在C＃4中将属性设置为null的最快方法

Question

What is the fastest way to set properties (any one) to null in an IEnumerable ? Is foreach my only option?

Answer 1

If you have a very large list, you could consider doing this in parallel:

enumerable.AsParallel().ForAll(a => a.Value = null);

But worth benchmarking and baring in mind that your objects will now need to be threadsafe.

Quick tests here showed a return on investment when the list size was above 10 million items*. Lower list sizes and the costs of setting up the parallel processing outweighs the benefits.

*Your Mileage Will Vary

Answer 2

There are two ways of achieving your goal:

1. As you mentioned:

    foreach(var item in enumeration) { item.Property = null; } 

2. You can go with LINQ also:

    enumeration.ToList().ForEach(item => item.Property = null); 

While the second way looks a shorter and better readable, it may execute slower, because as Jeppe Stig Nielsen pointed out, the IEnumerable gets converted into a List (be enumerating it the first time) and that list gets enumerated again, to finally set the property.

Thus you are right: foreach is your only option. However the foreach -representation will look like, you always will need to iterate over the collection to modify each item.