Analyzer suggestion : replace .OrderBy().First() with MinBy() #87921
Description
The goal of the rule is to prevent sorting a whole collection where only a min/max is required.
Here are the results of a benchmark conducted on a List<double> ranging from -N to N-1 (all integers, cast to double only to match Shuffler.Shuffle's signature) shuffled by Perfolizer.Mathematics.Randomization.Shuffler
BenchmarkDotNet=v0.13.5, OS=Windows 10 (10.0.19045.2965/22H2/2022Update)
AMD Ryzen 5 4600H with Radeon Graphics, 1 CPU, 12 logical and 6 physical cores
.NET SDK=7.0.302
[Host] : .NET 7.0.5 (7.0.523.17405), X64 RyuJIT AVX2
DefaultJob : .NET 7.0.5 (7.0.523.17405), X64 RyuJIT AVX2
| Method | N | Mean | Error | StdDev |
|---|---|---|---|---|
| OrderByFirst | 1000 | 24.81 μs | 0.038 μs | 0.034 μs |
| MinBy | 1000 | 17.77 μs | 0.108 μs | 0.096 μs |
| OrderByDescendingLast | 1000 | 23.87 μs | 0.068 μs | 0.060 μs |
| OrderByDescendingFirst | 1000 | 25.37 μs | 0.063 μs | 0.059 μs |
| MaxBy | 1000 | 17.71 μs | 0.028 μs | 0.023 μs |
| OrderByLast | 1000 | 24.49 μs | 0.093 μs | 0.078 μs |
| OrderByFirst | 10000 | 250.73 μs | 3.916 μs | 3.472 μs |
| MinBy | 10000 | 189.40 μs | 1.198 μs | 1.000 μs |
| OrderByDescendingLast | 10000 | 247.57 μs | 0.478 μs | 0.447 μs |
| OrderByDescendingFirst | 10000 | 252.70 μs | 0.899 μs | 0.751 μs |
| MaxBy | 10000 | 166.38 μs | 0.046 μs | 0.036 μs |
| OrderByLast | 10000 | 243.11 μs | 0.961 μs | 0.852 μs |
I have identified the following cases :
OrderBy(...).First()=>MinBy(...)OrderBy(...).Last()=>MaxBy(...)OrderByDescending(...).First()=>MaxBy(...)OrderByDescending(...).Last()=>MinBy(...)
✅ You may also want to consider .ElementAt(0) the same as .First()
OrderBy(...).ThenBy(...).First() to MinBy (and same for all the variants described above) the rule should probably only apply when there's no ThenBy