#nullable disable

​

using System;

using System.Collections;

using System.Collections.Generic;

using System.Text.Json;

using System.Linq;

public class Program

{

    public static void Main()

    {

        List<SomeEntity> entities = [

            new SomeEntity("1111", "1111", "1111"),

            new SomeEntity("2222", "2222", "2222"),

            new SomeEntity("3333", "3333", "3333"),

            new SomeEntity("4444", "4444", "4444"),

            new SomeEntity("1111", "2222", "3333"),

            new SomeEntity("1111", "2222", "2222"),

            new SomeEntity("22122", "2222", "11211"),

        ];

        var someFilter = new SomeFilter("1", null, "2");

        var filtered = Filter(entities.AsQueryable(), someFilter);

        Console.WriteLine(JsonSerializer.Serialize(filtered, new JsonSerializerOptions { WriteIndented = true }));

        Console.WriteLine("");

        var filtered2 = Filter2(entities.AsQueryable(), someFilter);

        Console.WriteLine(JsonSerializer.Serialize(filtered, new JsonSerializerOptions { WriteIndented = true }));

    }

    public static IQueryable<SomeEntity> Filter(IQueryable<SomeEntity> entities, SomeFilter filter)

    {

        if (filter.Property1 is not null)

            entities = entities.Where(o => o.Property1.Contains(filter.Property1));

        if (filter.Property2 is not null)

            entities = entities.Where(o => o.Property2.Contains(filter.Property2));

        if (filter.Property3 is not null)

            entities = entities.Where(o => o.Property3.Contains(filter.Property3));

        return entities;

    }

    public static IQueryable<SomeEntity> Filter2(IQueryable<SomeEntity> entities, SomeFilter filter)

    {

        switch (true)

        {

            case true when filter.Property1 is not null:

                entities = entities.Where(o => o.Property1.Contains(filter.Property1));

                break;

            case true when filter.Property2 is not null:

                entities = entities.Where(o => o.Property2.Contains(filter.Property2));

                break;

            case true when filter.Property3 is not null:

                entities = entities.Where(o => o.Property3.Contains(filter.Property3));

                break;

            default:

                break;

        }

        return entities;

    }

}

​

public record SomeFilter(string Property1, string Property2, string Property3);

public record SomeEntity(string Property1, string Property2, string Property3);