rspec/rules/S2971/csharp/rule.adoc

== Why is this an issue?

In the interests of readability, code that can be simplified should be simplified. To that end, there are several ways ``++IEnumerable++`` language integrated queries (LINQ) can be simplified

* Use ``++OfType++`` instead of using ``++Select++`` with ``++as++`` to type cast elements and then null-checking in a query expression to choose elements based on type.
* Use ``++OfType++`` instead of using ``++Where++`` and the ``++is++`` operator, followed by a cast in a ``++Select++``
* Use an expression in ``++Any++`` instead of ``++Where(element => [expression]).Any()++``.
* Use ``++Count++`` instead of ``++Count()++`` when it's available.
* Don't call ``++ToArray()++`` or ``++ToList()++`` in the middle of a query chain.

Using ``++EntityFramework++`` may require enforcing client evaluations. Such queries should use ``++AsEnumerable()++`` instead of ``++ToArray()++`` or ``++ToList()++`` in the middle of a query chain.


=== Noncompliant code example

[source,csharp]
----
seq1.Select(element => element as T).Any(element => element != null);  // Noncompliant; use OfType
seq2.Select(element => element as T).Any(element => element != null && CheckCondition(element));  // Noncompliant; use OfType
seq3.Where(element => element is T).Select(element => element as T); // Noncompliant; use OfType
seq4.Where(element => element is T).Select(element => (T)element); // Noncompliant; use OfType
seq5.Where(element => [expression]).Any();  // Noncompliant; use Any([expression])

var num = seq6.Count(); // Noncompliant
var arr = seq.ToList().ToArray(); //Noncompliant
var count = seq.ToList().Count(x=>[condition]); //Noncompliant
----


=== Compliant solution

[source,csharp]
----
seq1.OfType<T>().Any();
seq2.OfType<T>().Any(element => CheckCondition(element));
seq3.OfType<T>();
seq4.OfType<T>();
seq5.Any(element => [expression])

var num = seq6.Count;
var arr = seq.ToArray();
var count = seq.Count(x=>[condition]); 
----


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'''
== Implementation Specification
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include::message.adoc[]

'''
== Comments And Links
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include::comments-and-links.adoc[]
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