Benchmark.md

BenchmarkDotNet=v0.10.11, OS=Windows 10 Redstone 2 [1703, Creators Update] (10.0.15063.909)
Processor=Intel Core i7-4870HQ CPU 2.50GHz (Haswell), ProcessorCount=8
Frequency=2435765 Hz, Resolution=410.5486 ns, Timer=TSC
.NET Core SDK=2.1.4
  [Host]     : .NET Core 2.0.5 (Framework 4.6.26020.03), 64bit RyuJIT
  DefaultJob : .NET Core 2.0.5 (Framework 4.6.26020.03), 64bit RyuJIT

Method	Value	Mean	Error	StdDev	Scaled	Allocated
StartsWithString	****	19.4152 ns	0.1120 ns	0.1047 ns	1.00	0 B
StartsWithCharacter		0.3450 ns	0.0300 ns	0.0266 ns	0.02	0 B
FirstCharacterEquals		0.2211 ns	0.0256 ns	0.0227 ns	0.01	0 B
StartsWithString	a	86.3802 ns	1.4642 ns	1.3696 ns	1.000	0 B
StartsWithCharacter	a	0.3070 ns	0.0259 ns	0.0216 ns	0.004	0 B
FirstCharacterEquals	a	0.2181 ns	0.0406 ns	0.0569 ns	0.003	0 B
StartsWithString	{	2.3418 ns	0.0779 ns	0.0833 ns	1.00	0 B
StartsWithCharacter	{	0.2802 ns	0.0287 ns	0.0268 ns	0.12	0 B
FirstCharacterEquals	{	0.2241 ns	0.0216 ns	0.0202 ns	0.10	0 B

Program.cs

using BenchmarkDotNet.Attributes;
using BenchmarkDotNet.Running;
using System;

namespace ConsoleApp18
{
    class Program
    {
        static void Main(string[] args) =>
            BenchmarkRunner.Run<Tests>();
    }

    [MemoryDiagnoser]
    public class Tests
    {
        [Params("", "a", "{")]
        public string Value;

        [Benchmark(Baseline = true)]
        public bool StartsWithString() =>
            Value.StartsWith("{");

        [Benchmark]
        public bool StartsWithCharacter() =>
            Value.StartsWith('{');

        [Benchmark]
        public bool FirstCharacterEquals() =>
            Value.Length > 0 && Value[0] == '{';
    }
}