Can we update external variable through LINQ?

Question

Can we update external variable through linq, i.e., can we update a variable which is not being used in linq's scope through a linq?

For example, this is what I tried:

var s = list_UIModes_And_Related_Actions_Details
  .Select(x => x.ActionIdList)
  .Select(y => modeAndActionRelationTable[Counter++] = Convert.ToByte(y));

But this line doesn't update modeAndActionRelationTable array.

What have you tried? What was the result of doing so? What does your research indicate? — Flater, Feb 19 '18 at 10:13
This question is going to mark as closed. be quick if you want to add anything more for clarification — sujith karivelil, Feb 19 '18 at 10:17
What happens if you add `.ToList()` at the end of the last line? — mjwills, Feb 19 '18 at 10:23
`modeAndActionRelationTable[Counter++]` is a minefield, beware can lead to unexpected errors — Mrinal Kamboj, Feb 19 '18 at 10:33

score 4 · Answer 1 · answered Feb 19 '18 at 10:20

Yes, you can change any variable inside your LINQ statement, but you should refrain from doing so.

In your example, if you walk over the enumerable s twice, Counter will go out of bounds. If it iterates only half way, and starts over, Counter will be off too. It is just not reliable.

Your code will probably work the first time you materialize the enumerable entirely. Adding ToList() or ToArray() will do that for you.

Can we update external variable through LINQ?

1 Answers1