Question

Firstly here is the code that im trying to get to work-

private: System::Void openToolStripMenuItem_Click(System::Object^  sender, System::EventArgs^  e) {
         OpenFileDialog^ dlg = gcnew OpenFileDialog();
         dlg->Filter = "Text Files|*.txt";
         String^ stream;
         if(dlg->ShowDialog()==Windows::Forms::DialogResult::OK)
         {
            txtOutput->Text = System::IO::File::ReadAllText(dlg->FileName);


            char* num = (char*)(void*)Marshal::StringToHGlobalAnsi(stream); //Convert string to array of char

            for (int i=0;i<stream->Length;++i) //ERRONEOUS LINE!!
            {
                num[i] = num[i] ^ key;   //DECRYPT
            }
            String^ orig_stream = gcnew String(num);
            txtOutput->Text = orig_stream;

         }
     }

Im trying to Open a File which is already encrypted. The program compiles w/o any errors, but during runtime it gives me the following error with the options to break, continue or abort:

An unhandled exception of type 'System.NullReferenceException' occurred in Project_Targaryen.exe
Additional information: Object reference not set to an instance of an object.

The error points to the for loop line.
Any help is appreciated!

Answer 1

stream is not associated with an object before it is used in the for loop.