I have a method that has several overrides. In one of the more expanded overrides, I want to return an OUT parameter but not in my simpler overrides. For example:

我有一个方法，它有几个重写。在一个扩展较多的重写中，我想返回一个out参数，但不是在我的较简单重写中。例如：

public bool IsPossible(string param1, int param2)
public bool IsPossible(string param1, int param2, out bool param3)

The way I am currently achieving this, is like so:

我目前实现这一点的方式是这样的：

public bool IsPossible(string param1, int param2) {
    bool temp;
    return IsPossible(param1, param2, out temp);
}

Is there a better way to achieve this? Can I (or should I) use a null-able out parameter?

有没有更好的方法来实现这一点？我可以(或应该)使用一个可以为空的输出参数吗？

That looks fine to me. A out cannot be optional for technical reasons (it needs to point to a valid instance).

在我看来没问题。出于技术原因，out不能是可选的（它需要指向有效的实例）。

Since C# 7.0 you can pass a Discard (_) into the method:

从C# 7.0开始，你可以将一个Discard（_）传入方法：

return IsPossible(param1, param2, out _);

See: https://learn.microsoft.com/en-us/dotnet/csharp/discards

请参阅：https://learn.microsoft.com/en-us/dotnet/csharp/discards

OP:

点评：

Can I (or should I) use a null-able out parameter?

A nullable out parameter won't do you much good. This:

可为空的out参数不会对您有多大好处。这一点：

public bool IsPossible( string param1, int param2, out bool? param3 )
{
  ...
}

doesn't make param3 optional. It changes the semantics of what param3 is. A bool? (aka Nullable<bool>) widens the domain of param3 from 2 values ( true and false ) to 3, adding a third value (null), usually interpreted as missing/unknown. The caller still must supply all three arguments.

不会使参数3成为可选的。它改变了param3是什么的语义。一个bool？(也称为Nullable )将参数3的范围从2个值(TRUE和FALSE)扩大到3，添加第三个值(NULL)，通常被解释为缺失/未知。调用方仍然必须提供所有三个参数。

Overloading IsPossible() by providing an overload -- the "don't care" scenario -- that discards the reference parameter is the proper solution.

重载是可能的()，方法是提供一个重载--“无关”场景--丢弃引用参数是正确的解决方案。

A 'ref' or 'out' parameter cannot have a default value.

The way you've done it is just fine. Sorry, no silver bullet.

你做这件事的方式很好。抱歉，没有灵丹妙药。

Personally I think it is fine "as is". Another approach, though, is to return a composite return value (perhaps an immutable struct with 2 properties); that avoids the fact that some people avoid out. I am not one of those people :p

就我个人而言，我认为“原样”很好。然而，另一种方法是返回复合返回值(可能是具有两个属性的不可变结构)；这避免了一些人避免OUT的事实。我不是那种人：P

Re the question; indeed, out/ref can't be optional.

这是个问题;实际上，out/ref不能是可选的。

If you wanted to get unnecessarily fancy you could give the conposite return-type a conversion to bool to allow implicit if tests.

如果想要不必要的花哨，可以给复合的返回类型一个到bool的转换，以允许隐式的if测试。

Yes, Nullable variables are great. You would then do something like this.

是的，可为空的变量很棒。然后你会做这样的事情。

public bool? IsPossible(string param1, int param2);

var ans = IsPossible("Parm1", 1);
if (ans.HasValue)
{
   //working.
 }

Very old question. Anyway, there is another possibility.
I do like @aaroncatlin 's answer about discarded variables.

很老的问题。无论如何，还有另一种可能性。我确实喜欢@aaroncatlin‘S关于丢弃变量的回答。

But suppose the 3rd parameter is a byte[] and the caller optionally wants to return a huge number of bytes... Usually this construct is used by native API's.

但是假设第三个参数是byte[]，并且调用者可以选择返回大量字节……通常，此构造由本机API使用。

So, if the callee expects the possibility of getting a null reference, we can pass a null as 3rd parameter from an unsafe block like this:

因此，如果被调用者期望获得空引用的可能性，我们可以从不安全块中传递一个空参数作为第三个参数，如下所示：

public unsafe bool IsPossible(string param1, int param2) {
    return IsPossible(param1, param2, out *(bool*)null);
}

In this case useless. But in case of optional byte[] it does make sense.

在这种情况下没用。但在可选byte[]的情况下，它确实有意义。