using System;

using System.Collections.Generic;

using System.Linq;

using System.Linq.Expressions;

​

public static class DynWhere

{

    public static Expression<Func<T, bool>> CreatePredicate<T>(List<string> propsToSearch, string valueToSearch)

    {

        var parameter = Expression.Parameter(typeof(T), "record");

​

        // filtering is not required

        if (!propsToSearch.Any() || string.IsNullOrEmpty(valueToSearch))

            return Expression.Lambda<Func<T, bool>>(Expression.Constant(true), parameter);

​

        var props = typeof(T).GetProperties()

            .Select(p => p.Name)

            .Intersect(propsToSearch.Distinct());

​

        var containsMethod = typeof(string).GetMethod("Contains");

​

        var body = props

            .Select(p => Expression.PropertyOrField(parameter, p))

            .Aggregate((Expression)Expression.Constant(false),

                (c, n) => Expression.OrElse(c,

                    Expression.Call(n, containsMethod, Expression.Constant(valueToSearch)))

            );

​

        var lambda = Expression.Lambda<Func<T, bool>>(body, parameter);

        return lambda;

    }

​

    internal class MyDBObject

    {

        public MyDBObject()

        {

            // for demo, in real sql should work fine

            Prop1 = Prop2 = Prop3 = Prop4 = Prop5 =

            Prop11 = Prop12 = Prop13 = Prop14 = Prop15 =

            Prop21 = Prop22 = Prop23 = Prop24 = Prop25 =

            string.Empty;

        }

​

        public int Id { get; set; }

        public string Prop1 { get; set; }

        public string Prop2 { get; set; }

        public string Prop3 { get; set; }

        public string Prop4 { get; set; }

        public string Prop5 { get; set; }

        public string Prop11 { get; set; }

        public string Prop12 { get; set; }

        public string Prop13 { get; set; }

        public string Prop14 { get; set; }

        public string Prop15 { get; set; }

        public string Prop21 { get; set; }

        public string Prop22 { get; set; }

        public string Prop23 { get; set; }

        public string Prop24 { get; set; }

        public string Prop25 { get; set; }

    }

​

    public static void Main()

    {

        List<MyDBObject> dbRecords = new List<MyDBObject>

        {

            new MyDBObject { Id = 1, Prop2 = "O1_P2", Prop3 = "O1_P3", Prop12 = "O1_P12", Prop15 = "O1_P15", Prop24 = "O1_P24", Prop25 = "O1_P25" },

            new MyDBObject { Id = 2, Prop15 = "O2_P15", Prop21 = "test", Prop22 = "O2_P22", Prop23 = "O2_P23", Prop24 = "O2_P24", Prop25 = "O2_P25" },

            new MyDBObject { Id = 3, Prop21 = "O3_P21", Prop22 = "O3_P22", Prop23 = "O3_P23", Prop24 = "test", Prop25 = "O3_P25" }

        };

​

        var lambda = CreatePredicate<MyDBObject>(new[] { "Prop21", "Prop5" }.ToList(), "test");

​

        var query = dbRecords.AsQueryable().Where(lambda).ToArray();

​

        foreach (var rs in query)

        {

            Console.WriteLine("Id: " + rs.Id);

        }

    }

}