C# How do I use a variable in a Linq select statement using Query Syntax

Question

I'm trying to get the name of item but I'm having to hard code the locale in the select statement. This is my code

private void GetOrder(Root Wix)
    {
        string locale = Wix.restaurant.locale;
        List<Item> menu = Wix.menu.items;
        List<OrderItem> orderItems = Wix.order.orderItems;
        foreach (var orderItem in orderItems)
        {
            string itemId = orderItem.itemId;
            string itemName = (from m in menu  where m.id==itemId select m.title.en_GB).FirstOrDefault();

            int count = orderItem.count;
            string comment = orderItem.comment;
            int price = orderItem.price;
        }

        string orderComment = Wix.order.comment;
        int totalPrice = Wix.order.price;
    }

How can I replace the hard coded "en_GB" in select m.title.en_GB to the locale value returned in the string locale = Wix.restaurant.locale ?

Please provide source code of Item class and classes used in it. — Alexey Rumyantsev
– Alexey Rumyantsev, Commented Feb 19, 2021 at 12:58
And you can also remove linq tag from question, it is not related to LINQ. — Alexey Rumyantsev
– Alexey Rumyantsev, Commented Feb 19, 2021 at 13:31

SomeBody · Accepted Answer · 2021-02-19 15:08:02Z

3

You can use reflection:

string itemName = (from m in menu  where m.id==itemId select (string)m.title.GetType().GetProperty(locale).GetValue(m.title)).FirstOrDefault();

This will throw an exception if the class of your title object has no property that has the same name as the content of the string locale. The following variant will make your itemName null if no such property exists:

string itemName = (from m in menu  where m.id==itemId select (string)m.title.GetType().GetProperty(locale)?.GetValue(m.title)).FirstOrDefault();

edited Feb 19, 2021 at 15:08

answered Feb 19, 2021 at 13:05

SomeBody

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2 Comments

Paul Clark Over a year ago

Sorry, I'm getting an error; "Object does not match target type." when I use either of the 2 statements above

SomeBody Over a year ago

Sorry, that was a typo. I already updated the answer.

Alexey Rumyantsev · Accepted Answer · 2021-02-19 13:24:11Z

3

Instead of using slow reflection based approach you can introduce interface like this

public interface ILocalizableString
{
    string en_GB { get; }

    string ru_RU { get; }

    //and so on
}

Implement it by your localized strings and introduce extension method

public static class LocalizableStringExtensions
{
    public static string GetString(this ILocalizableString str, string locale)
    {
        if(str == null)
            return null;
        if(locale == "en_GB")
            return str.en_GB;
        if(locale == "ru_RU")
            return str.ru_RU;
        return str.en_GB; //default
     }
  }

Then in your code

  string itemName = (from m in menu  where m.id==itemId select m.title.GetString(locale)).FirstOrDefault();

This can guarantee good performance, and simple way to extended list of supported languages.

answered Feb 19, 2021 at 13:24

Alexey Rumyantsev

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2 Comments

Gleb Over a year ago

I'd suggest using switch expression instead of if - else statements. ` return locale switch { "en_GB" => item.title.en_GB, "ru_RU" => item.title.ru_RU, ... _ => "undefined" }; `

Alexey Rumyantsev Over a year ago

I think switch expressions are too recent to use them in answers, many people can find them unfamiliar, or may be restricted in language version. If/return approach is clear and obvious, and those who want will convert it to switch or whatever they need.

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