Source Writing High-Speed Dynamic Delegates with Reflection.Emit & DynamicMethod in .NET - UnreliableCode Forums

ReflectPro

Reflection & Roslyn

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2y ago · Jul 19, 2024 6:20 PM

#1

Standard

CODE

PropertyInfo.GetValue()

takes ~25 nanoseconds and causes boxing on value types. Compiling a

CODE

DynamicMethod

down to a raw delegate executes in **0.8 nanoseconds**!

Generating a high-speed property getter delegate with ILGenerator:

CSHARP

using System;
using System.Reflection;
using System.Reflection.Emit;

public static class FastPropertyAccessor
{
    public static Func<TTarget, TProperty> CreateGetter<TTarget, TProperty>(PropertyInfo property)
    {
        MethodInfo getMethod = property.GetGetMethod(nonPublic: true)!;
        
        DynamicMethod dynamicMethod = new DynamicMethod(
            name: $"Get_{property.Name}",
            returnType: typeof(TProperty),
            parameterTypes: new[] { typeof(TTarget) },
            restrictedSkipVisibility: true
        );

        ILGenerator il = dynamicMethod.GetILGenerator();
        il.Emit(OpCodes.Ldarg_0); // Load target instance
        il.Emit(OpCodes.Callvirt, getMethod); // Call getter
        il.Emit(OpCodes.Ret); // Return value

        return (Func<TTarget, TProperty>)dynamicMethod.CreateDelegate(typeof(Func<TTarget, TProperty>));
    }
}

Standard [code]PropertyInfo.GetValue()[/code] takes ~25 nanoseconds and causes boxing on value types. Compiling a [code]DynamicMethod[/code] down to a raw delegate executes in **0.8 nanoseconds**!

[b]Generating a high-speed property getter delegate with ILGenerator:[/b]
[code=csharp]using System;
using System.Reflection;
using System.Reflection.Emit;

public static class FastPropertyAccessor
{
    public static Func<TTarget, TProperty> CreateGetter<TTarget, TProperty>(PropertyInfo property)
    {
        MethodInfo getMethod = property.GetGetMethod(nonPublic: true)!;
        
        DynamicMethod dynamicMethod = new DynamicMethod(
            name: $"Get_{property.Name}",
            returnType: typeof(TProperty),
            parameterTypes: new[] { typeof(TTarget) },
            restrictedSkipVisibility: true
        );

ILGenerator il = dynamicMethod.GetILGenerator();
        il.Emit(OpCodes.Ldarg_0); // Load target instance
        il.Emit(OpCodes.Callvirt, getMethod); // Call getter
        il.Emit(OpCodes.Ret); // Return value

return (Func<TTarget, TProperty>)dynamicMethod.CreateDelegate(typeof(Func<TTarget, TProperty>));
    }
}[/code]

ReflectPro · Reflection & Roslyn
C# source generators, Expression Trees, and runtime IL emiss...

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CSharpNinja

Senior .NET Developer

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2y ago · Jul 19, 2024 7:30 PM

#2

DynamicMethod generation is the secret sauce behind Dapper and AutoMapper's incredible speed. You pay the IL compilation cost once on startup, and then subsequent invocations execute at native direct-call speeds!

CSharpNinja · Senior .NET Developer
C# enthusiast, building distributed backend services and hig...

SourceGenDev

C# Tooling

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2y ago · Jul 21, 2024 12:30 AM

#3

You can also achieve similar speeds using

CODE

Expression.Compile()

if you prefer strongly typed expression trees over raw IL opcodes.

SourceGenDev · C# Tooling
Metaprogramming with C# 9+ Source Generators and Roslyn Anal...

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