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();
}
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)
but this results in new_name
being set as "System.Reflection.Missing"
within the function.
Additionally I tried
$obj.foo($path, $null, $false)
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.
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.
You can simply omit the optional parameters in the call. I modified your example to run it in PS. For example:
$c = @"
public static class Bar {
public static void foo(string path, string new_name = null, bool save_now = true)
{
System.Console.WriteLine(path);
System.Console.WriteLine(new_name);
System.Console.WriteLine(save_now);
}
}
"@
add-type -TypeDefinition $c
[Bar]::Foo("test",[System.Management.Automation.Language.NullString]::Value,$false)
This generates the following
test
False
Test was passed explicitly, null is null and had no output, and the save_now evaluated to the default of True.
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