// Entity Framework Classic

// Doc: https://entityframework-classic.net/csharp-eval-expression

​

// @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': 'Where',

      'Field': 'Name',

      'Operation': '==',

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

    },

    {

      'Method': 'Where',

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

    }

]

";

        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 == "Where") 

                {

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

                    {

                        query = query.Where(x => "x." + qc.Expression);

                    }

                    else

                    {

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

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

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

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

                        query = query.Where(x => expression);

                    }

                }

            }

            FiddleHelper.WriteTable(GetTitle(query.Expression), query.ToList());

        }

    }

​

    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 static string GetTitle(Expression expression)

    {

        return expression.ToString().Substring(expression.ToString().IndexOf(".Where"));

    }

​

    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; }

    }

}