Concat benchmarks

Program.cs

using BenchmarkDotNet.Attributes;
using BenchmarkDotNet.Running;

namespace Benchmarks;

public class Program
{
    public static int Main(string[] args)
    {
        var summary = BenchmarkRunner.Run<ConcatImplementations>();
        return 0;
    }

}

public class ConcatImplementations { 

    [Benchmark]
    public void IEnumerableConcat()
    {
        IEnumerable<string> args = new[] { "x", "y", "z" };
        args = new[] { "a", "b" }.Concat(args);
        // materialize
        _ = args.ToArray();
    }

    [Benchmark]
    public void ListInsertRange()
    {
        List<string> args = new() { "x", "y", "z" };
        args.InsertRange(0, new[] { "a", "b" });
        // convert
        _ = args.ToArray();
    }
}

Method	Mean	Error	StdDev
IEnumerableConcat	157.4 ns	3.14 ns	4.79 ns
ListInsertRange	110.6 ns	2.20 ns	3.01 ns