从具有非托管导出的C＃DLL中返回一个字符串到Inno安装脚本 [英] Returning a string from a C# DLL with Unmanaged Exports to Inno Setup script

问题描述

我有一个C＃DLL，它使用非管理导出由Inno Setup Pascal脚本直接调用。此函数需要返回一个字符串到Inno Setup。我的问题是如何完成这个？

我的首选方法是将缓冲区从Inno安装程序传递到C＃函数，该函数将返回此缓冲区内的字符串。我想出了这个代码：

I have a C# DLL which exposes a function using Unmanaged Exports which is called directly by an Inno Setup Pascal script. This function needs to return a string to Inno Setup. My question is how can I accomplish this?
My preferred method is to pass a buffer from Inno Setup to the C# function which will return the string inside this buffer. I've come up with this code:

C＃函数：

[DllExport("Test", CallingConvention = CallingConvention.StdCall)]
static int Test([Out, MarshalAs(UnmanagedType.LPWStr)] out string strout)
{
   strout = "teststr";
   return strout.Length;
}

Inno安装脚本：

function Test(var res: String):Integer; external 'Test@files:testdll.dll stdcall';

procedure test1; 
var
    Res: String;
    l: Integer;
begin
    SetLength(Res,256);
    l := Test(Res);
    { Uncommenting the following line causes an exception }
    { SetLength(Res,l); }
    Log('"Res"');
end;

当我运行此代码时， Res 变量是空的（我在日志中看到）

When I run this code the Res variable is empty (I see "" in the log)

如何从这个DLL中返回一个字符串？

How can I return a string from this DLL?

请注意，我使用的是Unicode版本的Inno Setup。我也不想使用COM来调用此函数，也不需要在DLL中分配缓冲区并将其返回到Inno Setup。

Note that I am using the Unicode version of Inno Setup. I also don't want to use COM to call this function nor to allocate a buffer in the DLL and return it to Inno Setup.

推荐答案

我建议您使用 BSTR 类型，这是用于interop函数调用的数据类型。在C＃方面，您可以使用 UnmanagedType.BStr 类型来编组您的字符串，而在Inno安装方面，您将使用 WideString ，它兼容 类型。所以你的代码会改为这个（另见 非管理导出文档的编组样本 章节）：

I would suggest you to use the BSTR type, which is used to be a data type for interop function calls. On your C# side you'd marshall your string as the UnmanagedType.BStr type and on the Inno Setup side you'd use the WideString, which is compatible with the BSTR type. So your code would then change to this (see also the Marshalling sample chapter of the Unmanaged Exports docs):

[DllExport("Test", CallingConvention = CallingConvention.StdCall)]
static int Test([MarshalAs(UnmanagedType.BStr)] out string strout)
{
    strout = "teststr";
    return 0; // indicates success
}

而在Inno安装方面，使用 WideString 到：

And on the Inno Setup side with the use of WideString to this:

[Code]
function Test(out strout: WideString): Integer;
  external 'Test@files:testdll.dll stdcall';

procedure CallTest;
var
  retval: Integer;
  str: WideString;
begin
  retval := Test(str);
  { test retval for success }
  Log(str);
end;

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