https://stackoverflow.com/questions/48459247/problemin-adding-index-field-to-linq-results

stack.48459247.cs

void Main()
{
	var data = new[]
	{
		new Asset{Id=1, Name="one"},
		new Asset{Id=2, Name="two"},
		new Asset{Id=3, Name="three"},
		new Asset{Id=4, Name="four"},
		new Asset{Id=5, Name="five"},
		new Asset{Id=6, Name="six"},
		new Asset{Id=7, Name="seven"},
		new Asset{Id=8, Name="eight"},
		new Asset{Id=9, Name="nine"},
		new Asset{Id=10, Name="ten"},
		new Asset{Id=11, Name="eleven"},
		new Asset{Id=12, Name="twelve"},
	};

	var paged = data.Page(page: 2, size: 5);
	paged.Dump();

	var indexed = paged.Items
		.Select((current, index) =>
		{
			var skipped = (paged.Page - 1) * paged.Size;
			return new
			{
				Index = skipped + index,
				Item = current,
			};
		});
	indexed.Dump();
}

public static class Extensions
{
	public static Paged<T> Page<T>(this IEnumerable<T> instance, int? page = 1, int? size = 10)
	{
		var items = instance
			.Skip((page.Value - 1) * size.Value)
			.Take(size.Value)
			.ToList();

		return new Paged<T>()
		{
			Page = page.Value,
			Size = size.Value,
			Total = instance.Count() - 1,
			Items = items,
		};
	}
}

public class Paged<T>
{
	public IEnumerable<T> Items { get; set; }
	public int Page { get; set; }
	public int Size { get; set; }
	public int Total { get; set; }
}

public class Asset
{
	public int Id { get; set; }
	public string Name { get; set; }
}