Call a method in the declaration of a foreach

Question

I have a foreach which calls a method to get its collection.

 foreach(var item in GetItemDetails(item))
 {
 }

Visual studio doesn't complain about this, nor does Resharper, however, before I continue to use this approach, I want to reach out and check if it is a recommended approach.

score 11 · Accepted Answer · answered Jan 29 '14 at 13:50

11

There's nothing wrong with that. The method will only be evaluated once.

It is basically:

using(var iter = GetItemDetails(item).GetEnumerator())
{
    while(iter.MoveNext()
    {
        var item = iter.Current;
        // ...
    }
}

answered Jan 29 '14 at 13:50

Marc Gravell

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score 1 · Answer 2 · edited May 23 '17 at 11:49

1

There's nothing wrong with it.

Just two suggestions:

If what you will put in the loop can written as a method for single items, which would make it re-usable, I would also consider the List.ForEach(...); method. Info: http://msdn.microsoft.com/en-us/library/bwabdf9z%28v=vs.110%29.aspx
In case you'd be really after performance (which may happen even in C#), the for loop is usually the fastest, though less readable as less concise code: Info: In .NET, which loop runs faster, 'for' or 'foreach'?

edited May 23 '17 at 11:49

Community

1
1

answered Jan 29 '14 at 14:03

TTT

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the times when `List.ForEach` would be preferable to regular `foreach` are *minute* - not least, keep in mind that `List` has a custom `struct` iterator, making it pretty damned efficient. And re `for` vs `foreach`, that is **hugely** dependent on the scenario, and usually makes very little difference. The difference in most *actual doing stuff* code is so small that you're essentially just profiling your profiler. – Marc Gravell Jan 29 '14 at 14:47
Thank you. Maybe it's because English is not my mother language, but there is something I'm not sure to get in your first sentence. I did not mention .ForEach() for performance reason, just for readability. If agree about the for loop, that why I mentionned "may happen even in C#", but I have already encountered specific cases in which this kind of optimization proved to be useful. – TTT Jan 29 '14 at 15:10

Call a method in the declaration of a foreach

2 Answers2