Lambda Expression using Foreach Clause
.net-3.5, c#, foreach, lambda
Solution
It's perfectly possible to write a `ForEach` extension method for `IEnumerable<T>`.
I'm not really sure why it isn't included as a built-in extension method:
- Maybe because `ForEach` already existed on `List<T>` and `Array` prior to LINQ.
- Maybe because it's easy enough to use a `foreach` loop to iterate the sequence.
- Maybe because it wasn't felt to be functional/LINQy enough.
- Maybe because it isn't chainable. (It's easy enough to make a chainable version that `yield`s each item after performing an action, but that behaviour isn't particularly intuitive.)
public static void ForEach<T>(this IEnumerable<T> source, Action<T> action)
{
if (source == null) throw new ArgumentNullException("source");
if (action == null) throw new ArgumentNullException("action");
foreach (T item in source)
{
action(item);
}
}
Problem
Possible Duplicate: Why is there not a ForEach extension method on the IEnumerable interface? EDIT For reference, here's the blog post which eric referred to in the comments https://ericlippert.com/2009/05/18/foreach-vs-foreach/ ORIG More of a curiosity I suppose but one for the C# Specification Savants... Why is it that the ForEach() clause doesn't work (or isn't available) for use on IQueryable/IEnumerable result sets... You have to first convert your results ToList() or ToArray() Presumably theres a technical limitation to the way C# iterates IEnumerables Vs. Lists... Is it something to do with the Deferred Execution's of IEnumerables/IQuerable Collections. e.g. ``` var userAgentStrings = uasdc.UserAgentStrings .Where<UserAgentString>(p => p.DeviceID == 0 && !p.UserAgentString1.Contains("msie")); //WORKS userAgentStrings.ToList().ForEach(uas => ProcessUserAgentString(uas)); //WORKS Array.ForEach(userAgentStrings.ToArray(), uas => ProcessUserAgentString(uas)); //Doesn't WORK userAgentStrings.ForEach(uas => ProcessUserAgentString(uas)); ```