如何将C＃中的char传递给C ++ DLL [英] How to pass char in C# to C++ DLL

问题描述

你好，早上好

i尝试将c＃中的参数传递给cpp代码

但这是我在我的cpp中得到的结果

格式错误

hi hello and morning
i try to pass a parameter in c# to cpp code
but this is the result i get in my cpp
the format is wrong

╕τ≡»qsαΦópdsΓ╞òí4ΘáΦTΦF`fsΦ

有人可以告诉我我的代码有什么问题吗

这就是我的工作



我尝试过：


$ c $ b in c＃code

can someone tell me what is wrong with my code
this is what i have done

What I have tried:

in c# code

[DllImport("C:\\Users\\user\\Desktop\\mysqlcppConnector\\Debug\\mysqlcppConnector.dll")]
        public static extern string passingChar(StringBuilder charToPass);

passingChar(new StringBuilder("pass me to cpp right now!"));

$ c $ b cpp代码：

in the cpp code:

// please ignore the return type val..
// cause this should return the data from database
// char to pass is the statement of sqlquerry
// this is just a sample code of it
__declspec(dllexport) string passing char(char* charToPass){
printf(charToPass);
return someVal;
}

除此之外

i也用我的c＃代码做了这个

besides this
i also did this in my c# code

[DllImport("C:\\Users\\user\\Desktop\\mysqlcppConnector\\Debug\\mysqlcppConnector.dll")]
        public static extern string passingChar([MarshalAs( UnmanagedType.LPStr )] charToPass);

passingChar("pass me to cpp right now!");

这仍然是相同的，我无法得到我的实际字符串尝试传递给mt cpp代码

this is still same and i can not get the actual string that i try to pass to mt cpp code

推荐答案

首先，正确装饰你的DLLImport：

First, decorate your DLLImport correctly:

[DllImport("C:\\Users\\user\\Desktop\\mysqlcppConnector\\Debug\\mysqlcppConnector.dll", CallingConvention = CallingConvention.Cdecl)]
public static extern string passingChar(StringBuilder charToPass);

然后记住C＃字符串不是以null结尾 - 所以除非你将字符串长度传递给C ++，否则你需要在结尾处手动添加一个空值，否则C ++代码将不知道有多少字符。一个简单的 printf 或类似的，期望null终止 char * 数据将在没有它的情况下超出缓冲区。

Then remember that C# strings aren't null terminated - so unless you pass the string length to C++, you need to manually add a null value at the end or the C++ code will have no idea how many characters there are. A simple printf or similar that expects null terminated char* data will overrun the buffer without it.

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