Question

Edit: I found the relative page which is about C# and COM:How does the C# compiler detect COM types?

As in title, when I was converting a program in C# to IronPython, I couldn’t create instance of a class.

The original C# program:IAgilent34980A2 host = new Agilent34980A();

The rewritten IronPython program:host = Agilent34980A()

The C# program works well, while the IronPython program gets an error as:

TypeError: Cannot create instances of Agilent34980A because it is abstract

Actually Agilent34980A() is an interface, so the error is reasonable.

My question is why it works in C#? The instance is also can’t be created in C# which is an interface, right?

Addition:

The C# code is from test machine marker.

The IAgilent34980A2 definition part of source code is as following:

using Ivi.Driver.Interop;

using System;

using System.Runtime.InteropServices;

namespace Agilent.Agilent34980A.Interop

{

  //     IAgilent34980A interface.

[TypeLibType(256)]
[Guid("07678A7D-048A-42A6-8884-6CC8C575BD1F")]
[InterfaceType(1)]
public interface IAgilent34980A2 : IIviDriver
{
   IAgilent34980AMeasurement Measurement { get; }
   IAgilent34980AVoltage Voltage { get; }
  //  There are some similar functions following.
}

}

The Agilent34980A definition part

using System.Runtime.InteropServices;

namespace Agilent.Agilent34980A.Interop

{

  //     Agilent34980A driver class.
[Guid("07678A7D-048A-42A6-8884-6CC8C575BD1F")]
[CoClass(typeof(Agilent34980AClass))]
public interface Agilent34980A : IAgilent34980A2
{
}

}

And IIviDriver definition part

using System;

using System.Runtime.InteropServices;

namespace Ivi.Driver.Interop

{

//     IVI Driver root interface
[TypeLibType(256)]
[InterfaceType(1)]
[Guid("47ED5184-A398-11D4-BA58-000064657374")]
public interface IIviDriver
{
   //     Pointer to the IIviDriverOperation interface
   [DispId(1610678272)]
   IIviDriverOperation DriverOperation { get; }
   
   //     Pointer to the IIviDriverIdentity interface
   [DispId(1610678273)]
   IIviDriverIdentity Identity { get; }
   //  There are some similar functions following.
}

Answer 1

Actualy, you could create an interface instance through the co-class with both [CoClass] and [Guid] attributes.

That allow you to:

[Guid("000208D5-0000-0000-C000-000000000046")] // Anything
[CoClass(typeof(Foo))]
[ComImport]
public interface IFoo { void Bar(); }

public class Foo : IFoo { public void Bar() { return; } }

void Main()
{
    IFoo instance = new IFoo();
}