Today our customer report a good point to improve the performance in our product. It is about the loop in .NET. In the test, they found the for loop is has better performance than foreach.
I know this one for a long time. But when I verified it, I found another case, the loop doesn't affect the performance too much, but really affected by the type of list you are using. See the result below.
Loop with List
Loop with Array
Loop with ArrayList
Loop with Collection
If I didn't do this test, I cannot tell which is better. I used to use Collection<T> a lot; but next time, I guess I need to be more careful to use the list type from now on. The result is: Use Array > List<T> > ArrayList > Collection<T>.
PS. this source code can be compiled by .NET 3.5 Client profiler ~ .NET 4.5.2. So some statement is not fashion.