LINQ - Selecting from a data source with filter in C#
Example: 
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text.RegularExpressions;

namespace ForgetCode
{   
    public class MainClass
    {
        public static void Main()
        {
            // Load your DB file here
            var customerQuery =
            from cust in customers
            where cust.City == "London"
            select cust;
            
        }
    }
}