从PowerShell中调用C＃方法不提供可选的参数 [英] call C# method from powershell without supplying optional arguments

问题描述

我有一个C＃方法，我从DLL加载带有可选的字符串参数的默认值空。例如：

I have a c# method I am loading from a dll with optional string arguments that default to null. For example

public void foo(string path, string new_name = null, bool save_now = true)
{
    if(name == null)
        new_name = Path.GetFileNameWithoutExtension(path);
    ...
    if(save_now)
       Save();
}

我想从一个PowerShell脚本中调用这个，而不是为了提供一个值 NEW_NAME ，但一个 save_now 。按照这个看似非常类似的问题我已经试过

I want to call this from within a powershell script and not supply a value for new_name but one for save_now. As per this seemingly very similar question I have tried

$default = [type]::Missing
$obj.foo($path, $default, $false)

但这会导致 NEW_NAME 被设置为System.Reflection.Missing在函数中。

but this results in new_name being set as "System.Reflection.Missing" within the function.

此外我试过

$obj.foo($path, $null, $false)

但这会导致 NEW_NAME 被设置为空字符串，仍然不是空。我可以设置默认为空字符串，但我想知道是否有真正有使用默认值的好方法。

but this results in new_name being set to the empty string, still not null. I could set the default to the empty string, but I was wondering if there was any good way to actually have the default value be used.

推荐答案

没有可以在PowerShell中做。它不支持C＃/ VB可选参数。这是在调用方法时程序员不和PowerShell只是没有做到这一点提供的缺省值语言的职责。

No can do in PowerShell. It doesn't support C#/VB optional parameters. It is the duty of the language calling the method to provide the default values when the programmer doesn't and PowerShell just doesn't do that.

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