Pass Nothig value to Com component

I've builded a Net-Com Interop Library, wich I need to invoke from C++.
The library works sucessfully, but I need to pass COM VB Nothing in some arguments means the are not value for the argument.
Can any help me?
elbahariAsked:
Who is Participating?
 
Dariusz DziaraConnect With a Mentor ProgrammerCommented:
Maybe change (this is alternative)

FunctionCom()

so you will pass pointer instead of value like:

FunctionCom([in] long *pVal)

then you can call

FunctionCom(NULL)

to indicate NO VALUE

or add extra parameter

FunctionCom([in] long Val, [in] BOOL Empty)

to indicate such case

0
 
Jose ParrotGraphics ExpertCommented:
Hi,

Assuming the DLL can manage the absence of an explicit parameter, the call is made with NULL.
Exemples:
    MyFunction(param1, param2, NULL, param4, NULL);
    MyFunction(param1, param2, , param4,);

Jose
0
 
clockwatcherCommented:
See the following article:

  http://support.microsoft.com/kb/q238981/

Optional parameters are specified as:

      // VARIANT used in place of optional-parameters.
      VARIANT varOpt;
      varOpt.vt = VT_ERROR;
      varOpt.scode = DISP_E_PARAMNOTFOUND;
0
 
elbahariAuthor Commented:
I´ve increased the  value.....

I´ve an external library thant receive an string in C++, from an external source.
This string contains an integer value if the value change, or spaces if they are not changes.
I use c++ to retrieve the value, and I´ve builted a COM component in order to send the value to an NET app, receiving an integer value to the parameret. To do, I convert the string to an in

char NumericText[7]={"\0"};
memcpy(NumericText,response->externalLibrary.thisValue,6);
NumericValue=atoi(NumericText);
FunctionCom(NumericValue);

I want to send the numeric value if the string content has not spaces, or  "Nothing" if the string contains spaces.

Obviously, the solution is not call or not  or not the FunctionCom, because real FunctionCom has many others parameters and values wich I need to send.

Thanks a lot

 





 





0
 
elbahariAuthor Commented:
Ok, Thanks a lot, Mr Blue, both works sucessfully.
0
Question has a verified solution.

Are you are experiencing a similar issue? Get a personalized answer when you ask a related question.

Have a better answer? Share it in a comment.

All Courses

From novice to tech pro — start learning today.