sandersade / common-linq-mistakes Goto Github PK

If I know that provider knows how to combine multiple Where-s then multiple Where-s improve readability quite a lot.

Long non readable && || combination can be really pain to read.

Hi,
Nice write-up! However, few comments:

Common LINQ mistakes

Reads more like Common LINQ to Entitles mistakes. Most explanations dive into resulting SQL issues. But also there are LINQ to Objects, to XML, other IQueryable implementations, to Cosmos DB, etc. which or might not have these issues, or might have different ones.

Single() methods go over all elements of the set

• Goes or will go :)
• Concerns only Single(predicate)
• Single() on all platforms basically will make just 2 iterations instead of 1. If logically or semantically there should be only a single element, it's fine to use it because the penalty is insignificant.

I am not sure why people just select the items

• Usually a left over after refactoring, indeed.
• Or to return IEnumerable instead of a concrete class, probably. There is special method ToEnumerable() but this is still a common mistake.

I don't see this one listed.

Correct solution is to use Contains, or to use SqlBulkCopy and load your IEnumerable into a temp table and join on that.

Hey,

First let me say, your article and explanations are great.
As a developer working with legacy code and old conventions/standards, I come across these mistakes daily.

I want to suggest some tips on finding these mistakes, using regular expressions:

.Single() and .SingleOrDefault()

use: \.Single(OrDefault)?\(.*\)

.First() and .FirstOrDefault()

use: \.First(OrDefault)?\(.*\)

Empty .Count()

use: \.Count\(\)

Other occurences of .Count()

use: \.Count\(.*\)
or in this case if.*\(.*\.Count\(.*\)\) might help.

.Where().First() and .Where().FirstOrDefault()

use: \.Where\(.*\)\.First(OrDefault)?\(.*\)

.Where().Where()

use: \.Where\(.*\)\.Where\(.*\)

.OrderBy().OrderBy()

use: \.OrderBy\(.*\)\.OrderBy\(.*\)

.Select(x => x)

use: \.Select\((\w)\s*=>\s*\1\)