Re: Optimal use of foreach

When you use foreach, it actually calls myDictionary.Keys.GetEnumerator()
which returns a new instance of IEnumerator<T>. That enumerator is then used
during the loop and Keys is never called again. Open up Reflector and take a
look at the code, you will better understand what's going on this way ;)

for loops are usually used in inner loops where you don't want to create
millions of new IEnumerator<T>. They are also slightly faster on arrays, but
the vast majority of the time, foreach is fine and makes the code clearer.

Sébastien
On Tue, Jan 27, 2009 at 8:43 PM, Mont Rothstein <[email protected]>wrote:

> When using foreach if the collection is a property will it be called on
> each
> pass or only once?
>
> Can I do:
>
> foreach (string key in myDictionary.Keys)
> {
> }
>
> or will that call Keys each time, therefore requiring that I do:
>
> Dictionary<string, string>.KeysCollections keys;
>
> keys = myDictionary.Keys;
>
> foreach (string key in keys)
> {
> }
>
> Thanks,
> -Mont
>
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