Pass from cstring to system::string from C++ to C#

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void CMFCwithCSharpDlg::OnBnClickedBtnAdd()
{
	CSharp::CSharpMath^ mathClass = gcnew CSharp::CSharpMath();
	int result = mathClass->Add(2, 6);

	char buf[200];
	sprintf_s(buf, "result: %d", result);
	CStringA cstr1("Hello");

	CString str = theApp.m_lpCmdLine;
	std::wstring ws(str);
	std::string s;

	s.assign(ws.begin(), ws.end());
	//MessageBoxA(GetSafeHwnd(), buf, "Message", MB_OK);

	mathClass->PrintLabelAction();
}

What I have tried:

I tried to use string but in c++ there is std::string and in c# System::string, so I don't know how I can do

Posted 30-Nov-23 3:37am

Member 14594285

Updated 30-Nov-23 7:32am

Andre Oosthuizen

v2

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CPallini 30-Nov-23 9:51am

And... Where is the C# System::String?

Member 14594285 30-Nov-23 10:00am

In fact I dont know how I can pass to std::string to System string to pass variable to PrintLabelAction

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Andre Oosthuizen · Answer 1 · 2023-11-30T07:48:00

To convert a 'std::string' to a C# 'System::String' in C++, you can use 'msclr::interop::marshal_as' This header gives you utilities to use for converting between managed and native types, more on this here -
Managed C++ to C# Conversion [^]

C++

#include <msclr/marshal_cppstd.h>

//Using your std::string named 's' that you want to convert...
std::string s = "YourStandardStringHere";

//Convert your std::string to System::String...
System::String^ csString = msclr::interop::marshal_as<System::String^>(s);

Maxim Kartavenkov · Answer 2 · 2023-11-30T20:52:00

Solution 3

.NET string type constructor accepts the raw character array as an arguments.
So, along with marshal_as you can do it next way:

std::string std_string = "Some text";
String^ s = gcnew String(std_string.c_str());

Regards,
Maxim

Posted 30-Nov-23 20:52pm

Maxim Kartavenkov

Richard MacCutchan · Answer 3 · 2023-11-30T04:14:00

Solution 1

Since you are using C++/CLI then you should also use String Class (System) | Microsoft Learn[^].

Posted 30-Nov-23 4:14am

Richard MacCutchan

Comments

Member 14594285 30-Nov-23 10:17am

but I can use System only in c#..and for c++?

Richard MacCutchan 30-Nov-23 10:18am

You are using gcnew which is part of .NET, so you must have access to all its other features.

Member 14594285 30-Nov-23 10:22am

I have error if I write using System..I don't know why

Richard MacCutchan 30-Nov-23 10:43am

Sorry, but we cannot guess what you are doing, or what happens. You need to provide a proper detailed explanation of your problem.