EfCoreExperiments.cs

using Microsoft.EntityFrameworkCore;
using Microsoft.Extensions.DependencyInjection;
using Xunit;

namespace EfCoreExperiments
{
    public class UnitTest1
    {
        [Fact]
        public void RequestDbContextFromServices()
        {
            var services = new ServiceCollection()
                .AddEntityFrameworkInMemoryDatabase()
                .AddDbContext<TestDbContext>(options => options.UseInMemoryDatabase("test database"))
                .BuildServiceProvider();

            // with two constructors available this uses the one that takes DbContextOptions
            var dbContext = services.GetRequiredService<TestDbContext>();
            Assert.NotNull(dbContext);
        }

        [Fact]
        public void RequestDbContextFactoryFromServices()
        {
            var services = new ServiceCollection()
                .AddEntityFrameworkInMemoryDatabase()
                .AddDbContextFactory<TestDbContext>(options => options.UseInMemoryDatabase("test database"))
                .BuildServiceProvider();

            // this throws System.InvalidOperationException, Multiple constructors accepting all given argument types have been found in type 'EfCoreExperiments.TestDbContext'. There should only be one applicable constructor.
            var factory = services.GetRequiredService<IDbContextFactory<TestDbContext>>();

            // code never gets this far
            var dbContext = factory.CreateDbContext();
            Assert.NotNull(dbContext);
        }
    }

    public class TestDbContext : DbContext
    {
        /// <summary>
        /// For use with EF core tooling
        /// </summary>
        public TestDbContext()
        {
        }

        /// <summary>
        /// For configuring via options
        /// </summary>
        /// <param name="options"></param>
        public TestDbContext(DbContextOptions<TestDbContext> options)
        {
        }
    }
}