Passing arrays from VB6 to C# ActiveX

From: Eugene Khosid (eugenek_at_gweiss.com)
Date: 02/24/04 

Date: Tue, 24 Feb 2004 14:03:00 -0500

Hi all,

I ran into this problem and I don't really know which peace of software it
to blame. Anyway, all I'm trying to do is to pass an array of strings
(variable size) from a VB6 client to C# class that exposes an ActiveX
interface. I tried to do various things without much success

1. Do nothing - just declare a class in C# that has a public method that
takes an array of strings and register the class for interop.
If I DONT use ClassInterface(ClassInterfaceType.None), attribute in C# I
dont get the list of availbale member functions in VB but the code WORKS. My
guess is because it uses late binding here.
If I use ClassInterface(ClassInterfaceType.None), attribute in C# then I'm
getting the following error message "Function or interface marked as
restricted, or the function uses an Automation type not supported by VB"

2. Use [MarshalAs(UnmanagedType.SafeArray)] in the declaration in C# code.
The result is same as above.

3. Use [MarshalAs(UnmanagedType.SafeArray)] in the declaration in C# code.
The result is also rather strange. The method is dropped from the type
library and therefore is not available in VB. The type library file looks
like this

[
  odl,
  uuid(DC6ECF1D-1E43-46BD-AC2D-FBC3222BB938),
  version(1.0),
  dual,
  oleautomation,
    custom({0F21F359-AB84-41E8-9A78-36D110E6D2F9},
"com.gweiss.Portal.Class1")

]
interface IPriceFeedExActiveX : IDispatch {
    [id(0x60020000)]
    HRESULT m1([in] aa* value);
    [id(0x60020001)]
    HRESULT m2([in] aa* value);
    [id(0x60020002)]
    HRESULT m3([out, retval] VARIANT_BOOL* pRetVal);
    [id(0x60020003)]
    HRESULT m4([out, retval] BSTR* pRetVal);
    [id(0x60020004)]
    HRESULT m5(
                    [in] ISymbolId* p_sRic,
                    [in] SAFEARRAY(BSTR) p_aFieldNames,
                    [out, retval] VARIANT_BOOL* pRetVal);
    [id(0x60020006)]
    HRESULT m7(
                    [in] ISymbolId* p_sRic,
                    [out, retval] VARIANT_BOOL* pRetVal);
    [id(0x60020007)]
    HRESULT m8(
                    [in] ISymbolId* p_sRic,
                    [out, retval] VARIANT_BOOL* pRetVal);
};

Notice the missing entry of m6(...)

I'm really bothered by all these things. I use VS.NET 2003 and VB6 SP5.

Also, everything works fine when calling C# ActiveX from an Excel
spread***.

If anyone can explain these anomalies I'd like to hear it!!

Thanks,

Eugene