The Standard is your friend, see [stmt.ranged]/1 For a range-based for statement of the form for ( for-range-declaration : expression ) statement let range-init be equivalent to the expression surrounded by parentheses ( expression ) and for a range-based for statement of the form for ( for-range-declaration : braced-init-list ) statement let range-init be equivalent … Read more
The best solution is usually to use the RemoveAll() method: myList.RemoveAll(x => x.SomeProp == “SomeValue”); Or, if you need certain elements removed: MyListType[] elems = new[] { elem1, elem2 }; myList.RemoveAll(x => elems.Contains(x)); This assume that your loop is solely intended for removal purposes, of course. If you do need to additional processing, then the … Read more
I keep this extension method around for this: public static void Each<T>(this IEnumerable<T> ie, Action<T, int> action) { var i = 0; foreach (var e in ie) action(e, i++); } And use it like so: var strings = new List<string>(); strings.Each((str, n) => { // hooray }); Or to allow for break-like behaviour: public static … Read more
Replace if (“state_$name” -eq “True”) { with: if ((Get-Variable -ValueOnly “state_$name”) -eq “True”) { That is, if your variable name is only known indirectly, via an expandable string, you cannot reference it directly (as you normally would with the $ sigil) – you need to obtain its value via Get-Variable, as shown above. However, as … Read more
If you iterate by reference, always unset the iteration variable afterwards: foreach ($objects as &$object) { // some code } unset($object); Excerpt from the foreach documentation: Reference of a $value and the last array element remain even after the foreach loop. It is recommended to destroy it by unset(). If you want to understand why … Read more
You can do something like this: int i = 0; foreach (var grouping in Class.Students.GroupBy(s => ++i / 20)) Console.WriteLine(“You belong to Group ” + grouping.Key.ToString());
Since the highest scoring answer states that the second method is better in every way, I feel compelled to post an answer here. True, looping by reference is more performant, but it isn’t without risks/pitfalls. Bottom line, as always: “Which is better X or Y”, the only real answers you can get are: It depends … Read more
Updated based on feedback from @BenAston & @trincot Roughly, this is what’s happening in both cases: For loop Set the index variable to its initial value Check whether or not to exit the loop Run the body of your loop Increment the index variable Back to step 2 The only overhead that happens on every … Read more
Yes, foreach will call Dispose() on the enumerator if it implements IDisposable.
Write the clearest code you can, and then benchmark and profile to discover any performance problems. If you do have performance problems, you can experiment with different code to work out whether it’s faster or not (measuring all the time with as realistic data as possible) and then make a judgement call as to whether … Read more