将Delphi字符串作为参数发送到DLL

library MyDLL;

uses
  SysUtils,
  Classes;

{$R *.res}

function MyFunction(const AString: string): string; stdcall;
begin
  Result := 'Hello, ' + AString;
end;

exports
  MyFunction;

begin
end.

unit MainForm;

interface

uses
  Windows, Messages, SysUtils, Variants, Classes, Graphics, Controls, Forms,
  Dialogs, StdCtrls;

type
  TMyFunction = function(const AString: string): string; stdcall;

  TForm1 = class(TForm)
    Button1: TButton;
    procedure Button1Click(Sender: TObject);
  private
    { Private declarations }
  public
    { Public declarations }
  end;

var
  Form1: TForm1;
  MyFunction: TMyFunction;

implementation

{$R *.dfm}

procedure TForm1.Button1Click(Sender: TObject);
var
  DLLHandle: THandle;
  MyFunctionPtr: Pointer;
  ResultString: string;
begin
  DLLHandle := LoadLibrary('MyDLL.dll');
  if DLLHandle <> 0 then
  begin
    try
      MyFunctionPtr := GetProcAddress(DLLHandle, 'MyFunction');
      if Assigned(MyFunctionPtr) then
      begin
        MyFunction := TMyFunction(MyFunctionPtr);
        ResultString := MyFunction('World');
        ShowMessage(ResultString);
      end
      else
        ShowMessage('Unable to find function in DLL');
    finally
      FreeLibrary(DLLHandle);
    end;
  end
  else
    ShowMessage('Unable to load DLL');
end;

end.