How do I call overloaded static methods from the .

问题:

Below is a transcript of what I've tried and what happens.

I'm looking for how to call a specific overload along with an explanation of why the following does not work. If your answer is "you should use this commandlet instead" or "call it twice" please understand when I don't accept your answer.

PS C:\> [System.IO.Path]::Combine("C:\", "foo")
C:\foo
PS C:\> [System.IO.Path]::Combine("C:\", "foo", "bar")
Cannot find an overload for "Combine" and the argument count: "3".
At line:1 char:26
+ [System.IO.Path]::Combine <<<< ("C:\", "foo", "bar")
    + CategoryInfo          : NotSpecified: (:) [], MethodException
    + FullyQualifiedErrorId : MethodCountCouldNotFindBest

PS C:\> [System.IO.Path]::Combine(, "C:\", "foo", "bar")
Missing ')' in method call.
At line:1 char:27
+ [System.IO.Path]::Combine( <<<< , "C:\", "foo", "bar")
    + CategoryInfo          : ParserError: (CloseParenToken:TokenId) [], Paren
   tContainsErrorRecordException
    + FullyQualifiedErrorId : MissingEndParenthesisInMethodCall

PS C:\> [System.IO.Path]::Combine($("C:\", "foo", "bar"))
Cannot find an overload for "Combine" and the argument count: "1".
At line:1 char:26
+ [System.IO.Path]::Combine <<<< ($("C:\", "foo", "bar"))
    + CategoryInfo          : NotSpecified: (:) [], MethodException
    + FullyQualifiedErrorId : MethodCountCouldNotFindBest

this is what I do in c#, which works:

var foobar = Path.Combine(@"C:\", "foo", "bar");
Console.WriteLine(foobar);

What Powershell will invoke that specific overload? Path.Combine has both of these:

public static string Combine (string path1, string path2, string path3);
public static string Combine (params string[] paths);

Is it possible to call both of these, or just one? Obviously, in this specific case, it's difficult to tell the difference.

回答1:

The Path overloads that accept multiple arguments like that are only available in .NET 4 and up. You need to create a config file to tell Powershell to launch using .NET 4, which will give you access to those methods.

Create a file called "powershell.exe.config" in $pshome with the following contents:

<?xml version="1.0"?> 
<configuration> 
    <startup useLegacyV2RuntimeActivationPolicy="true"> 
        <supportedRuntime version="v4.0.30319"/> 
        <supportedRuntime version="v2.0.50727"/> 
    </startup> 
</configuration>

回答2:

To add, issuing the command:

[System.IO.Path]::Combine.OverloadDefinitions

from your shell, you should get the following output:

static string Combine(string path1, string path2)

As you can see, there are no overloads available.

Issue the command:

$PSVersionTable

and look at the CLRVersion - and you will see you are using a version of .net before 4.0, so there are no overloads for Path.Combine available.

回答3:

You need to create a params array in this case and call the Combine method on it.. The params array can be created as follows: @("C:\", "foo", "bar")

I believe event the following as a parameter "C:\,foo,bar" should call the second method.

I am not sure what you are confused about Path.Combine has two overloaded methods one is combinign two strings and the other a parameter array that accepts a bunch of arguments, the second case in powershell is handled differently than c#.

Hope this answers your question..

FYI, I am a powershell noob..