Combining collections of different types with LINQ

Question

Let's say I have these 2 arrays:

const int length = 5;
var ints = new int[length] { 1, 2, 3, 4, 5 };
var strings = new string[length] { "s1", "s2", "s3", "s4", "s5" };

I want to loop over these and instead of this

for (var index = 0; index < length; index++)
{
    var i = ints[index];
    var s = strings[index];
    DoSomething(i, s);
}

I wonder if I, using LINQ, could somehow achieve something like this

var items = ... i in ints
            ... s in strings
            select new { I = i, S = s };

foreach (var item in items)
{
    DoSomething(item.I, item.S);
}

Just doing a nested from like this doesn't work

var items = from i in ints
            from s in strings
            select new { I = i, S = s };

since that will repeat the inner from for each outer iteration.

Answer 1

As suggested by @CharlesNRice, you can use LINQ Zip like this :

var items = ints.Zip(strings, (i, s) => new {I = i, S = s});

Answer 2

You want linq Zip. For example check this site http://jesseliberty.com/2011/06/13/the-linq-zip-operator/

I'm still going to add an example just to point something out. Zip will always goes to the shortest length. Even with the ints at 6 it will still return back just 5. I know in your example you had them the same but just passing on information about linq's Zip.

var ints = new int[] { 1, 2, 3, 4, 5, 6 };
var strings = new string[] { "s1", "s2", "s3", "s4", "s5" };
var zipper = ints.Zip(strings, (i, s) => new {i, s});

Answer 3

I see people creating a new object but no one is showing how to invoke DoSomething.

I believe this is what you want:

ints.Zip(strings, (i,s) => DoSomething(i,s));

As Grant points out you would need the following if DoSomething returns void:

ints.Zip(strings, (i,s) => { DoSomething(i,s); return 0;} );

It is also important to remember that Linq is lazy! Nothing will happen before you actually cause this code to run. So for example:

var a = ints.Zip(strings, (i,s) => { DoSomething(i,s); return 0;} );

Will not cause DoSomething to be called. However

a.ToList();

or

a.Count();

Will cause DoSomething to be called for all values.

You could also just add ToList() or Count() to the end of the first statement, so this is the best answer to your question:

ints.Zip(strings, (i,s) => { DoSomething(i,s); return 0;} ).Count();

Answer 4

This can also be done using Select method:

ints.Select((x,idx) => new { I = x, S = strings[idx] });