using System;
using System.Linq;
using System.Text.Json;

//first method
string[] names = { "Anna", "Pavel", "Ivan" };
var shortNames = names.Where(s => s.Length < 5);
//shortNames is {"Anna", "Ivan"}

//second method
var vNames = from name in names
             where name.Contains("v")
             select name;
//vNames is {"Pavel", "Ivan"}

Console.WriteLine(JsonSerializer.Serialize(shortNames));
Console.WriteLine(JsonSerializer.Serialize(vNames));