I don't think System::Exception contains enough type information about
unmanaged exceptions. You have to catch int as an unmanaged exception.

You should always catch unmanaged exceptions first, then managed ones,
like this:

try
{
   throw int(10);
   //throw std::exception("a"); // try this too
}
catch(std::exception& ex)
{
   Console::WriteLine("std::exception: " + gcnew String(ex.what()));
}
catch(int value)
{
   Console::WriteLine("int: " + value.ToString());
}
catch(Exception^ ex)
{
   Console::WriteLine("Exception^: " + ex->Message);
}

It doesn't matter if you catch int or std::exception first, but
Exception^ goes last. Also, the most derived type in the hierarchy goes
first:

try
{
}
catch(std::runtime_error& )
{
}
catch(std::exception& )
{
}

Tom