如何使用 PostSharp 实现延迟加载? [英] How to implement Lazy loading with PostSharp?

问题描述

我想使用 PostSharp 在属性上实现延迟加载.

I would like to implement lazy loading on properties with PostSharp.

简而言之，而不是写作

SomeType _field = null;
private SomeType Field
{
    get
    {
        if (_field == null)
        {
            _field = LongOperation();
        }
        return _field;
    }
}

我想写

[LazyLoadAspect]
private object Field
{
    get
    {
        return LongOperation();
    }
}

因此，我确定我需要在类中发出一些代码来生成支持字段，以及在 getter 方法中以实现测试.

So, I identify that I need to emit some code in the class to generate the backing field, as well as inside the getter method in order to implement the test.

使用 PostSharp，我正在考虑覆盖 CompileTimeInitialize，但我缺少处理已编译代码的知识.

With PostSharp, I was considering overriding CompileTimeInitialize, but I am missing the knowledge to get a handle over the compiled code.

该问题可以扩展到任何无参数方法，例如:

The question can be extended to any parameterless method like:

SomeType _lazyLoadedField = null;
SomeType LazyLoadableMethod ()
{
    if(_lazyLoadedField ==null)
    {
        // Long operations code...
        _lazyLoadedField = someType;
    }
    return _lazyLoadedField ;
}

会变成

[LazyLoad]
SomeType LazyLoadableMethod ()
{
     // Long operations code...
     return someType;
}

推荐答案

经过我们的评论，我想我现在知道你想要什么了.

After our comments, I think I know what you want now.

[Serializable]
    public class LazyLoadGetter : LocationInterceptionAspect, IInstanceScopedAspect
    {
        private object backing;

        public override void OnGetValue(LocationInterceptionArgs args)
        {
            if (backing == null)
            {
                args.ProceedGetValue();
                backing = args.Value;
            }

            args.Value = backing;
        }

        public object CreateInstance(AdviceArgs adviceArgs)
        {
            return this.MemberwiseClone();
        }

        public void RuntimeInitializeInstance()
        {

        }
    }

测试代码

public class test
    {
        [LazyLoadGetter]
        public int MyProperty { get { return LongOperation(); } }
    }

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