根据对我的帖子的回复，我创建了一个新示例，该示例使用字符串缓冲区来返回字符串，而不仅仅是返回 PAnsiChars。
Delphi DLL 源码：
library DelphiLibrary;
uses SysUtils;
// Compiled using Delphi 2007.
// NOTE: If your project doesn't have version information included, you may
// receive the error "The "ResolveManifestFiles" task failed unexpectedly"
// when compiling the C# application.
{$R *.res}
// A note on returing strings. I had originally written this so that the
// output string was just a PAnsiChar. But several people pointed out that
// since Delphi strings are reference-counted, this was a bad idea since the
// memory for the string could get overwritten before it was used.
//
// Because of this, I re-wrote the example so that you have to pass a buffer for
// the result strings. I saw some examples of how to do this, where they
// returned the actual string length also. This isn't necessary, because the
// string is null-terminated, and in fact the examples themselves never used the
// returned string length.
// Example function takes an input integer and input string, and returns
// inputInt + 1, and inputString + ' ' + IntToStr(outputInt). If successful,
// the return result is true, otherwise errorMsgBuffer contains the the
// exception message string.
function DelphiFunction(inputInt : integer;
inputString : PAnsiChar;
out outputInt : integer;
outputStringBufferSize : integer;
var outputStringBuffer : PAnsiChar;
errorMsgBufferSize : integer;
var errorMsgBuffer : PAnsiChar)
: WordBool; stdcall; export;
var s : string;
begin
outputInt := 0;
try
outputInt := inputInt + 1;
s := inputString + ' ' + IntToStr(outputInt);
StrLCopy(outputStringBuffer, PAnsiChar(s), outputStringBufferSize-1);
errorMsgBuffer[0] := #0;
Result := true;
except
on e : exception do
begin
StrLCopy(errorMsgBuffer, PAnsiChar(e.Message), errorMsgBufferSize-1);
Result := false;
end;
end;
end;
// I would have thought having "export" at the end of the function declartion
// (above) would have been enough to export the function, but I couldn't get it
// to work without this line also.
exports DelphiFunction;
begin
end.
C# Code:
using System;
using System.Runtime.InteropServices;
namespace CsharpApp
{
class Program
{
// I added DelphiLibrary.dll to my project (NOT in References, but
// "Add existing file"). In Properties for the dll, I set "BuildAction"
// to None, and "Copy to Output Directory" to "Copy always".
// Make sure your Delphi dll has version information included.
[DllImport("DelphiLibrary.dll",
CallingConvention = CallingConvention.StdCall,
CharSet = CharSet.Ansi)]
public static extern bool
DelphiFunction(int inputInt, string inputString,
out int outputInt,
int outputStringBufferSize, ref string outputStringBuffer,
int errorMsgBufferSize, ref string errorMsgBuffer);
static void Main(string[] args)
{
int inputInt = 1;
string inputString = "This is a test";
int outputInt;
const int stringBufferSize = 1024;
var outputStringBuffer = new String('\x00', stringBufferSize);
var errorMsgBuffer = new String('\x00', stringBufferSize);
if (!DelphiFunction(inputInt, inputString,
out outputInt,
stringBufferSize, ref outputStringBuffer,
stringBufferSize, ref errorMsgBuffer))
Console.WriteLine("Error = \"{0}\"", errorMsgBuffer);
else
Console.WriteLine("outputInt = {0}, outputString = \"{1}\"",
outputInt, outputStringBuffer);
Console.Write("Press Enter:");
Console.ReadLine();
}
}
}
这里还有一个额外的类，展示了如何动态加载 DLL（抱歉，代码太长了）：
using System;
using System.Runtime.InteropServices;
namespace CsharpApp
{
static class DynamicLinking
{
[DllImport("kernel32.dll", EntryPoint = "LoadLibrary")]
static extern int LoadLibrary([MarshalAs(UnmanagedType.LPStr)] string lpLibFileName);
[DllImport("kernel32.dll", EntryPoint = "GetProcAddress")]
static extern IntPtr GetProcAddress(int hModule, [MarshalAs(UnmanagedType.LPStr)] string lpProcName);
[DllImport("kernel32.dll", EntryPoint = "FreeLibrary")]
static extern bool FreeLibrary(int hModule);
[UnmanagedFunctionPointer(CallingConvention.StdCall, CharSet = CharSet.Ansi)]
delegate bool DelphiFunction(int inputInt, string inputString,
out int outputInt,
int outputStringBufferSize, ref string outputStringBuffer,
int errorMsgBufferSize, ref string errorMsgBuffer);
public static void CallDelphiFunction(int inputInt, string inputString,
out int outputInt, out string outputString)
{
const string dllName = "DelphiLib.dll";
const string functionName = "DelphiFunction";
int libHandle = LoadLibrary(dllName);
if (libHandle == 0)
throw new Exception(string.Format("Could not load library \"{0}\"", dllName));
try
{
var delphiFunctionAddress = GetProcAddress(libHandle, functionName);
if (delphiFunctionAddress == IntPtr.Zero)
throw new Exception(string.Format("Can't find function \"{0}\" in library \"{1}\"", functionName, dllName));
var delphiFunction = (DelphiFunction)Marshal.GetDelegateForFunctionPointer(delphiFunctionAddress, typeof(DelphiFunction));
const int stringBufferSize = 1024;
var outputStringBuffer = new String('\x00', stringBufferSize);
var errorMsgBuffer = new String('\x00', stringBufferSize);
if (!delphiFunction(inputInt, inputString, out outputInt,
stringBufferSize, ref outputStringBuffer,
stringBufferSize, ref errorMsgBuffer))
throw new Exception(errorMsgBuffer);
outputString = outputStringBuffer;
}
finally
{
FreeLibrary(libHandle);
}
}
}
}
-Dan
