Benchmark related to conversation https://stackoverflow.com/a/65302363/7313094

gistfile1.txt

using BenchmarkDotNet.Attributes;
using BenchmarkDotNet.Running;
using System;
using System.Collections.Generic;

namespace ConsoleApp4
{
    public abstract class BaseType
    {
        public abstract string Type { get; set; }
    }

    public class ChildTypeA : BaseType
    {
        public override string Type { get; set; } = "ChildTypeA";
    }

    public class ChildTypeB : BaseType
    {
        public override string Type { get; set; } = "ChildTypeB";
    }

    public class ChildTypeC : BaseType
    {
        public override string Type { get; set; } = "ChildTypeC";
    }

    public class SwitchCaseStringVsPatternMatching
    {
        private const int n = 3_000_000;
        private List<BaseType> data = new List<BaseType>(n);

        public SwitchCaseStringVsPatternMatching()
        {
            var random = new Random();
            for (var i = 0; i < n; i++)
            {
                var next = random.NextDouble();
                if (next < 0.33)
                {
                    data.Add(new ChildTypeA());
                }
                else if (next < 0.66)
                {
                    data.Add(new ChildTypeB());
                }
                else
                {
                    data.Add(new ChildTypeC());
                }
            }
        }

        [Benchmark]
        public void UseGetTypeNameString()
        {
            foreach (var item in data)
            {
                var typeName = item.GetType().Name;

                switch (typeName)
                {
                    case "ChildTypeA":
                        break;
                    case "ChildTypeB":
                        break;
                    case "ChildTypeC":
                        break;
                }
            }
        }

        [Benchmark]
        public void UseTypeString()
        {
            foreach (var item in data)
            {
                var typeName = item.Type;

                switch (typeName)
                {
                    case "ChildTypeA":
                        break;
                    case "ChildTypeB":
                        break;
                    case "ChildTypeC":
                        break;
                }
            }
        }


        [Benchmark]
        public void UsePatternMatching()
        {
            foreach (var item in data)
            {
                switch (item)
                {
                    case ChildTypeA a:
                        break;
                    case ChildTypeB b:
                        break;
                    case ChildTypeC c:
                        break;
                }
            }
        }

    }

    class Program
    {
        static void Main(string[] args)
        {
            var summary = BenchmarkRunner.Run<SwitchCaseStringVsPatternMatching>();
        }
    }
}

Method	Mean	Error	StdDev
UseGetTypeNameString	132.64 ms	2.605 ms	5.437 ms
UseTypeString	90.44 ms	1.788 ms	1.914 ms
UsePatternMatching	40.62 ms	0.702 ms	0.862 ms

BenchmarkDotNet=v0.12.1, OS=Windows 10.0.19041.685 (2004/?/20H1)
Intel Core i7-2920XM CPU 2.50GHz (Sandy Bridge), 1 CPU, 8 logical and 4 physical cores
.NET Core SDK=5.0.100
[Host] : .NET Core 3.1.10 (CoreCLR 4.700.20.51601, CoreFX 4.700.20.51901), X64 RyuJIT
DefaultJob : .NET Core 3.1.10 (CoreCLR 4.700.20.51601, CoreFX 4.700.20.51901), X64 RyuJIT