c# qr codes Will LINQ to Objects hurt the performance of my code in C#.NET

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Will LINQ to Objects hurt the performance of my code
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Sometimes LINQ to Objects does not provide what you need right from the box. Let s consider a fairly common scenario that Jon Skeet, author of C# in Depth and a C# MVP, presents on his blog.6 Imagine you have a collection of objects and you need to find the object that has the maximum value for a certain property. This is like having a box full of cookies and you want to find the one that has the most chocolate chips not for you, but to offer it to your darling, of course. The box of cookies is the collection, and the number of chocolate chip s is the property. At first, you might think that the Max operator, which is part of the standard query operators, is all you need. But the Max operator doesn t help in this case
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See http://msmvps.com/blogs/jon.skeet/archive/2005/10/02/68712.aspx.
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Beyond basic in-memory queries
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because it returns the maximum value, not the object that has that value. Max can tell you the maximum number of chocolate chips on one cookie, but cannot tell you which cookie this is! This is a typical scenario where we have the choice among several options, including using LINQ in one way or another or resorting to LINQ-free code and classical constructs. Like Jon Skeet, let s review possible ways to find a replacement for the inadequate Max. Options A first option is to use a simple foreach loop, as in listing 5.31.
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Listing 5.31 Using a foreach statement to find the book with the highest number of pages in a collection
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Book maxBook = null; foreach (var book in books) { if ((maxBook == null) || (book.PageCount > maxBook.PageCount)) maxBook = book; }
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This solution is pretty straightforward. It keeps a reference to the maximum element so far . It iterates through the list only once. It has a complexity of O(n), which is mathematically the best we can get without knowing something about the list. A second option is to sort the collection and take the first element, as in listing 5.32.
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Listing 5.32 Using sorting and First to find the book with the highest number of pages in a collection
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var sortedList = from book in books orderby book.PageCount descending select book; var maxBook = sortedList.First();
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In this solution, we use a LINQ query to sort the books in descending number of pages, and then take the first book in the resulting list. The disadvantage with this approach is that all the books are sorted before we can get the result. This operation is likely to be O(n log n).
Performance considerations
A third option is to use a use a subquery, as in listing 5.33.
Listing 5.33 Using a subquery to find the book with the highest number of pages in a collection
var maxList = from book in books where book.PageCount == books.Max(b => b.PageCount) select book; var maxBook = maxList.First();
This goes through the list, finding every book whose number of pages is equal to the maximum, and then takes the first of those books. Unfortunately, the comparison calculates the maximum size on every iteration. This makes it an O(n2) operation. A fourth option is to use two separate queries, like in listing 5.34.
Listing 5.34 Using two separate queries to find the book with the highest number of pages in a collection
var maxPageCount = books.Max(book => book.PageCount); var maxList = from book in books where book.PageCount == maxPageCount select book; var maxBook = maxList.First();
This is similar to the previous version, but solves the problem of the repeated calculation of the maximum number of pages by doing it before anything else. This makes the whole operation O(n), but it s somewhat dissatisfying, as we have to iterate the list twice. The last solution we d recommend for its higher integration with LINQ is to create a custom query operator. Listing 5.35 shows how to code such an operator, which we ll call MaxElement.
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