c++ - COM object that has been separated from its underlying RCW cannot be used

Question

My problem is the error message in the title:

COM object that has been separated from its underlying RCW cannot be used.

I have tried to google it, but i could find only solutions related to destructors/releasing objects. It is not something i want to do.

First, here is my code:

String^ filename="c:\\wb.xlsx";
Microsoft::Office::Interop::Excel::Application^ exApp= gcnew Microsoft::Office::Interop::Excel::ApplicationClass();
exApp->Visible=false;
exApp->Workbooks->Open(filename, 2, true, Type::Missing, Type::Missing, Type::Missing, true, Type::Missing, Type::Missing, Type::Missing, Type::Missing, Type::Missing, Type::Missing, Type::Missing, Type::Missing);
Worksheet^  exWss;
for (int x = 0; x <= checkedListBox1->CheckedItems->Count - 1; x++){
    for (int p=0; p<checkedListBox1->Items->Count; p++){
        if (checkedListBox1->CheckedItems[x]->ToString()->Equals(checkedListBox1->Items[p]->ToString())){
            p++;
            exWss  = safe_cast<Worksheet^> (exApp->ActiveWorkbook->Sheets[p]);
        }
    }
}

In short: i have a checkedlistbox, this part of code is ran when the necessary stuff have been selected. In the checkedlistbox the different sheets of the Excel workbook are listed. I am trying to select the sheet from the workbook according to the selected item in the checkedlistbox.

At the last code line (exWss = safe_cast (exApp->ActiveWorkbook->Sheets[p]);) I get the mentioned error message.

I have seen that Marshal releasing can cause such problems. In another function although i run Marshal.Releasecomobject, but it is completely separated, and i get the same error without it also.

Any ideas would be appreciated.

Answer 1

It seems for some reason the 'for' block separates completely the Interop object from the rest of the code. I managed to solve the problem by initializing the Interop object within the 'for' block. (I have introduced a bool variable, indicating if the workbook has been opened already - if it is false, it opens it within the 'for' block - otherwise it continues)

Interestingly however the object is accessible out of the 'for' block without a problem. I am sure there is an explanation for that, that i do not know - I am newbie, hobby programmer only.