Create C# dll and use method with powershell

Question

I created a simple C# dll and registered it using RegAsm.exe. One very simple method is invoked without parameters and returns a number, here is a simplified version.

namespace AVL_test {
    interface ITestClass {
        int GetNumber();
    }

    [ComVisible(true)]
    public class TestClass: ITestClass {
        public TestClass() { }

        public int GetNumber() {
            return 10;
        }
    }
}

I need to invoke that method from Powershell, so I added the type

Add-Type -Path "C:\myPath\AVL_test.dll"

It seems to be loaded because if I [AVL_test.TestClass] I get this output

IsPublic IsSerial Name BaseType
-------- -------- ---- --------
True False TestClass System.Object

But if I try to invoke GetNumber() by typing[AVL_test.TestClass]::GetNumber() I get this error

Method invocation failed because [AVL_test.TestClass] does not contain a method named 'GetNumber'.

Am I doing something wrong?

Markus · Accepted Answer · 2015-05-07 09:34:13Z

11

Your method should be static or you need to create an instance of that type (TestClass).

Last can be done using

New-Object -TypeName <full qualified type name> -ArgumentList <args>

Or in your specific case:

$test = New-Object -TypeName AVL_Test.TestClass
$test.GetNumber()

answered May 7, 2015 at 9:34

Markus

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5 Comments

Naigel Over a year ago

Is there a way to implement a static method if I specify the interface? If I try to change method to public static int GetNumber() I get an error saying 'AVL_test.TestClass.GetNumber()' cannot implement an interface member because it is static

Markus Over a year ago

No, if there is an interface as in your example, than the method cannot be declared to be static ...

PeterK Over a year ago

On a related note, I don't think the [ComVisible] attribute is required for PowerShell interaction. You should only need this if you are registering the assembly as a COM object, but PowerShell will load .NET types and assemblies natively.

Markus Over a year ago

For the interaface question: You could add a static method, that is called by the interface method - just to provide both scenarios ...

Sam Tran Over a year ago

Nice. Is it possible to get the same return value using PowerShell Binary Module? Ie. one that contains/inherits from cmdlet classes.

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