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CSharp · Console

/Program.cs

using System;
using System.Collections.Generic;
using System.Linq;
					
public class Program
{
	public static void Main()
    {
        // No need for Queryables. They're already dictionaries
        var englishResources = GetAllResourceValues(1);
        var arabicResources = GetAllResourceValues(2);
    
        // Start with all the english words. 
		// Use dictionary because it has efficient key matching.
        var merged = englishResources.ToDictionary( 
            i => i.Key, 
            i => new LanguageResourceModel { 
                    Name = i.Key, 
                    EnglishValue = i.Value.Value 
                });
        
        // Now merge the arabic ones. 
        // You could LINQ-ify the whole thing, but it's not gonna make it more efficient.
        LanguageResourceModel found;
        foreach (var item in arabicResources)
        {
            // If value already exists, update it
            if (merged.TryGetValue(item.Key, out found))
                found.ArabicValue = item.Value.Value;
            else // Otherwise, add a new one
                merged[item.Key] = new LanguageResourceModel { 
                    Name = item.Key, 
                    ArabicValue = item.Value.Value 
                };
        }
		
		//debug print
		merged.Values.ToList().ForEach(i => Console.WriteLine($"{i.Name}, English={i.EnglishValue}, Arabic={i.ArabicValue}"));
    }
    
    // Produce some values for testing
    public static Dictionary<string, KeyValuePair<int,string>> GetAllResourceValues(int languageId){
        if (languageId == 1) //english
            return new Dictionary<string, KeyValuePair<int, string>> {
                {"one", new KeyValuePair<int,string>(1, "one") },
                {"two", new KeyValuePair<int,string>(1, "two") },
                {"three", new KeyValuePair<int,string>(1, "three") },
            };
        else //spanish, cause I don't know arabic
            return new Dictionary<string, KeyValuePair<int, string>> {
                {"one", new KeyValuePair<int,string>(1, "uno") },
                {"four", new KeyValuePair<int,string>(1, "quatro") },
            };
    }
    
    // and simple class because I'm lazy
    public class LanguageResourceModel{ public string Name, EnglishValue, ArabicValue; }
}