Linq style "For Each"
Solution 1
Using the ToList() extension method is your best option:
someValues.ToList().ForEach(x => list.Add(x + 1));
There is no extension method in the BCL that implements ForEach directly.
Although there's no extension method in the BCL that does this, there is still an option in the System
namespace... if you add Reactive Extensions to your project:
using System.Reactive.Linq;
someValues.ToObservable().Subscribe(x => list.Add(x + 1));
This has the same end result as the above use of ToList
, but is (in theory) more efficient, because it streams the values directly to the delegate.
Solution 2
The Array
and List<T>
classes already have ForEach
methods, though only this specific implementation. (Note that the former is static
, by the way).
Not sure it really offers a great advantage over a foreach
statement, but you could write an extension method to do the job for all IEnumerable<T>
objects.
public static void ForEach<T>(this IEnumerable<T> source, Action<T> action)
{
foreach (var item in source)
action(item);
}
This would allow the exact code you posted in your question to work just as you want.
Solution 3
There isn't anything built-in, but you can easily create your own extension method to do it:
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);
}
}
Solution 4
The official MS line is "because it's not a functional operation" (ie it's a stateful operation).
Couldn't you do something like:
list.Select( x => x+1 )
or if you really need it in a List:
var someValues = new List<int>( list.Select( x => x+1 ) );
Solution 5
There is no Linq ForEach extension. However, the List
class has a ForEach method on it, if you're willing to use the List
directly.
For what it's worth, the standard foreach
syntax will give you the results you want and it's probably easier to read:
foreach (var x in someValues)
{
list.Add(x + 1);
}
If you're adamant you want an Linq style extension. it's trivial to implement this yourself.
public static void ForEach<T>(this IEnumerable<T> @this, Action<T> action)
{
foreach (var x in @this)
action(x);
}
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Stefan Steinegger
I create software for a couple of years now. After 10+ years of coding in C# I'm now arrive on Java island. Seen a lot of weird stuff ...
Updated on January 31, 2020Comments
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Stefan Steinegger almost 4 years
Is there any Linq style syntax for "For each" operations?
For instance, add values based on one collection to another, already existing one:
IEnumerable<int> someValues = new List<int>() { 1, 2, 3 }; IList<int> list = new List<int>(); someValues.ForEach(x => list.Add(x + 1));
Instead of
foreach(int value in someValues) { list.Add(value + 1); }
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LukeH about 14 yearsSee also this blog post from Eric Lippert, regarding the rationale for not including
ForEach
in the BCL: blogs.msdn.com/ericlippert/archive/2009/05/18/…
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Noldorin about 14 yearsYou have a point about functional vs. stateful operations. However, F# was designed as a functional length, and has an equivalent
ForEach
method. -
Stefan Steinegger about 14 yearsThanks, It's clear that I could write the extension myself. I just want to use built in stuff as far as possible before doing this.
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Noldorin about 14 yearsYeah, that's fair enough. I also make sure I'm not reinventing BCL functionality too. In this case, there's none however.
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DLL_Whisperer over 7 yearsArray class doesn't have a ForEach method :) but there is a "EnumerableExtensions" statşc class in Microsoft.Practices.ObjectBuilder2 namespace. it has foreach method for IEnumerable :)
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user3431501 over 5 yearsCan you give a reference for "The official MS line"? I'm interested in reading the rest of their take.
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stusmith over 5 yearsI probably shouldn't have used the word "official", but this is the blog I was thinking of: blogs.msdn.microsoft.com/ericlippert/2009/05/18/…
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Dan Csharpster about 5 yearsWhy isn't there anything built in? Am I missing something? This seems like much needed basic functionality.
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Casey about 3 years@DanCsharpster because linq methods aren't supposed to have side effects