C# SendMessage with WM_COPYDATA

[xMetalDetectorx]

I have two C# Applications. The first application has to send 2 strings to the other application. The first string is just a simple string "abc", while the 2nd string contains a path (Application.St artupPath). This is the code I use to send the data:

        //Used for WM_COPYDATA for string messages
        public struct COPYDATASTRUCT
        {
            public IntPtr dwData;
            public int cbData;
            [MarshalAs(UnmanagedType.LPStr)]
            public string jobName;
            [MarshalAs(UnmanagedType.LPStr)]
            public string path;
        }

        public int sendWindowsStringMessage(int hWnd, int wParam, string msg)
        {
            int result = 0;

            if (hWnd > 0)
            {
                byte[] sarr = System.Text.Encoding.Default.GetBytes(msg);
                int len = sarr.Length;
                COPYDATASTRUCT cds = new COPYDATASTRUCT();
                cds.dwData = (IntPtr)100;
                cds.jobName = msg; //first string
                cds.path = Application.StartupPath; //path string
                cds.cbData = len + 1;
                result = SendMessage(hWnd, WM_COPYDATA, wParam, ref cds);
            }

            return result;
        }

And this is how I listen for it:

        //Receives Windows Messages
        protected override void WndProc(ref Message message)
        {
            if (message.Msg == WM_COPYDATA)
            {
                COPYDATASTRUCT mystr = new COPYDATASTRUCT();
                Type mytype = mystr.GetType();
                mystr = (COPYDATASTRUCT)message.GetLParam(mytype);

                //see what path is being passed.
                MessageBox.Show(mystr.path);

                //Process
                Process(mystr.jobName);

                
            }
            //be sure to pass along all messages to the base also
            base.WndProc(ref message);
        }

The first string (jobName) is received fine, but the second string (path) comes up as a bunch of garbage characters. The path on the sending side is sent as "C:\\Path\\Dir" , on the receiving side i get "¸`dã"

Any idea why path strings aren't being sent correctly?

[Plater]

instead of using string Path (etc) try doing it with a StringBuilder ?
I have seen people have luck using a stringbuilder through marshalling vs strings