// Entity Framework Classic

// Doc: https://entityframework-classic.net/query-filter

​

// @nuget: Z.EntityFramework.Classic

​

using System;

using System.Linq;

using System.Data.Entity;

​

public class Program

{

    public static void Main()

    {

        GenerateData();

​

        using (var context = new EntityContext())

        {

            var filter = context.Configuration.QueryFilter.Filter<ISoftDelete>(QueryFilterType.SoftDelete.ToString(), customer => !customer.IsDeleted);

​

            // SELECT * FROM Customers WHERE IsDeleted = 0

            FiddleHelper.WriteTable("Customers", context.Customers.ToList());

            // Get the `QueryFilter` with the specified id.

            var queryFilter = context.Configuration.QueryFilter.GetFilter(QueryFilterType.SoftDelete.ToString());

            queryFilter.Disable();

            // SELECT * FROM Customers

            var list = context.Customers.ToList();          

            FiddleHelper.WriteTable("Customers", list);     

        }

    }

    public static void GenerateData()

    {

        using (var context = new EntityContext())

        {

            context.Customers.Add(new Customer() { Name = "Customer_A", Description = "Description" });

            context.Customers.Add(new Customer() { Name = "Customer_B", Description = "Description", IsDeleted = true });           

            context.Customers.Add(new Customer() { Name = "Customer_C", Description = "Description" });

            context.SaveChanges();  

        }

    }

​

    public class EntityContext : DbContext

    {

        public EntityContext() : base(FiddleHelper.GetConnectionStringSqlServer())

        {

        }

        public DbSet<Customer> Customers { get; set; }

    }

    public interface ISoftDelete

    {

        bool IsDeleted { get; set; }

    }

    public class Customer : ISoftDelete

    {

        public int CustomerID { get; set; }

        public string Name { get; set; }

        public string Description { get; set; }

        public bool IsDeleted { get; set; }

    }

    public enum QueryFilterType

    {

        SoftDelete,

        FilterX,

        FilterY,

        FilterZ

    }

}