How do you get the index of the current iteration of a foreach loop?

Question

Is there some rare language construct I haven\'t encountered (like the few I\'ve learned recently, some on Stack Overflow) in C# to get a value representing the current iter

Answer 1

Ian Mercer posted a similar solution as this on Phil Haack's blog:

foreach (var item in Model.Select((value, i) => new { i, value }))
{
    var value = item.value;
    var index = item.i;
}

This gets you the item (item.value) and its index (item.i) by using this overload of LINQ's Select:

the second parameter of the function [inside Select] represents the index of the source element.

The new { i, value } is creating a new anonymous object.

Heap allocations can be avoided by using ValueTuple if you're using C# 7.0 or later:

foreach (var item in Model.Select((value, i) => ( value, i )))
{
    var value = item.value;
    var index = item.i;
}

You can also eliminate the item. by using automatic destructuring:

foreach ((MyType value, Int32 i) in Model.Select((value, i) => ( value, i )))
{
    
@value
}