Apply function to all elements of collection through LINQ [duplicate]

Answer 1

haha, man, I just asked this question a few hours ago (kind of)...try this:

example:

someIntList.ForEach(i=>i+5);

ForEach() is one of the built in .NET methods

This will modify the list, as opposed to returning a new one.

Answer 2

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 => foo.fooID + 1);

Answer 3

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<T>.AsParallel().ForAll( Action<T> / Delegate / Lambda )

For example:

var numbers = new[] { 1, 2, 3, 4, 5 };
numbers.AsParallel().ForAll( Console.WriteLine );

HTH.

Answer 4

A common way to approach this is to add your own ForEach generic method on IEnumerable<T>. Here's the one we've got in MoreLINQ:

public static void ForEach<T>(this IEnumerable<T> source, Action<T> 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 => person.Age < 21)
      .ForEach(person => person.EjectFromBar());

Answer 5

Or you can hack it up.

Items.All(p => { p.IsAwesome = true; return true; });

Answer 6

I found some way to perform in on dictionary contain my custom class methods

foreach (var item in this.Values.Where(p => p.IsActive == false))
            item.Refresh();

Where 'this' derived from : Dictionary<string, MyCustomClass>

class MyCustomClass 
{
   public void Refresh(){}
}