制作多种类型的泛型 [英] Making Generics with many types

问题描述

我有一段代码，有时候我需要创建一个新的泛型类型，但是泛型参数数量不确定。例如：

I have a chunk of code where sometimes I need to create a new generic type, but with an unknown number of generic parameters. For example:

public object MakeGenericAction(Type[] types)
{
  return typeof(Action<>).MakeGenericType(paramTypes);
}

问题是如果我的数组中有多个Type，那么该程序将崩溃。在短期内，我想出了这样的一个止损。

The problem is that if I have more than one Type in my array, then the program will crash. In the short term I have come up with something like this as a stop-gap.

public object MakeGenericAction(Type[] types)
{
  if (types.Length == 1)
  {
    return typeof(Action<>).MakeGenericType(paramTypes);
  }
  else if (types.Length ==2)
  {
    return typeof(Action<,>).MakeGenericType(paramTypes);
  }
  ..... And so on....
}

这确实有效，并且很容易覆盖我的场景，但它看起来非常黑。有没有更好的方法来处理这个问题？

This does work, and is easy enough to cover my scenarios, but it seems really hacky. Is there a better way to handle this?

推荐答案

在这种情况下，是的：

Type actionType = Expression.GetActionType(types);

这里的问题是您可能会使用DynamicInvoke，这很慢。

The problem here though is that you will probably be using DynamicInvoke which is slow.

An Action< object []> ，那么索引访问可能优于 Action< ...> ; 用DynamicInvoke

An Action<object[]> then access by index may outperform an Action<...> invoked with DynamicInvoke

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