How to set file properties for Excel file in C++.NET

/*------------------------------------------------------------------------------
 | Tutorial 33
 |
 | This tutorial shows how to set document properties for Excel file in C++.NET,
 | like 'Subject' property for summary information, 'Manager' property for
 | document summary information and a custom property.
 -------------------------------------------------------------------------------*/

using namespace System;
using namespace EasyXLS;
using namespace EasyXLS::Constants;

int main()
{
    Console::WriteLine("Tutorial 33\n----------\n");

    // Create an instance of the class that exports Excel files
    ExcelDocument ^workbook = gcnew ExcelDocument(1);

    // Set the 'Subject' document property
    workbook->getSummaryInformation()->setSubject("This is the subject");

    // Set the 'Manager' document property
    workbook->getDocumentSummaryInformation()->setManager("This is the manager");

    // Set a custom document property
    workbook->getDocumentSummaryInformation()->setCustomProperty("PropertyName", FileProperty::VT_NUMBER, "4");

    // Export Excel file
    Console::WriteLine("Writing file C:\\Samples\\Tutorial33 - Excel file properties.xlsx.");
    workbook->easy_WriteXLSXFile("C:\\Samples\\Tutorial33 - Excel file properties.xlsx");

    // Confirm export of Excel file
    String ^sError = workbook->easy_getError();
    if (sError->Equals(""))
        Console::Write("\nFile successfully created. Press Enter to Exit...");
    else
        Console::Write(String::Concat("\nError encountered: ", sError, "\nPress Enter to Exit..."));

    // Dispose memory
    delete workbook;

    Console::ReadLine();

    return 0;
}