如何调用动态类型的扩展方法？

发布于 2024-10-21 13:37:47 字数 384 浏览 2 评论 0原文

我正在阅读 Jon Skeet 的《C# in Depth, 2nd Edition》一书。他说我们可以使用两种解决方法来调用带有动态参数的扩展方法，就像

dynamic size = 5;
var numbers = Enumerable.Range(10, 10);
var error = numbers.Take(size);
var workaround1 = numbers.Take((int) size);
var workaround2 = Enumerable.Take(numbers, size);

然后他说的“如果您想使用动态值作为隐式 this 值来调用扩展方法，两种方法都可以工作” 。我不知道如何实现它。

多谢。

原文

I'm reading the book 'C# in Depth, 2nd Edition' of Jon Skeet. He said that we can call extension methods with dynamic arguments using two workarounds, just as

dynamic size = 5;
var numbers = Enumerable.Range(10, 10);
var error = numbers.Take(size);
var workaround1 = numbers.Take((int) size);
var workaround2 = Enumerable.Take(numbers, size);

Then he said "Both approaches will work if you want to call the extension method with the dynamic value as the implicit this value". I don't know how to achieve it.

Thanks a lot.

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渡你暖光 2024-10-28 13:37:47

就像这样：

dynamic numbers = Enumerable.Range(10, 10);
var firstFive = Enumerable.Take(numbers, 5);

换句话说，只需将其作为静态方法调用，而不是作为扩展方法。

或者如果你知道一个合适的类型参数，你可以直接转换它，我通常会使用一个额外的变量来做到这一点：

dynamic numbers = Enumerable.Range(10, 10);
var sequence = (IEnumerable<int>) numbers;
var firstFive = sequence.Take(5);

...但是如果你正在处理动态类型，你很可能不知道序列元素类型，在这种情况下，第一个版本基本上让“执行时编译器”弄清楚。

Like this:

dynamic numbers = Enumerable.Range(10, 10);
var firstFive = Enumerable.Take(numbers, 5);

In other words, just call it as a static method instead of as an extension method.

Or if you know an appropriate type argument you could just cast it, which I'd typically do with an extra variable:

dynamic numbers = Enumerable.Range(10, 10);
var sequence = (IEnumerable<int>) numbers;
var firstFive = sequence.Take(5);

... but if you're dealing with dynamic types, you may well not know the sequence element type, in which case the first version lets the "execution time compiler" figure it out, basically.

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