using System;

using System.Collections.Generic;

using System.Globalization;

using System.Linq;

using System.Linq.Expressions;

using System.Reflection;

using System.Threading;

namespace ExpressionTreesExample

{

class Program

{

static void Main()

{

var cities = new List<City>(Enumerable.Range(0, 30).Select(x => new City { ru_Name = $"ru{x}", en_Name = $"en{x * 2}" }))

.AsQueryable();

var exprVisitor = new ExprVisitor();

var filter = "1";

Thread.CurrentThread.CurrentUICulture = CultureInfo.GetCultureInfo("ru");

var query = cities

.Where(x => x.Name.Contains(filter))

.Visit(exprVisitor); // changing query here

foreach (var city in query)

Console.WriteLine(city.Name);

Console.ReadLine();

}

}

public class City

{

[ExpressionLocalizable]

public string Name

{

get

{

switch (Thread.CurrentThread.CurrentUICulture.TwoLetterISOLanguageName)

{

case "ru":

return ru_Name;

case "en":

return en_Name;

default:

throw new NotSupportedException("Language is not supported");

}

}

set

{

switch (Thread.CurrentThread.CurrentUICulture.TwoLetterISOLanguageName)

{

case "ru":

ru_Name = value;

break;

case "en":

en_Name = value;

break;

default:

throw new NotSupportedException("Language is not supported");

}

}

}

public string ru_Name { get; set; }

public string en_Name { get; set; }

}

[AttributeUsage(AttributeTargets.Property)]

public class ExpressionLocalizableAttribute : Attribute { }

public class ExprVisitor : ExpressionVisitor

{

protected override Expression VisitMember(MemberExpression node)

{

if (node.Member.GetCustomAttribute<ExpressionLocalizableAttribute>() == null)

return base.VisitMember(node);

var nodeType = node.Expression.Type;

var localizedPropertyName = $"{Thread.CurrentThread.CurrentUICulture.TwoLetterISOLanguageName}_{node.Member.Name}";

var property = nodeType.GetProperty(localizedPropertyName);

if (property == null)

{

throw new NotSupportedException($"No such property '{localizedPropertyName}' in type '{nodeType.Name}'!");

}

return Expression.MakeMemberAccess(node.Expression, property);

}

}

public static class QueryExtensions

{

public static IQueryable<TResult> Visit<TResult>(this IQueryable<TResult> query, ExpressionVisitor visitor)

{

var expr = visitor.Visit(query.Expression);

return query.Provider.CreateQuery<TResult>(expr);

}

}

}