带有引用参数/参数或匿名函数的 Func/Action 委托 [英] Func / Action delegates with reference arguments/parameters or anonymous functions

问题描述

我只是想知道，委托和内联 lambda 函数的 ref 和 out 参数的确切语法如何.

I just wondered, how the exact syntax is for ref and out parameters for delegates and inline lambda functions.

这是一个例子

如果一个函数被定义为

 public void DoSomething(int withValue) { } 

可以通过以下方式创建函数中的委托

a delegate in a function can be created by

 public void f()
 {   
     Action<int> f2 = DoSomething;
     f2(3);
 }

如果原始函数被定义为

how is that syntax, if the original function would be defined as

 public void DoSomething(ref int withValue) { withValue = 3; } 

推荐答案

你需要为这个方法签名定义一个新的委托类型:

You need to define a new delegate type for this method signature:

delegate void RefAction<in T>(ref T obj);

public void F()
{
    RefAction<int> f2 = DoSomething;
    int x = 0;
    f2(ref x);
}

.NET Framework 不包含这种类型的原因可能是因为 ref 参数不是很常见，如果为每种可能的组合添加一个委托类型，所需类型的数量会爆炸式增长.

The reason why the .NET Framework does not include this type is probably because ref parameters are not very common, and the number of needed types explodes if you add one delegate type for each possible combination.

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