This can get really cool with an extension (functioning as a proxy), for example:
collection.SelectWithIndex();
// vs.
collection.Select((item, index) => item);
Which will automagically assign indexes to the collection accessible via this Index property.
Interface:
public interface IIndexable
{
int Index { get; set; }
}
Custom extension (probably most useful for working with EF and DbContext):
public static class EnumerableXtensions
{
public static IEnumerable<TModel> SelectWithIndex<TModel>(
this IEnumerable<TModel> collection) where TModel : class, IIndexable
{
return collection.Select((item, index) =>
{
item.Index = index;
return item;
});
}
}
public class SomeModelDTO : IIndexable
{
public Guid Id { get; set; }
public string Name { get; set; }
public decimal Price { get; set; }
public int Index { get; set; }
}
// In a method
var items = from a in db.SomeTable
where a.Id == someValue
select new SomeModelDTO
{
Id = a.Id,
Name = a.Name,
Price = a.Price
};
return items.SelectWithIndex()
.OrderBy(m => m.Name)
.Skip(pageStart)
.Take(pageSize)
.ToList();