RGiesecke dll Export template

I have a need to create a dll that can be called from PowerBuilder 12.5. I found the RGiesecke.DllExport page at https://sites.google.com/site/robertgiesecke/Home/uploads#TOC-Samples. I created the following very simple c# project as a console app and in the wizard I selected dll:

VS2013 framework 3.5
Windows 7 

using System;
using System.Collections.Generic;
using System.Text;
using RGiesecke.DllExport;
using System.Runtime.InteropServices;

namespace PRS
{
   internal static class UnmanagedExports
   {
     [DllExport("getsmoochie", CallingConvention = CallingConvention.StdCall)]
     static string GetSmoochie()
     {
         return "Success";
     }
   }
}

I compile in Release mode as 32bit then attempt to access the dll from PowerBuilder with:

Function string GetSmoochie() library "PRS.dll"

I get back what looks like Chinese characters.

In addition I find one thing a little strange: if I try to register the dll with Regsvr32 I get and error telling me there is no dll entry point. I don't know what to think of that.

I have additional dll needs for PowerBuilder but I can't seem to get the simplest thing to work. Any help would be appreciated.

Thank you.

UPDATE:

It occurred to me that getting a mangled string back might not be a problem in this case since the code I really need to execute sends a file to a web service so I implemented the SendFile() code and it works from PowerBuilder.

One change I did make from the code above was to add the keyword "public" to the method call.

Summation: the RGiesecke dll Export template works!

UPDATE: See my note below. Here is my call with the filename passed in:

[DllExport("sendfile", CallingConvention = CallingConvention.StdCall)]
public static long SendFile(String filename)

Since the code with the file name hard-coded works I have to assume the file name is getting mangled somehow and the dll can't fin it.

Any ideas?

You have to marshal your return value too. This code works for me:

[DllExport("ExpTest", CallingConvention = CallingConvention.Winapi)]
[return: MarshalAs(UnmanagedType.LPWStr)]
public static string ExpTest([MarshalAs(UnmanagedType.LPWStr)] string sText, out int length)
{
    MessageBox.Show(sText);
    length=sText.Length;
    return sText;
}

PB 11.5 Classic
Target Framework .NET 4.5.2
Platform target x86