org.sonar.plugins.csharp.S6613.html Maven / Gradle / Ivy
Why is this an issue?
Both the Enumerable.First extension method and the LinkedList<T>.First property can be used to find the first value
in a LinkedList<T>. However, LinkedList<T>.First is much faster than Enumerable.First. For small
collections, the performance difference may be minor, but for large collections, it can be noticeable. The same applies for the Last
property as well.
Applies to:
What is the potential impact?
We measured a significant improvement both in execution time and memory allocation. For more details see the Benchmarks section from
the More info tab.
How to fix it
The First and Last properties are defined on the LinkedList class, and the extension method call can be
replaced by calling the propery instead.
Code examples
Noncompliant code example
int GetFirst(LinkedList<int> data) =>
data.First();
int GetLast(LinkedList<int> data) =>
data.Last();
Compliant solution
int GetFirst(LinkedList<int> data) =>
data.First.Value;
int GetLast(LinkedList<int> data) =>
data.Last.Value;
Resources
Documentation
Benchmarks
Method
Runtime
Mean
Standard Deviation
Allocated
LastMethod
.NET 7.0
919,577,629.0 ns
44,299,688.61 ns
48504 B
LastProperty
.NET 7.0
271.8 ns
15.63 ns
-
LastMethod
.NET Framework 4.6.2
810,316,427.1 ns
47,768,482.31 ns
57344 B
LastProperty
.NET Framework 4.6.2
372.0 ns
13.38 ns
-
Glossary
The results were generated by running the following snippet with BenchmarkDotNet:
private LinkedList<int> data;
private Random random = new Random();
[Params(100_000)]
public int Size { get; set; }
[Params(1_000)]
public int Runs { get; set; }
[GlobalSetup]
public void Setup() =>
data = new LinkedList<int>(Enumerable.Range(0, Size).Select(x => random.Next()));
[Benchmark(Baseline = true)]
public void LastMethod()
{
for (var i = 0; i < Runs; i++)
{
_ = data.Last(); // Enumerable.Last()
}
}
[Benchmark]
public void LastProperty()
{
for (var i = 0; i < Runs; i++)
{
_ = data.Last; // Last property
}
}
Hardware configuration:
BenchmarkDotNet=v0.13.5, OS=Windows 10 (10.0.19045.2846/22H2/2022Update)
11th Gen Intel Core i7-11850H 2.50GHz, 1 CPU, 16 logical and 8 physical cores
[Host] : .NET Framework 4.8 (4.8.4614.0), X64 RyuJIT VectorSize=256
.NET 7.0 : .NET 7.0.5 (7.0.523.17405), X64 RyuJIT AVX2
.NET Framework 4.6.2 : .NET Framework 4.8 (4.8.4614.0), X64 RyuJIT VectorSize=256