Linq Cast vs OfType

cast-vs-oftype.md

With BencharkDot net, this benchmark creates a list of 10,000 strings then tests either OfType<T> or Cast<T>

Here's the benchmark code:

/// <summary>
/// Want to check what is faster OfType or Cast when a enurable all has the same items
/// </summary>
[Config(typeof(Config))]
public class LinqCastBenchmarks
{
    private class Config : ManualConfig
    {
        public Config()
        {
            Add(new MemoryDiagnoser());
        }
    }

    public LinqCastBenchmarks()
    {
        _array = new List<object>();
        _array.AddRange(Enumerable.Range(0, 10000).Select(x => x.ToString()));
    }

    private readonly List<object> _array;

    [Benchmark(Baseline = true)]
    public void OfType()
    {
        foreach (var i in _array.OfType<string>())
        {
            var a = i;
        }
    }

    [Benchmark()]
    public void Cast()
    {
        foreach (var i in _array.Cast<string>())
        {
            var a = i;
        }
    }

    [Benchmark()]
    public void ExplicitCast()
    {
        foreach (var i in _array)
        {
            var a = (string)i;
        }
    }

Host Process Environment Information:
BenchmarkDotNet.Core=v0.9.9.0
OS=Microsoft Windows NT 6.2.9200.0
Processor=Intel(R) Core(TM) i7-4710HQ CPU 2.50GHz, ProcessorCount=8
Frequency=2435769 ticks, Resolution=410.5480 ns, Timer=TSC
CLR=MS.NET 4.0.30319.42000, Arch=32-bit RELEASE
GC=Concurrent Workstation
JitModules=clrjit-v4.6.1586.0

Type=LinqCastBenchmarks  Mode=Throughput  

   Method |      Median |    StdDev | Scaled | Scaled-SD | Gen 0 | Gen 1 | Gen 2 | Bytes Allocated/Op |

------------- |------------ |---------- |------- |---------- |------ |------ |------ |------------------- | OfType | 254.8104 us | 4.9054 us | 1.00 | 0.00 | - | - | - | 41.13 | Cast | 210.4970 us | 7.5344 us | 0.84 | 0.03 | - | - | - | 43.58 | ExplicitCast | 44.1904 us | 1.2827 us | 0.17 | 0.01 | - | - | - | 2.47 |