FxCop的铸造警告 [英] FXCop casting Warning

问题描述

我运行的FxCop时收到以下错误：

I get the following error when running FXCop:

CA1800：Microsoft.Performance：
'的obj'，一个变量，被转换为输入
'工作'的方法
多次'ProductsController.Details（INT，
INT）。高速缓存中的'为'
运营商或直接投以
消除冗余castclass
指令

CA1800 : Microsoft.Performance : 'obj', a variable, is cast to type 'Job' multiple times in method 'ProductsController.Details(int, int)'. Cache the result of the 'as' operator or direct cast in order to eliminate the redundant castclass instruction

代码：

        object obj = repository.GetJobOrPlace(jobId);//Returns  (object) place or (object) product

        if (obj != null)
        {
            if (obj is Job)
            {
                Job j = (Job) obj;
                Debug.WriteLine(j.Title);
            }
            else if (obj is Place)
            {
                Place p = (Place) obj;
                Debug.WriteLine(p.Title);
            }
        }

这有什么错呢？我只能看见一投：工作j =（工作）目标文件

What's wrong with this? I can only see one cast: Job j = (Job) obj.

推荐答案

有只有一个的投但也有一个的测试的。所以，你可以替换第一个块：

There's only one cast but there's also a test. So you can replace the first block with:

Job j = obj as Job;
if (j != null)
{
    Debug.WriteLine(j.Title);
}

这意味着执行时间试验只需要执行一次，而不是两次。这是一个有点微优化 - 在你的情况下，它会使代码有点混乱，因为你需要：

That means the execution time test only needs to be performed once, instead of twice. It's a bit of a micro-optimisation - and in your case it would make the code a bit messier, as you'd need:

Job j = obj as Job;
if (j != null)
{
    Debug.WriteLine(j.Title);
}
else
{
    Place p = obj as Place;
    if (p != null)
    {
        Debug.WriteLine(p.Title);
    }
}

（或声明并初始化 p 更早，这浪费了测试，如果 OBJ 实际上是一个工作 ...）

(Or declare and initialize p earlier, which wastes a test if obj is actually a Job...)

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