LINQ, simplifying expression - take while sum of taken does not exceed given value

Question

Given a setup like this ..

class Product {
   int Cost;
   // other properties unimportant
}

var products = new List {
    new Product { Cost         


        

Answer 1

You can do this if you want a solution without an external variable

var indexQuery = products.Select((x,index) => new { Obj = x, Index = index });

var query = from p in indexQuery 
            let RunningTotal = indexQuery.Where(x => x.Index <= p.Index)
                                         .Sum(x => x.Obj.Cost)
            where credit >= RunningTotal
            select p.Obj;