Add new benchmark for reusing record type and fix boxing

performance/CsvHelper.Benchmarks/BenchmarkEnumerateRecordsSingleInstance.cs

@@ -0,0 +1,60 @@
+using System;
+using System.Globalization;
+using System.IO;
+using BenchmarkDotNet.Attributes;
+
+namespace CsvHelper.Benchmarks;
+
+[MemoryDiagnoser]
+public class BenchmarkEnumerateRecordsSingleInstance
+{
+    private const int entryCount = 2000;
+    private readonly MemoryStream stream = new();
+
+    public class SimpleWithValueType
+    {
+        public int Id { get; set; }
+        public bool Flag1 { get; set; }
+        public bool Flag2 { get; set; }
+    }
+
+    [GlobalSetup]
+    public void GlobalSetupSimple()
+    {
+        using var streamWriter = new StreamWriter(this.stream, null, -1, true);
+        using var writer = new CsvWriter(streamWriter, CultureInfo.InvariantCulture, true);
+        var random = new Random(43); // Different seed for variety
+
+        writer.WriteHeader(typeof(SimpleWithValueType));
+        writer.NextRecord();
+        for (int i = 0; i < entryCount; ++i)
+        {
+            writer.WriteRecord(new SimpleWithValueType()
+            {
+                Id = random.Next(),
+                Flag1 = random.Next(2) == 0,
+                Flag2 = random.Next(2) == 0
+            });
+            writer.NextRecord();
+        }
+    }
+
+    [GlobalCleanup]
+    public void GlobalCleanupSimple()
+    {
+        this.stream.Dispose();
+    }
+
+    [Benchmark]
+    public void EnumerateRecordsSingleInstance()
+    {
+        this.stream.Position = 0;
+        using var streamReader = new StreamReader(this.stream, null, true, -1, true);
+        using var csv = new CsvReader(streamReader, CultureInfo.InvariantCulture, true);
+        var instance = new SimpleWithValueType();
+        foreach (var record in csv.EnumerateRecords(instance))
+        {
+            _ = record;
+        }
+    }
+}

performance/CsvHelper.Benchmarks/BenchmarkMain.cs

@@ -4,8 +4,8 @@ namespace CsvHelper.Benchmarks;
 
 internal class BenchmarkMain
 {
-	static void Main(string[] args)
-	{
-		_ = BenchmarkRunner.Run<BenchmarkEnumerateRecords>();
-	}
+    static void Main(string[] args)
+    {
+		_ = BenchmarkSwitcher.FromAssembly(System.Reflection.Assembly.GetExecutingAssembly()).Run(args);
+    }
 }

performance/CsvHelper.Benchmarks/CsvHelper.Benchmarks.csproj

@@ -7,6 +7,7 @@
 
   <ItemGroup>
     <PackageReference Include="BenchmarkDotNet" Version="0.15.0" />
+    <PackageReference Include="Microsoft.VisualStudio.DiagnosticsHub.BenchmarkDotNetDiagnosers" Version="18.0.36421.1" />
   </ItemGroup>
 
   <ItemGroup>

src/CsvHelper/TypeConversion/BooleanConverter.cs

@@ -12,59 +12,62 @@ namespace CsvHelper.TypeConversion;
 /// </summary>
 public class BooleanConverter : DefaultTypeConverter
 {
-	/// <inheritdoc/>
-	public override object? ConvertFromString(string? text, IReaderRow row, MemberMapData memberMapData)
-	{
-		if (bool.TryParse(text, out var b))
-		{
-			return b;
-		}
+    private static readonly object BoxedTrue = true;
+    private static readonly object BoxedFalse = false;
 
-		if (short.TryParse(text, out var sh))
-		{
-			if (sh == 0)
-			{
-				return false;
-			}
-			if (sh == 1)
-			{
-				return true;
-			}
-		}
+    /// <inheritdoc/>
+    public override object? ConvertFromString(string? text, IReaderRow row, MemberMapData memberMapData)
+    {
+        if (bool.TryParse(text, out var b))
+        {
+            return b ? BoxedTrue : BoxedFalse;
+        }
 
-		var t = (text ?? string.Empty).Trim();
-		foreach (var trueValue in memberMapData.TypeConverterOptions.BooleanTrueValues)
-		{
-			if (memberMapData.TypeConverterOptions.CultureInfo!.CompareInfo.Compare(trueValue, t, CompareOptions.IgnoreCase) == 0)
-			{
-				return true;
-			}
-		}
+        if (short.TryParse(text, out var sh))
+        {
+            if (sh == 0)
+            {
+                return BoxedFalse;
+            }
+            if (sh == 1)
+            {
+                return BoxedTrue;
+            }
+        }
 
-		foreach (var falseValue in memberMapData.TypeConverterOptions.BooleanFalseValues)
-		{
-			if (memberMapData.TypeConverterOptions.CultureInfo!.CompareInfo.Compare(falseValue, t, CompareOptions.IgnoreCase) == 0)
-			{
-				return false;
-			}
-		}
+        var t = (text ?? string.Empty).Trim();
+        foreach (var trueValue in memberMapData.TypeConverterOptions.BooleanTrueValues)
+        {
+            if (memberMapData.TypeConverterOptions.CultureInfo!.CompareInfo.Compare(trueValue, t, CompareOptions.IgnoreCase) == 0)
+            {
+                return BoxedTrue;
+            }
+        }
 
-		return base.ConvertFromString(text, row, memberMapData);
-	}
+        foreach (var falseValue in memberMapData.TypeConverterOptions.BooleanFalseValues)
+        {
+            if (memberMapData.TypeConverterOptions.CultureInfo!.CompareInfo.Compare(falseValue, t, CompareOptions.IgnoreCase) == 0)
+            {
+                return BoxedFalse;
+            }
+        }
 
-	/// <inheritdoc/>
-	public override string? ConvertToString(object? value, IWriterRow row, MemberMapData memberMapData)
-	{
+        return base.ConvertFromString(text, row, memberMapData);
+    }
+
+    /// <inheritdoc/>
+    public override string? ConvertToString(object? value, IWriterRow row, MemberMapData memberMapData)
+    {
 		var b = value as bool?;
 		if (b == true && memberMapData.TypeConverterOptions.BooleanTrueValues.Count > 0)
-		{
-			return memberMapData.TypeConverterOptions.BooleanTrueValues.First();
-		}
+        {
+            return memberMapData.TypeConverterOptions.BooleanTrueValues.First();
+        }
 		else if (b == false && memberMapData.TypeConverterOptions.BooleanFalseValues.Count > 0)
-		{
-			return memberMapData.TypeConverterOptions.BooleanFalseValues.First();
-		}
+        {
+            return memberMapData.TypeConverterOptions.BooleanFalseValues.First();
+        }
 
-		return base.ConvertToString(value, row, memberMapData);
-	}
+        return base.ConvertToString(value, row, memberMapData);
+    }
 }