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CSharp · Console

/Program.cs

using System;
using System.Linq;
					
public class Program
{
	public static void Main()
	{
		Console.WriteLine("Hello World");
		var items = new InternalConditionModel[]
		{
			new InternalConditionModel { ProductId = "a", IsSSoldOnlyOnDisplay = false, Value = 1},
			new InternalConditionModel { ProductId = "a", IsSSoldOnlyOnDisplay = true, Value = 2}, // should be chosen
			new InternalConditionModel { ProductId = "b", IsSSoldOnlyOnDisplay = true, Value = 2},
			new InternalConditionModel { ProductId = "b", IsSSoldOnlyOnDisplay = true, Value = 4}, // should be chosen
			new InternalConditionModel { ProductId = "b", IsSSoldOnlyOnDisplay = true, Value = 3}, 
		};
		var result = items.GroupBy(x => x.ProductId).Select(x => x.OrderByDescending(y => y.Value).FirstOrDefault(y => x.Count(z => z.IsSSoldOnlyOnDisplay) == 1 ? y.IsSSoldOnlyOnDisplay : true));
		foreach(var item in result)
		{
			Console.WriteLine("id="+item.ProductId+", Value="+item.Value);
		}
	}
}

class InternalConditionModel
{
    public string ProductId { get; set; }
    public double Value { get; set; }
    public DateTime DateFrom { get; set; }
    public DateTime DateThru { get; set; }
    public bool IsSSoldOnlyOnDisplay { get; set; }
}