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I'm trying to find the LINQ equivalent of the following code:
NameValueCollection nvc = new NameValueCollection(); List<BusinessLogic.Donation> donations = new List<BusinessLogic.Donation>(); donations.Add(new BusinessLogic.Donation(0, "", "", ""); donations.Add(new BusinessLogic.Donation(0, "", "", ""); donations.Add(new BusinessLogic.Donation(0, "", "", ""); for(var i = 0; i < donations.Count(); i++) { // NOTE: item_number_ + i - I need to be able to do this nvc.Add("item_number_" + i, donations[i].AccountName); } I was hoping I could use something like:
NameValueCollection nvc = new NameValueCollection(); List<BusinessLogic.Donation> donations = new List<BusinessLogic.Donation>(); donations.Add(new BusinessLogic.Donation(0, "", "", ""); donations.Add(new BusinessLogic.Donation(0, "", "", ""); donations.Add(new BusinessLogic.Donation(0, "", "", ""); donations.ForEach(x => nvc.Add("item_name_" + ??, x.AccountName); But I've not found a way to determine which iteration the loop is on. Any help would be appreciated!
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Luckily, there are several ways to get an index variable with foreach : Declare an integer variable before the loop, and then increase that one inside the loop with each loop cycle. Create a tuple that returns both the element's value and its index. Or swap the foreach loop with the for loop.
With the later C# versions so you also use tuples, so you'll have something like this: foreach (var (item, i) in Model. Select((v, i) => (v, i))) Allows you to access the item and index (i) directly inside the for-loop with tuple deconstruction.
forEach statement is a C# generic statement which you can use to iterate over elements of a List.
The following example uses type inference when deconstructing the list of 2-tuples returned by the Select() method. Now we can directly access the index and the value fields inside the loop. That's all about finding the current index in a foreach loop in C#.
LINQ doesn't have a ForEach method, and for good reason. LINQ is for performing queries. It is designed to get information from some data source. It is not designed to mutate data sources. LINQ queries shouldn't cause side effects, which is exactly what you're doing here.
The List class does have a ForEach method, which is what you are using. Because it's not actually in the System.Linq namespace it's not technically a part of LINQ.
There is nothing wrong with the for loop in your question. It would be wrong (from a good practice perspective) to try to change it in the way that you're trying to.
Here is a link that discusses the matter in more detail.
Now, if you want to ignore that advice and use a ForEach method anyway, it's not hard to write one that provides an index to the action:
public static void ForEach<T>(this IEnumerable<T> sequence, Action<int, T> action) { // argument null checking omitted int i = 0; foreach (T item in sequence) { action(i, item); i++; } } If you love us? You can donate to us via Paypal or buy me a coffee so we can maintain and grow! Thank you!
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