What is the biggest mistake people make when starting to use LINQ? [closed]

Answer 1

Speaking for myself, knowing when a sequence will be buffered or streamed is important.

Filling a buffer with large amounts of data will consume lots of memory. If possible, operations like reversing, counting, ordering, etc. should be done once the data has been reduced. In joins the left sequence is streamed and the right is buffered. When there's a significant difference in size, put the smaller one on the right.

Answer 2

I think understanding the point of the query execution is often a mistake (i.e. believing it's at the point of the query rather than at the point the data is first accessed), along with the belief that just because it compiles that it's going to run.

This in reference to Linq to SQL.

A fantastic tool for Linq is LinqPad by Joe Albahari, allowed me to learn Linq so much more quickly. If you don't have it, get it! And I'm not even on commission ;)

Answer 3

Somethings which come to mind are

• It must be slower, better use plain C#
• Trying to use it where simple C# would be more readable/manageable

Answer 4

Understanding where you go from Linq2SQL/Entities to Linq2Objects. Understanding what is and is-not being executed in the DB engine versus in your application. Knowing when you are working with in-memory objects versus the underlying Linq provider that you are using, and then knowing how to intentionally transition from Linq2SQL to Linq2Objects whenever you need to perform post-query processing leveraging C#/.NET functions not supported in your provider.

Answer 5

I totally agree with Adam Robinson, in fact the BIG mistake is that people stops on the beauty syntax not going deeper in the tech-facts, in terms of impacts or architectural views.

Sometimes people think about it as one thing when it's really another thing.. about that it's important to note Linq is a "Technology" and could be implemented in many ways, each of them could impact in different way about performance and design (for example), the basic syntax remain the same but the underlying things could changes.

Actually, starting from the great and growing implementations, there's not a complete list of best practices, the best practices could begin from:

1. understanding before what kind of implementation will be used (Linq2Sql, Linq2Objects, Linq2CSV, Linq2Excel, Linq2LDAP, Linq2JSON, Linq2Xml, Linq2Xsd and more)
2. then trying to understand what the basic technology features are intended in the choosed implementation

Answer 6

LINQ as a language is pretty straight forward and not so unexpected, especially if you're familiar with functional programming.

The concept of Deferred Execution is probably the biggest gotcha, and one of the best features. When you use LINQ that returns an IQueryable it's important to remember you are NOT executing whatever code you just wrote. It isn't until you call one of the methods that produces some other result that the query is executed.

Also, in terms of the LINQ to SQL provider, the biggest gotcha I've found is the performance cost. Turns out there is significant CPU cost to constructing SQL queries that are incurred every time the LINQ query is ran, unless you pre-compile your highly trafficked queries.