[英]Passing a C# string to C++/CLI does not show the string value in the CPP program
I want to call a C# function from C++ , via CLI/C++. 我想通过CLI / C ++从C ++调用C#函数。
C# code C#代码
private string _text = " ";
public void setText(string text)
{
// _text = text;
_text = "HI World";
}
Ideally setText shall have the commented line only. 理想情况下,setText应该仅包含注释行。 The _text = "HI World" is an example. _text =“ HI World”是一个示例。
public string getText()
{
return _text;
}
C++/CLI code C ++ / CLI代码
Header : 标头:
gcroot<Bridge> _managedObject;
virtual void setText(std::string text);
virtual std::string getText();
CPP file CPP文件
std::string CStringBridge::getText()
{
// _managedObject = gcnew Bridge(); // _managedObject = gcnew Bridge(); return (marshal_as(_managedObject->getText())); 返回(marshal_as(_managedObject-> getText())); } }
void CStringBridge::setText(std::string text)
{
// _managedObject = gcnew Bridge(); // _managedObject = gcnew Bridge(); _managedObject->setText(gcnew System::String(text.c_str())); _managedObject-> setText(gcnew System :: String(text.c_str())); } }
IStringBridgeWrapper* IStringBridgeWrapper::CreateInstance(void)
{
return ((IStringBridgeWrapper *)new CStringBridge());
}
Note : When I use the following code 注意:当我使用以下代码时
virtual void setText(System::String^ text);
virtual System::String^ getText();
I get the following error 3395 我收到以下错误3395
*__declspec(dllexport) cannot be applied to a function with the __clrcall calling convention* * __ declspec(dllexport)不能应用于具有__clrcall调用约定的函数*
, and so I stuck to std::string ,所以我坚持使用std :: string
When I use the library from the C++/CLI code, and call from my C++ program, "Hi World" should be printed ; 当我使用C ++ / CLI代码中的库并从我的C ++程序中调用时,应打印“ Hi World”; instead nothing gets printed 相反,什么都没有打印
C++ console application C ++控制台应用程序
IStringBridgeWrapper *pBridge = IStringBridgeWrapper::CreateInstance();
pBridge->setText(std::string("I am here"));
pBridge->getText();
I think the string is not being properly passed . 我认为该字符串未正确传递。
Any ideas to solve it shall be appreciated. 任何解决它的想法将不胜感激。
EDIT 编辑
I have updated the code after the comments , yet nothing shows up. 我已经在注释后更新了代码,但是什么也没有显示。
gcroot creates a handle, but does not allocate memory for it. gcroot创建一个句柄,但不为其分配内存。 But as Bridge has no memory allocated , the application does not work.My code is in the same lines at the article here - http://www.codeproject.com/Articles/10020/Using-managed-code-in-an-unmanaged-application . 但是由于Bridge没有分配内存,因此该应用程序无法正常工作。我的代码在本文的同一行中-http: //www.codeproject.com/Articles/10020/Using-managed-code-in-an-非托管应用程序 。
I want to call a C# function from C++ , via CLI/C++. 我想通过CLI / C ++从C ++调用C#函数。
Wait... you want to call a C++ function from C#, right? 等待...您想从C#调用C ++函数,对吧? That's what C++/CLI is good for. 这就是C ++ / CLI的优点。 Wrapping C++ code to be accessible in managed environments. 包装C ++代码以在托管环境中访问。 If you really want to call C# code from C++, you should look into COM registering your C# code. 如果您真的想从C ++调用C#代码,则应考虑使用COM注册您的C#代码。 If you use C++/CLI for this, your whole C++ program will be dragged into the .NET world and you could have used C# from the start. 如果为此使用C ++ / CLI,则整个C ++程序将被拖入.NET世界,并且您可能从一开始就使用C#。
In C++/CLI, your whole public class interface of ref (.NET) classes should consist of only managed types. 在C ++ / CLI中,您的ref(.NET)类的整个公共类接口应仅由托管类型组成。 That would be System::String^
instead of std::string
. 那应该是System::String^
而不是std::string
。
COM is your friend: COM是您的朋友:
Create a an interface in C# 在C#中创建接口
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Runtime.InteropServices;
namespace CsharpLibrary
{
// Since the .NET Framework interface and coclass have to behave as
// COM objects, we have to give them guids.
[Guid("56A868B1-0AD4-11CE-B03A-0020AF0BA770"),
InterfaceType(ComInterfaceType.InterfaceIsDual)]
public interface IStringHolder
{
String GetText();
void SetText(String s);
}
}
Implement the C# interface: 实现C#接口:
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Runtime.InteropServices;
namespace CsharpLibrary
{
[Guid("C6659361-1625-4746-931C-36014B146679")]
public class MyStringHolder : IStringHolder
{
String _text;
public String GetText()
{
return this._text;
}
public void SetText(String value)
{
_text = value;
}
}
}
Create and call your C# object from C++ 从C ++创建并调用C#对象
#include <windows.h>
#include <stdio.h>
#pragma warning (disable: 4278)
// To use managed-code servers like the C# server,
// we have to import the common language runtime:
#import <mscorlib.tlb> raw_interfaces_only
#pragma warning (disable: 4278)
// To use managed-code servers like the C# server,
// we have to import the common language runtime:
#import <mscorlib.tlb> raw_interfaces_only
#import "..\CsharpLibrary\bin\Debug\CsharpLibrary.tlb" no_namespace named_guids
int main(int argc, char* argv[])
{
HRESULT hr = S_OK;
IStringHolder *pStringHolder = NULL;
//
// Initialize COM and create an instance of the InterfaceImplementation class:
//
CoInitialize(NULL);
hr = CoCreateInstance( __uuidof(MyStringHolder),
NULL,
CLSCTX_INPROC_SERVER,
__uuidof(IStringHolder),
reinterpret_cast<void**>(&pStringHolder));
if(SUCCEEDED(hr))
{
_bstr_t sHelloWorld = SysAllocString( L"Hello, World" );
hr = pStringHolder->SetText(sHelloWorld);
SysFreeString(sHelloWorld);
}
//
// Be a good citizen and clean up COM
//
CoUninitialize();
return hr;
}
On the C# side you have to generate the type library and register the class by a post-build event: 在C#端,您必须生成类型库并通过构建后事件注册类:
generate the type library: "$(FrameworkSDKDir)bin\\NETFX 4.0 Tools\\tlbexp.exe" "$(TargetPath)" /out:"$(TargetDir)$(TargetName).tlb" 生成类型库:“ $(FrameworkSDKDir)bin \\ NETFX 4.0 Tools \\ tlbexp.exe”“ $(TargetPath)” /out:"$(TargetDir)$(TargetName).tlb“
register the class: C:\\Windows\\Microsoft.NET\\Framework\\v4.0.30319\\RegAsm.exe "$(TargetPath)" 注册该类:C:\\ Windows \\ Microsoft.NET \\ Framework \\ v4.0.30319 \\ RegAsm.exe“ $(TargetPath)”
Enjoy! 请享用!
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