Invalid Procedure call or argument in VB Client ?

[viral_umang hotmail com]

Hi all! I am writing COM Server.I am using User defined data type a Student structure in COM Server. There is a method in COM Server that returns the 1 st ranked student out of the student array passed to it from vb client. The Interface method is like this. STDMETHODIMP CStudentUtil::GetFirstRankStudent(SAFEARRAY **StudentArray,Student *pStudent) { if(!StudentArray) return(E_POINTER); if(!pStudent) return(E_INVALIDARG); long lBound=-1; long UBound=-1; Student *ob1=NULL,*ob2=NULL,*max=NULL; HRESULT hr; hr=::SafeArrayGetUBound(*StudentArray,1,&UBound); hr=::SafeArrayGetLBound(*StudentArray,1,&lBound); hr=::SafeArrayGetElement(*StudentArray,&lBound,(void*)ob1); max=ob1; if(FAILED(hr)) return hr; for(long i=lBound+1;iTotal>ob1->Total)/*Total is the member of my Student structure*/ max=ob2; } } pStudent=max; return S_OK; } The client side is Dim d As STUDENTLib.Student Set ob = New STUDENTLib.StudentUtil d = ob.GetFirstRankStudent(a) Set ob = Nothing What is wrong with the code in the client side that result in Invalid Procedure call or argument. Pls help on this. Thanks in advance. Viral Joshi.

[Lim Bio Liong]

Hello Joshi, I ran through your example and discovered one -possible- point of the E_INVALIDARG error occurs at the following line of code : hr=::SafeArrayGetElement(*StudentArray,&i,(void*)ob2); I declared the GetFirstRankStudent() method as follows : HRESULT GetFirstRankStudent([in] SAFEARRAY(Student)* pStudentArray, [out, retval] Student* pStudent); The SafeArrayGetElement() API makes a COPY of the required element of the array and so you must pass a pointer to an actual Student struct object (memory allocated for it already). Your code above sends a NULL pointer as the 3rd parameter (i.e. ob2). This is the reason for the E_INVALIDARG error. As a suggestion, I changed your code to as follows : //Student *ob1=NULL,*ob2=NULL,*max=NULL; Student ob2,*max=NULL; Student ob1; ... hr=::SafeArrayGetElement(*StudentArray,&lBound,(void*)&ob1); max=&ob1; if(FAILED(hr)) // this was where the original E_INVALIDARG appeared. return hr; for(long i=lBound+1;i < UBound; i++) { hr=::SafeArrayGetElement(*StudentArray,&i,(void*)&ob2); if(FAILED(hr)) return hr; else { if(ob2.Total>ob1.Total) max=&ob2; } } memcpy (pStudent, max, sizeof(Student)); return S_OK; Best Regards, Bio.

[viral_umang hotmail com]

Thanks for the kind co-operation. I've also found the same error. Now the code is working fine. Once again thanks for your efforts. Viral Joshi

[Lim Bio Liong]

Most welcome, Joshi. - Bio.