Example of repo with "open" IQueryable

Program.cs

using Example;
using Microsoft.EntityFrameworkCore;

var repo = new ThingRepo();
repo.Init();

var cyanShapes = repo.GetThings(
    q => q.Where(
        q => q.Name.Contains(nameof(ConsoleColor.Cyan)))
    .OrderByDescending(s => s.Size));

foreach(var shape in cyanShapes)
{
    Console.WriteLine($"{shape.Name} ({shape.Size})");
}

namespace Example
{
    public class ThingRepo
    {
        public void Init()
        {
            var random = new Random();
            
            var colors = Enum.GetNames<ConsoleColor>();
            var shapes = new[] { "Square", "Circle", "Triangle", "Rectangle" };
            
            using var ctx = new ThingContext();
            
            foreach (var color in colors)
            {
                foreach (var shape in shapes)
                {
                    var thing = new Thing { Name = $"{color} {shape}", Size = random.Next(1, 200) };
                    ctx.Things.Add(thing);
                }
            }

            ctx.SaveChanges();
        }

        public IList<Thing> GetThings(Func<IQueryable<Thing>, IQueryable<Thing>> query)
        {
            using var ctx = new ThingContext();
            var queryToUse = query(ctx.Things);
            return queryToUse.ToList();
        }
    }
    public class Thing
    {
        public Guid Id { get; set; } = Guid.NewGuid();
        public string Name { get; set; } = string.Empty;
        public int Size { get; set; }
    }

    public class ThingContext : DbContext
    {
        public DbSet<Thing> Things { get; set; } = null!;
        protected override void OnConfiguring(DbContextOptionsBuilder optionsBuilder)
        {
            optionsBuilder.UseInMemoryDatabase("ThingDb");
            base.OnConfiguring(optionsBuilder);
        }
    }
}

QueryableRepoExample.csproj

<Project Sdk="Microsoft.NET.Sdk">

  <PropertyGroup>
    <OutputType>Exe</OutputType>
    <TargetFramework>net6.0</TargetFramework>
    <ImplicitUsings>enable</ImplicitUsings>
    <Nullable>enable</Nullable>
  </PropertyGroup>

  <ItemGroup>
    <PackageReference Include="Microsoft.EntityFrameworkCore.InMemory" Version="6.0.6" />
  </ItemGroup>

</Project>