为什么不能System.Array的是一个类型的约束？ [英] Why can't System.Array be a type constraint?

问题描述

我工作的一个小项目，有一些不同类型的数组（如双[] ，浮法[] ， INT [] 。为了验证/测试/神智的目的，我打印出一些阵列的控制台，因为我走。所以我有多个看起来像下面的这些功能​​（简化这个例子 - 假设我只用一维数组处理）：

I'm working on a small project with a few different types of arrays (e.g. double[], float[], int[]. For verification / testing / sanity purposes, I'm printing out some of these arrays to the console as I go along. So I have multiple functions that look like these below (simplified for this example - assume I'm only dealing with single-dimension arrays):

void Print(float[] a) // prints an array of floats
{
    for (int i = 0; i < a.Length; i++)
    {
        Console.Write(a[i]);
    }
}

void Print(double[] a) // prints an array of doubles
{
    for (int i = 0; i < a.Length; i++)
    {
        Console.Write(a[i]);
    }
}

我，在我无穷的智慧，以为我可以简单地创建这些功能的通用版本减少一些code重复。所以，我想这样的：

I, in my infinite wisdom, thought I could reduce some of the code duplication by simply creating a generic version of these functions. So I tried this:

void Print<T>(T t) where T : Array
{
    for (int i = 0; i < t.Length; i++)
    {
        Console.Write(t.GetValue(i));
    }
}

智能感知是没有抱怨，但是编译器失败，一个很有趣的错误：

Intellisense isn't complaining, but the compiler fails with a very interesting error:

约束不能成为特殊阶层的System.Array

我看了一个解释（类似于对象或密封类，但没有发现太多，除了一提的on MSDN 。任何人都可以向我解释的为什么的是这种情况？为什么我不能指定类型的System.Array ？

I've looked for an explanation (similar to Object or sealed classes, but haven't found much, besides a mention on msdn. Can anyone explain to me why this is the case? Why can't I specify a type constraint of System.Array?

PS：虽然打字了这一点，我意识到，我可以完成我本来想更轻松，像这样一个简单的功能：

p.s.: While typing this out, I realized that I can accomplish what I originally wanted more easily, with a simple function like this:

void Print(System.Array a)
{
    for (int i = 0; i < a.Length; i++)
    {
        Console.Write(a.GetValue(i));
    }
}

这是为什么有在编译器？

Is this why there's a special rule for arrays in the compiler?

推荐答案

适当的语法，做你想做的是这样的：

The appropriate syntax to do what you want is this:

void Print<T>(T[] array)
{
    for (int i = 0; i < array.Length; i++)
    {
        Console.Write(array[i]);
    }
}

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