使用反射或 IL 将自定义属性添加到 ReturnParameter

Question

我正在尝试使用 IL 在运行时创建一些类型。我有一个原件 MethodInfo，我必须复制它。

var parameters = OriginalMethod.GetParameters();

MethodBuilder methodBuilder = Builder.DefineMethod(
    $"<{OriginalMethod.Name}>k__BackingMethod",
    OriginalMethod.Attributes,
    CallingConventions.HasThis,
    OriginalMethod.ReturnType,
    parameters.Select(i => i.ParameterType).ToArray()
);

foreach (var attribute in OriginalMethod.GetCustomAttributesData().ToCustomAttributeBuilder())
    methodBuilder.SetCustomAttribute(attribute);

foreach (var attribute in OriginalMethod.ReturnParameter.GetCustomAttributesData().ToCustomAttributeBuilder())
    methodBuilder.SetCustomAttribute(attribute); // <---- Problem here

ILGenerator il = methodBuilder.GetILGenerator();
// Some code removed for brevity

return methodBuilder;

如您所见，我可以成功复制方法级别的自定义属性。我什至可以获取 ReturnParameter 上的属性。但是，我似乎无法向 ReturnAttribute 添加新属性。使用上面的代码，return 属性被用作常规方法属性。知道我该怎么做吗？

编辑：为 ToCustomAttributeBuilder

添加了代码

internal static CustomAttributeBuilder[] ToCustomAttributeBuilder(this IEnumerable<CustomAttributeData> CustomAttributes)
=> CustomAttributes.Select(attribute => attribute.ToCustomAttributeBuilder()).ToArray();

internal static CustomAttributeBuilder ToCustomAttributeBuilder(this CustomAttributeData CustomAttribute)
{
    var attributeArgs = CustomAttribute.ConstructorArguments.Select(a => a.Value).ToArray();

    var propertyArgs = CustomAttribute.NamedArguments.Where(i => i.MemberInfo is PropertyInfo);
    var propertyInfos = propertyArgs.Select(a => (PropertyInfo)a.MemberInfo).ToArray();
    var propertyValues = propertyArgs.Select(a => a.TypedValue.Value).ToArray();
    
    var fieldArgs = CustomAttribute.NamedArguments.Where(i => i.MemberInfo is FieldInfo);
    var namedFieldInfos = fieldArgs.Select(a => (FieldInfo)a.MemberInfo).ToArray();
    var namedFieldValues = fieldArgs.Select(a => a.TypedValue.Value).ToArray();
    
    return new CustomAttributeBuilder(CustomAttribute.Constructor, attributeArgs, propertyInfos, propertyValues, namedFieldInfos, namedFieldValues);
}

Answer 1

您需要将自定义属性应用于 return 值参数，而不是方法：

ParameterBuilder returnValueParameterBuilder = 
    methodBuilder.DefineParameter(0, ParameterAttributes.Retval, parameterName: null);

foreach (var attribute in OriginalMethod.ReturnParameter.GetCustomAttributesData()
                                                        .ToCustomAttributeBuilder())
{
    returnValueParameterBuilder.SetCustomAttribute(attribute);
}

使用反射或 IL 将自定义属性添加到 ReturnParameter

Adding custom attributes to ReturnParameter using reflection or IL

c#

reflection

reflection.emit