LINQ¶

This chapter will handle topics about LINQ.

Using `is` and `as` instead of `OfType`¶

Using is and as cast should not be used in LINQ as it degrades readability and to some extend also performance (neglactable small under normal circumstances).

❌ Bad Less readable and unnecessary casts.

persons.Where(p => p is FullTimeEmployee).Select(p => p as FullTimeEmployee);
persons.Where(p => p is FullTimeEmployee).Select(p => (FullTimeEmployee)p);
persons.Select(p => p as FullTimeEmployee).Where(p => p != null);

✅ Good Using OfType is cleaner and more readable.

persons.OfType<FullTimeEmployee>();

Using `Count()` instead of `All` or `Any`¶

The problem with Count() is that LINQ has to enumerate every single entry in the enumeration to get the full count, where as Any/All would return immediately as soon as the condition is not satisfied anymore. In general conditions (excluding LINQ to SQL) Any/All in the worst case have the same runtime as Count but in best and average cases they are faster and more readable.

❌ Bad Less readable and unnecessary enumerations

persons.Count() > 0
persons.Count(MyPredicate) > 0
persons.Count(MyPredicate) == 0
persons.Count(MyPredicate) == persons.Count()

✅ Good More readable and avoids unnecessary enumerations

persons.Any()
persons.Any(MyPredicate)
!persons.Any(MyPredicate)
persons.All(MyPredicate)

LINQ¶

Using is and as instead of OfType¶

Using Count() instead of All or Any¶

Using `is` and `as` instead of `OfType`¶

Using `Count()` instead of `All` or `Any`¶