ActivatorUtilities.CreateFactory uses compiled expressions to generate a high-performance factory on CoreCLR:
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public static ObjectFactory CreateFactory( |
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[DynamicallyAccessedMembers(DynamicallyAccessedMemberTypes.PublicConstructors)] Type instanceType, |
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Type[] argumentTypes) |
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{ |
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CreateFactoryInternal(instanceType, argumentTypes, out ParameterExpression provider, out ParameterExpression argumentArray, out Expression factoryExpressionBody); |
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var factoryLambda = Expression.Lambda<Func<IServiceProvider, object?[]?, object>>( |
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factoryExpressionBody, provider, argumentArray); |
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Func<IServiceProvider, object?[]?, object>? result = factoryLambda.Compile(); |
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return result.Invoke; |
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} |
NativeAOT doesn't support compiled expressions. Expressions is now a negative:
- Expressions are interpreted, reducing performance compared to standard .NET reflection.
- System.Linq.Expressions usage increases app size
CreateFactory should check for RuntimeFeature.IsDynamicCodeSupported and provide a delegate that uses standard .NET reflection when dynamic code isn't supported.
For example:
https://github.com/dotnet/aspnetcore/blob/4d75ee9a7fbad112e29b8a1d77c7d96965f62b40/src/Shared/PropertyHelper/PropertyHelper.cs#L215-L243
