Reference Casting question.

peterdrozd

Hello I am having real trouble with the following code.

System::Boolean vDataEvent16::IsSet::get()
{
System::Boolean data = (System::Boolean)(((* _Event) & 0x01) != false);
return data;
}

I get an invalid cast exception. How would I overcome this? :omg: _Event is defined as a System::UInt16 ^ _Event and is passed in from C# assembly to the class constructor. I wanted to use unions with some structs to view bits in the struct as individual properties but I could not cast the System::UInt16 to an unsigned short or rather to an unmanaged value type either. Any suggesions Really appreciate the response. thanks -Peter

led mike

peterdrozd wrote:

I get an invalid cast exception.

In VS2008 I cannot reproduce the exception

led mike

Mark Salsbery

peterdrozd wrote:

!= false

You're comparing a UInt16 with false. That should be != 0

System::Boolean vDataEvent16::IsSet::get()
{
return (((*_Event) & 0x01) != 0);
}

Mark Salsbery Microsoft MVP - Visual C++ :java:

led mike

Did you reproduce the exception? Using what version of C++?

led mike

Mark Salsbery

led mike wrote:

Did you reproduce the exception?

No sir (VS 2008 SP1). I don't know what's up with that - not enough info for me. :)

Mark Salsbery Microsoft MVP - Visual C++ :java:

peterdrozd

I tried it and it does not work. It may be that I separated the class to a header file from the implemenation.

System::Boolean DataEvent16::IsActive::get()
{
System::Boolean data = (System::Boolean)(((* _Event) & 0x02) != 0); <--fails here.
return data;
}

header file
property System::Boolean IsActive
{
System::Boolean get();
}

this still fails. I am trying to get bits from an unsigned short and pass back to C# the value of the bits. I tried a union with a structure to define the bits and tried to set a variable that had all the bits as a System::UInt16 but it would not let me assign the * (System::Uint16 ^ ) to the unmanaged data type so I had to switch gears and try this method. doing a return when the class is implemented inline works fine however I can not use the class in another CPP file as a class variable because I could not make one class aware of the other with out a header. so I separated them. this led to problems with visual studio 2005 C++ CLI This should be a simple item but it's starting to take up so much time. :sigh: thanks -- Pete :)

modified on Thursday, September 11, 2008 11:34 AM

led mike

Mark Salsbery wrote:

I don't know what's up with that - not enough info for me.

Yeah I know, I plugged this in and ran it just fine

System::Boolean data = (System::Boolean)(((* _Event) & 0x01) != false);

led mike

Mark Salsbery · modified on Thursday, September 11, 2008 11:34 AM

led mike and I can't reproduce the error. Here's how I tested:

UInt16 ^_Event = gcnew UInt16(4);
Boolean boolean = (((*_Event) & 0x01) != false);

You don't need the (System::Boolean) cast. The != operator already returns a boolean. The only thing I can think of based on the code you've shown is _Event isn't really a UInt16 ^. Mark

Mark Salsbery Microsoft MVP - Visual C++ :java:

Mark Salsbery

I did this:

UInt16 ^ _Event = gcnew UInt16(4);
Boolean boolean = (((*_Event) & 0x01) != false);

*shrug*

Mark Salsbery Microsoft MVP - Visual C++ :java:

peterdrozd

here is part of the header file.

public ref class DataEvent16
{
private:
System::UInt16 ^ _Event;

public:
    DataEvent16(System::UInt16 ^ Event);
    DataEvent16();
    property System::UInt16 RawData
    {
        System::UInt16 get();
        void set ( System::UInt16 value);
    }
    property System::UInt16 IsSet
    {
        System::UInt16  get();
    }
    property System::Boolean IsActive
    {
        System::Boolean get();
    }

};

Implementation file

DataEvent16::vDataEvent16(System::UInt16 ^ Event)
{
_Event = Event;
}
DataEvent16::vDataEvent16()
{
_Event = gcnew System::UInt16(0);
}
System::Boolean vDataEvent16::IsActive::get()
{
System::Boolean data = (System::Boolean)(((* _Event) & 0x02) != 0);
return data;
}

this will compile but explode. on the boolean statement. I know it seems like overkill but I have tried several iterations. :)

led mike

Mark Salsbery wrote:

I did this:

and it didn't throw any exception right?

led mike

Mark Salsbery · modified on Thursday, September 11, 2008 11:34 AM

Are you sure the C# side is providing a System::Uint16 ^ and not just a System::Uint16? A System::Uint16 ^ (reference to a value type) is kind of unconventional...

Mark Salsbery Microsoft MVP - Visual C++ :java:

Mark Salsbery

I had to remove the 'v's (vDataEvent16, vDataEvent16) to get your code to compile, but it worked fine in VS 2008. Mark

Mark Salsbery Microsoft MVP - Visual C++ :java:

Mark Salsbery

Correctamundo!

Mark Salsbery Microsoft MVP - Visual C++ :java:

Mark Salsbery

BTW thanks for providing code to test with :) What does the calling code look like?

Mark Salsbery Microsoft MVP - Visual C++ :java:

peterdrozd

fixed it. I had to remove all references for that data. The problem was that I have some arguments that have to be passed as references. I have others that have to be passed as value types. the _Event is a value type. I was passing it in as a reference so in that function, I was referencing the pointer I think. So it would compile but the value was probably greater than max value. I guess this all came about because I have become accustomed to coding inline classes and not removing the class definition from the implementation. there are not too many good examples online that I found on how to do it right. thanks everyone for your help. -Peter :cool:

Mark Salsbery

That's what I figured - I just wasn't sure why the C# side didn't complain about a mismatched argument. :) Cheers, Mark

Mark Salsbery Microsoft MVP - Visual C++ :java: