How to use UTF8Encoding in Visual C ++

I need to change the C # code below to C ++ code.

    public static byte[] StrToByteArray(string str)
    {
        System.Text.UTF8Encoding encoding = new System.Text.UTF8Encoding();
        return encoding.GetBytes(str);
    }

on this site I found C ++ code for UTF8Encoding from which I created this code

    void StrToByteArray(string unicodeString)
    {
        UTF8Encoding^ utf8 = gcnew UTF8Encoding;
        array<Byte>^encodedBytes = utf8->GetBytes( unicodeString );
    }

but this gives me the following error:

Error 2 of error C2664: 'cli :: array ^ System :: Text :: Encoding :: GetBytes (cli :: array ^)': cannot convert parameter 1 from 'std :: string' to 'Cli :: array

Why do this while it is identical to the documentation? (except that I am using a normal string, but using a top-level string ^ gives me an error.)

I'm not sure if this is related, but my code is managed.

note: I didn’t worry about returning data until I got this working.