How to Create DLL in C# and call in Delphi XE6 [duplicate]

Question

I created a DLL in VS2013 using File/New Project/Class Library. I then tried to load it dynamically in Delphi. But Delphiis returning NIL for procedure GetProcAddress.

My C# & Delphi code looks like what I have posted below. In the code GetProcAddress is returning NIL. Please advise if I am missing something.

C# Code

using System;
namespace TestDLL
{
    public class Class1
    {
        public static string EchoString(string eString)
        {
            return eString;
        }
    }
}

Delphi Code

 Type
    TEchoString = function (eString:string) : integer;stdcall;

  function TForm1.EchoString(eString:string):integer;
  begin
    dllHandle := LoadLibrary('TestDLL.dll') ;
    if dllHandle <> 0 then
    begin
      @EchoString := GetProcAddress(dllHandle, 'EchoString') ;
      if Assigned (EchoString) then
            EchoString(eString)  //call the function
      else
        result := 0;
      FreeLibrary(dllHandle) ;
    end
    else
    begin
      ShowMessage('dll not found ') ;
   end;
end;

Answer 1

A C# DLL is a managed assembly and does not export its functionality via classic PE exports. Your options:

1. Use C++/CLI mixed mode to wrap the C#. You can then export functions in unmanaged mode in the usual way.
2. Use Robert Giesecke's UnmanagedExports. This is perhaps more convenient than a C++/CLI wrapper.
3. Expose the managed functionality as a COM object.

Once you get as far as choosing one of these options you will have to deal with your misuse of the string data type. That's a private Delphi data type that is not valid for interop. For the simple example in the question PWideChar would suffice.