Conversion Array to Variant?

Thread view:

Enable EMail Alerts

Start New Thread

Thread rating:

Sebastian W - 04 Oct 2005 13:51 GMT

Hello.
I need to pass a String-Array as a COM-VARIANT.
In VB6 ist very easy:
dim s(0 to 9) as string
dim x as variant
x=s

But in .net I can not get it working.
I tried using Marshal.GetNativeVariantForObject but it needs a IntPtr
to store the variant in.
How do I create/allocate/reserve this IntPtr??

Marshal.AllocCoTaskMem needs a size and Marshal.SizeOf does not accept
arrays :-(

Can anybody help me?

Thanks in advance
Sebastian

Reply to this Message

Mattias Sjögren - 04 Oct 2005 15:58 GMT

>I need to pass a String-Array as a COM-VARIANT.

Can't you just pass it in directly?

>I tried using Marshal.GetNativeVariantForObject but it needs a IntPtr
>to store the variant in.
>How do I create/allocate/reserve this IntPtr??
>
>Marshal.AllocCoTaskMem needs a size and Marshal.SizeOf does not accept
>arrays :-(

Well the size of a VARIANT is always 16 bytes on Win32, so
AllocCoTaskMem(16) should work.

Mattias

Signature

Mattias Sjögren [MVP] mattias @ mvps.org
http://www.msjogren.net/dotnet/ | http://www.dotnetinterop.com
Please reply only to the newsgroup.

Reply to this Message

Sebastian W - 05 Oct 2005 10:17 GMT

Hello. It does not work.
I allocated a IntPtr and could do a GetNativeVariantForObject, but when
I pass it to the COM-Method it says "COM Exception: Type Mismatch".
Same when I just pass it directly.

The Methods's parameter is declared as VARIANT* data

Any idea?
Sebastian

Reply to this Message

Egbert Nierop (MVP for IIS) - 06 Oct 2005 08:04 GMT

> Hello. It does not work.
> I allocated a IntPtr and could do a GetNativeVariantForObject, but when
[quoted text clipped - 4 lines]
>
> Any idea?

Hi Sebastian,

Often you don't need to 'hack' arrays yourselves, in fact, you seldom would
need to. Sample

So if your method is PInvoked this would be good enough
[DllImport("myDLL.dll",

CharSet=CharSet.Unicode,

EntryPoint="yourmethod",

SetLastError=false, ExactSpelling=true)]

public static extern int Blah(ref object yourvariant); <- note the ref!
since your method is VARIANT*

[DllImport("myDLL.dll",

CharSet=CharSet.Unicode,

EntryPoint="GenerateLicense",

SetLastError=false, ExactSpelling=true)]

public static extern int Blah(

[MarshalAs(UnmanagedType.BStr)] string domain,

[MarshalAs(UnmanagedType.SafeArray, SafeArraySubType=VarEnum.VT_BSTR)]
string[] serversList,

[MarshalAs(UnmanagedType.BStr)] ref string theBstr);

In ATL the declaration is as follows (the in/out comments were added for
readability)
STDMETHODIMP Blah(/*in*/ BSTR domain,

/*in*/ SAFEARRAY* serversList,

/*in,out*/ BSTR * theBstr);

if serversList were a VARIANT array, just make the VarEnum.VT_VARIANT or
just leave out the whole declaration since object[] serverList would be
implicitely compiled by the compiler that way.

Reply to this Message

Sebastian W - 06 Oct 2005 09:45 GMT

Hi Thanks for the answer.

The problem is - this method is part of Class of a ActiveX-Control. The
IDE has created the two Wrappers (AxBlah and InteropBlah) for the
Component.
Therefore I cannot use the DLLImport Statement, right?
What can I do?
Is it possible to write this into the IL Code of the wrapper libarys?

Sebastian

Reply to this Message

Conversion Array to Variant?

Free Magazines