// Entity Framework Classic

// Doc: https://entityframework-classic.net/linq-dynamic

​

// @nuget: Z.EntityFramework.Classic

// @nuget: Newtonsoft.Json

​

using System;

using System.Collections.Generic;

using System.Data.Entity;

using System.Linq;

using System.Linq.Expressions;  

using Newtonsoft.Json;

using Z.Expressions;

​

public class Program

{

    public static void Main()

    {

        GenerateData();

        var json = @"

[

    {

      'Method': 'LongCount',

      'Field': 'Name',

      'Operation': '==',

      'Value': '""Customer_A""',

    },

    {

      'Method': 'LongCount',

      'Expression': 'Description.Contains(""ZZZ Projects"")',

    } ,

    {

      'Method': 'LongCount',

      'Expression': 'Description.Contains(""Fiddle"")',

    } 

]

";

        var queryCriterias = JsonConvert.DeserializeObject<List<Criteria>>(json);

​

        using (var context = new EntityContext())

        {       

            var query = context.Customers.AsQueryable();

            foreach(var qc in queryCriterias)

            {

                if(qc.Method == "LongCount") 

                {

                    if(!string.IsNullOrEmpty(qc.Expression))

                    {

                        var count = query.LongCount(x => "x." + qc.Expression);

                        Console.WriteLine("Expression : x." + qc.Expression + "\nLongCount Result : " + count );

                    }

                    else

                    {

                        var expression = "x.[Field] [Operation] [Value]"

                        .Replace("[Field]", qc.Field)

                        .Replace("[Operation]", qc.Operation)

                        .Replace("[Value]", qc.Value);

                        var count = query.LongCount(x => expression);

                        Console.WriteLine("Expression : " + expression + "\nLongCount Result : " + count );

                    }

                    Console.WriteLine("\n");

                }

            }

        }

    }

​

    public static void GenerateData()

    {

        using (var context = new EntityContext())

        {

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

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

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

            context.SaveChanges();  

        }

    }

​

    public class EntityContext : DbContext

    {       

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

        {       

        }

​

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

    }

    public class Customer

    {

        public int CustomerID { get; set; }

        public string Name { get; set; }

        public string Description { get; set; }

    }

    public class Criteria

    {

        public string Method { get; set; }

        public string Field { get; set; }

        public string Operation { get; set; }

        public string Value { get; set; }

        public string Expression { get; set; }

    }

}