如何创建一个方面检查的所有方法在一个类中postsharp空引用 [英] How to create an aspect checking for null references on all methods in a class in postsharp

问题描述

如何创建一个方面检查上一类postsharp所有方法空引用。

How to create an aspect checking for null references on all methods in a class in postsharp.

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;

namespace test
{
    [MethodParameterNullCheck]
    internal class Class
    {
    	public Class()
    	{

    	}

    	public void MethodA(int i, ClassA a, ClassB b)
    	{
              //Some business logic
    	}
    }
}

纵横[MethodParameterNullCheck]应该然后展开以下code：

The aspect [MethodParameterNullCheck] should then unfold to the following code:

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;

namespace test
{
    [MethodParameterNullCheck]
    internal class Class
    {
    	public Class()
    	{

    	}

    	public void MethodA(int i, ClassA a, ClassB b)
    	{
    		if (a == null) throw new ArgumentNullException("Class->MethodA: Argument a of ClassA is not allowed to be null.");
    		if (b == null) throw new ArgumentNullException("Class->MethodA: Argument b of ClassB is not allowed to be null.");
    		// Some Business Logic
    	}
    }
}

我会AP preciate，如果你能给我这个示例实现，让我startet对AOP与postsharp。

I will appreciate if you can give me a sample implementation on this to get me startet on AOP with postsharp.

推荐答案

另一种方法是一个扩展方法：

An alternative approach is an extension method:

public static void ThrowIfNull<T>(this T obj, string parameterName) where T : class
{
    if(obj == null) throw new ArgumentNullException(parameterName);
}

然后调用：

foo.ThrowIfNull("foo");
bar.ThrowIfNull("bar");

在 T：类 pervents我们意外拳击整型等

The T : class pervents us accidentally boxing ints etc.

重新AOP;乔恩斯基特有类似的东西<一个样本href="http://msmvps.com/blogs/jon_skeet/archive/2008/03/27/postsharp-and-iterator-blocks-a-beautiful-combination.aspx"相对=nofollow>此处 - 但涵盖了一个方法/参数

Re AOP; Jon Skeet has a sample for something similar here - but covering a single method/parameter.

下面是转载的方面;注意，这方面只覆盖一次一个说法，并且是方法而异，但一般我认为这是完全合理的。不过，你也许可以改变它。

Here's the aspect reproduced; note that this aspect covers only 1 argument at a time, and is method-specific, but in general I'd argue that this is perfectly reasonable... however, you could probably change it.

using System;
using System.Reflection;
using PostSharp.Laos;

namespace IteratorBlocks
{
    [Serializable]
    class NullArgumentAspect : OnMethodBoundaryAspect
    {
        string name;
        int position;

        public NullArgumentAspect(string name)
        {
            this.name = name;
        }

        public override void CompileTimeInitialize(MethodBase method)
        {
            base.CompileTimeInitialize(method);
            ParameterInfo[] parameters = method.GetParameters();
            for (int index = 0; index < parameters.Length; index++)
            {
                if (parameters[index].Name == name)
                {
                    position = index;
                    return;
                }
            }
            throw new ArgumentException("No parameter with name " + name);
        }

        public override void OnEntry(MethodExecutionEventArgs eventArgs)
        {
            if (eventArgs.GetArguments()[position] == null)
            {
                throw new ArgumentNullException(name);
            }
        }
    }
}

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