Extend LINQ syntax

I can’t count the number of times I’ve written something like this:

var x = (from item in collection
         where item.foo
         select item.bar).Single()

Readability takes a nose dive, especially with complex or nested queries. There’s a lot we can do to improve what is one of C#'s most powerful features. From low-hanging fruit that are compatible with existing infrastructure like ORMs:

from item in collection
select single item.foo;

from item in collection
select first item.foo or default;

from item in collection
select sum of item.foo;

from item in collection
skip 5
select top 3 item.foo;

from item in collection
left join item2 in collection2 on item.foo equals item2.foo
select new { item, item2 };

To bits which are currently only usable by LINQ to Objects:

from item in collection
group item.foo by item.bar into grp using StringComparer.InvariantCulture
select grp;

from item in collection by idx
select "item " + item + " at index " + idx;

[MadsTorgersen]

We’ll keep this on the backlog as a reminder to consider something here.

The best proposal I’ve seen was

var x = 
    from item in collection
    where item.foo
    select item.bar
    do Single();

(Or some other keyword). The idea is to add a query operator that is like a . but with different precedence.

[alrz]

Would like to see if it can handle something like ToDictionary,

var x = 
    from item in collection
    where item.foo
    do ToDictionary(item.Key, item.Value);

i.e. the range variable is available in the do clause.