How to create custom Extension Method for CRUD operation in .NET core 3.1 (without LINQ) using EF Core?

Question

For example I want to perform a Select operation :

var payerData = this.context.Payers
                .Where(x => x.Id == Data.ID)
                .Select(x => new { 
                    x.someID,
                    x.Status
                });

Now I want to generalize this as an extension method so that it can be used with other tables also. Is it possible to do this? If yes, than how?

I tried to find the solution but everywhere it is given about LINQ and I want this in EF Core. And I am a beginner in .Net Core.

Answer 1

If you are asking how to reuse query for entities that share some of the properties, then you could:

1. Create interface and apply it to every entity.
2. Create extension method and pass interface type as generic limitation.

Small demo below. I am not sure how to help with part of your question about using LINQ since whole EF Core is built around it

using Microsoft.EntityFrameworkCore;
using System.Linq;

namespace ConsoleApp5
{
    public interface TypeWithFields
    {
        int Id { get; set; }
        int SomeId { get; set; }
        string Status { get; set; }
    }

    public class A : TypeWithFields
    {
        public int Id { get; set; }
        public int SomeId { get; set; }
        public string Status { get; set; }
    }

    public class B : TypeWithFields
    {
        public int Id { get; set; }
        public int SomeId { get; set; }
        public string Status { get; set; }
    }

    public class MyContext : DbContext
    {
        public MyContext(DbContextOptions options) : base(options)
        {
        }

        public DbSet<A> As { get; set; }

        public DbSet<B> Bs { get; set; }
    }

    public class QueryDto
    {
        public int Id { get; set; }
        public int SomeId { get; set; }
        public string Status { get; set; }
    }

    public static class DbContextExtensions
    {
        public static IQueryable<QueryDto> Filter<T>(this IQueryable<T> query, int id)
            where T: TypeWithFields
        {
            return query.Where(x => x.Id == id)
                .Select(x => new QueryDto
                {
                    Id = x.Id,
                    SomeId = x.SomeId,
                    Status = x.Status
                });
        }
    }

    class Program
    {
        static void Main(string[] args)
        {
            var builder = new DbContextOptionsBuilder().UseInMemoryDatabase("memorydb");
            var dbContext = new MyContext(builder.Options);

            var queryAs = dbContext.As.Filter(1).ToList();
            var queryBs = dbContext.Bs.Filter(1).ToList();
        }
    }
}