Managed String to Unmanaged VARIANT

picazo

Hello, I have the following unmanaged method:

BSTR UnmanagedClass::UnmanagedMethod( BSTR x, VARIANT y, BSTR z )
{
...
}

I am wrapping that method with the following C++/CLI method:

String^ ManagedClass::ManagedMethod( String^ x, String^ y, String^ z )
{
   CComBSTR bstrX, bstrZ;
   bstrX.Attach( ( BSTR )( void * )Marshal::StringToBSTR( x ) );
   bstrZ.Attach( ( BSTR )( void * )Marshal::StringToBSTR( z ) );

   ????

   return gcnew String( unmanaged->UnmanagedMethod( bstrX, ???, bstrZ ) );
}

The C++/CLI wrapper method will be accessed from C# as follows:

string x="some value", y="another value", z="a third value";
managed.ManagedMethod( x, y, z );

The problem I am having is converting the managed string handle (String^ y) to an unmanaged VARIANT parameter. I would like to be able to solve this problem without having to modify the unmanaged C++ code. Does anyone have any suggestions or ideas on how to do this? Thanks in advance,

----------------- Genaro

led mike

picazo wrote:

Marshal::StringToBSTR

Returns an IntPtr. You can't just cast that to a BSTR you have to use a method like ToInt32().

led mike

Nish Nishant

led mike wrote:

You can't just cast that to a BSTR you have to use a method like ToInt32().

ToPointer would be a better method to use there.

Regards, Nish

Nish’s thoughts on MFC, C++/CLI and .NET (my blog)
Currently working on C++/CLI in Action for Manning Publications. (*Sample chapter available online*)

Nish Nishant

You could do a String^ -> BSTR -> VARIANT.

Regards, Nish

Nish’s thoughts on MFC, C++/CLI and .NET (my blog)
Currently working on C++/CLI in Action for Manning Publications. (*Sample chapter available online*)

picazo

could you provide some sample code of how to do this? I thought of doing that, but I couldn't get it to work. Thanks,

----------------- Genaro

Nish Nishant

picazo wrote:

could you provide some sample code of how to do this? I thought of doing that, but I couldn't get it to work.

Since you've already written code to convert String^ to BSTR, I presume your problem is with converting that to a VARIANT. To do that, you can use _variant_t which has a constructor that takes a BSTR, and use that. You can pass _variant_t anywhere a VARIANT is expected.

Regards, Nish

Nish’s thoughts on MFC, C++/CLI and .NET (my blog)
Currently working on C++/CLI in Action for Manning Publications. (*Sample chapter available online*)

led mike

Nishant Sivakumar wrote:

would be a better method to use

Sure but my level of apathy for people writing production code that can't blow their own nose is fairly high today. :-D I feel like starting a new CodeProject account with the user name "HellNo" for replying to all the "can you provide the code" lovelies. Or maybe I shoudl write a programming book titled "Copy Paste for Idiots"... wait...

Chapter One

Copy the following code and paste it into your code file at the appropriate location:

int n = 11;

Now modify the code until it produces the desired results.

There finished... now all I need is to send it off to a publisher.

led mike