ToList().ForEach(p => Console.WriteLine($"Pet: {p.Name}"));

            // ----------------------------------
            // using LINQ instead of method calls
            // ----------------------------------

            Console.WriteLine("\nBasic query");
            var dogs1 = from dog in database.Dogs
                       select dog;

            dogs1.ToList().ForEach(dog => Console.WriteLine(dog.Name));


            Console.WriteLine("\nGet dogs by name in descending order");
            dogs1 = from dog in database.Dogs
                    orderby dog.Name descending
                    select dog;

            dogs1.ToList().ForEach(dog => Console.WriteLine(dog.Name));


            Console.WriteLine("\nGet names of dogs in ascending order");
            var names = from dog in database.Dogs
                        orderby dog.Name ascending
                        select dog.Name;

            names.ToList().ForEach(name => Console.WriteLine(name));


            Console.WriteLine("\nCreate anonymous object from query");
            var objects1 = from dog in database.Dogs
                           select new {Name=dog.Name, Owner=dog.Owner.Name ?? "Anonymous"};

            objects1.ToList().ForEach(obj => Console.WriteLine($"{obj.Owner} is the owner of {obj.Name}"));


            Console.WriteLine("\nUsing where");
            var objects2 = from dog in database.Dogs
                           where dog.Age > 4
                           select new {Name=dog.Name, Age=dog.Age};

            objects2.ToList().ForEach(obj => Console.WriteLine($"{obj.Name} is {obj.Age} years old"));


            Console.WriteLine("\nGet the first result from a query");
            var object3 = (from dog in database.Dogs
                           select new {Name=dog.Name, Age=dog.Age}).First();

            Console.WriteLine($"The first dog is {object3.Name} and is {object3.Age} years old");


            Console.WriteLine("\nGet the count of dogs");
            var count = (from dog in database.Dogs
                         select new {Name=dog.Name, Age=dog.Age}).Count();

            Console.WriteLine($"There are {count} dogs in the database");


            Console.WriteLine("\nUsing quantifiers");
            var owners1 = from o in database.Owners
                          where o.Pets.Any(pet => pet.Age > 20)
                          select o;

            owners1.ToList().ForEach(owner => Console.WriteLine($"{owner.Name} has at least one dog over the age of 20"));
        }
    }
}