Linq style For Each

Question

Is there any Linq style syntax for  For each  operations   For instance  add values based on one collection to another  already existing one   IEnumerable lt int gt  someValues   new List lt int gt      1  2  3     IList lt int gt  list   new List lt int gt      someValues ForEach x   gt  list Add x   1      Instead of   foreach int value in someValues      list Add value   1

User · Answer

There isn t anything built-in  but you can easily create your own extension method to do it   public static void ForEach lt T gt  this IEnumerable lt T gt  source  Action lt T gt  action        if  source    null  throw new ArgumentNullException  source        if  action    null  throw new ArgumentNullException  action         foreach  T item in source                action item

User · Answer

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 lt T gt  this IEnumerable lt T gt   this  Action lt T gt  action       foreach  var x in  this        action x

User · Answer

Using the ToList   extension method is your best option   someValues ToList   ForEach x   gt  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   gt  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

User · Answer

The Array and List lt T gt  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 lt T gt  objects   public static void ForEach lt T gt  this IEnumerable lt T gt  source  Action lt T gt  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

User · Answer

There isn t anything like that in standard Linq  but there is a ForEach operator in MoreLinq

User · Answer

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   gt  x 1     or if you really need it in a List   var someValues   new List lt int gt   list Select  x   gt  x 1

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