Apply function to all elements of collection through LINQ

Question

I have recently started off with LINQ and its amazing  I was wondering if LINQ would allow me to apply a function - any function - to all the elements of a collection  without using foreach  Something like python lambda functions   For example if I have a int list  Can I add a constant to every element using LINQ  If i have a DB table  can i set a field for all records using LINQ   I am using C

User · Answer

You can try something like   var foo    from fooItems in context footable select fooItems fooID   1     Returns a list of id s  1  you can do the same with using a function to whatever you have in the select clause   Update  As suggested from Jon Skeet this is a better version of the snippet of code I just posted   var foo   context footable Select foo   gt  foo fooID   1

User · Answer

I found some way to perform in on dictionary contain my custom class methods  foreach  var item in this Values Where p   gt  p IsActive    false               item Refresh      Where  this  derived from   Dictionary lt string  MyCustomClass gt   class MyCustomClass       public void Refresh

User · Answer

A common way to approach this is to add your own ForEach generic method on IEnumerable lt T gt   Here s the one we ve got in MoreLINQ   public static void ForEach lt T gt  this IEnumerable lt T gt  source  Action lt T gt  action        source ThrowIfNull  source        action ThrowIfNull  action        foreach  T element in source                action element              Where ThrowIfNull is an extension method on any reference type  which does the obvious thing    It ll be interesting to see if this is part of  NET 4 0  It goes against the functional style of LINQ  but there s no doubt that a lot of people find it useful   Once you ve got that  you can write things like   people Where person   gt  person Age  lt  21         ForEach person   gt  person EjectFromBar

User · Answer

The idiomatic way to do this with LINQ is to process the collection and return a new collection mapped in the fashion you want   For example  to add a constant to every element  you d want something like  var newNumbers   oldNumbers Select i   gt  i   8     Doing this in a functional way instead of mutating the state of your existing collection frequently helps you separate distinct operations in a way that s both easier to read and easier for the compiler to reason about   If you re in a situation where you actually want to apply an action to every element of a collection  an action with side effects that are unrelated to the actual contents of the collection  that s not really what LINQ is best suited for  although you could fake it with Select  or write your own IEnumerable extension method  as many people have    It s probably best to stick with a foreach loop in that case

User · Answer

For collections that do not support ForEach you can use static ForEach method in Parallel class   var options   new ParallelOptions     MaxDegreeOfParallelism   1    Parallel ForEach  your collection   options  x   gt  x  Your Method

User · Answer

haha  man  I just asked this question a few hours ago  kind of    try this   example   someIntList ForEach i  gt i 5     ForEach   is one of the built in  NET methods  This will modify the list  as opposed to returning a new one

User · Answer

Or you can hack it up    Items All p   gt    p IsAwesome   true  return true

User · Answer

You could also consider going parallel  especially if you don t care about the sequence and more about getting something done for each item   SomeIEnumerable lt T gt  AsParallel   ForAll  Action lt T gt    Delegate   Lambda     For example   var numbers   new     1  2  3  4  5    numbers AsParallel   ForAll  Console WriteLine      HTH

[c#] Apply function to all elements of collection through LINQ

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