convert from std::string to String^

Question

I have a function in C++ that have a value in std::string type and would like to convert it to String^.

void(String ^outValue)
{
   std::string str("Hello World");
   outValue = str;
}

I think you need another tag because String^ doesn't make much sense in C++. — juanchopanza
– juanchopanza, Commented Dec 5, 2012 at 7:21
This is managed c++ syntax. And your function isn't even valid, there is no identifier. — Aesthete
– Aesthete, Commented Dec 5, 2012 at 7:24
The problem is that this function is used to convert a value from C++ to C#/ I mean this function is called by C# program — Moti
– Moti, Commented Dec 5, 2012 at 7:24
@juanchopanza it also exists in WinRT, and probably should call .c_str(); on the std::string — johnathan
– johnathan, Commented Dec 5, 2012 at 7:24

Teodor Ciuraru · Accepted Answer · 2015-01-02 11:29:11Z

15

From MSDN:

#include <string>
#include <iostream>
using namespace System;
using namespace std;

int main() {
   string str = "test";
   String^ newSystemString = gcnew String(str.c_str());
}

http://msdn.microsoft.com/en-us/library/ms235219.aspx

answered Jan 2, 2015 at 11:29

Teodor Ciuraru

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Mark Tolonen · Accepted Answer · 2012-12-05 07:41:04Z

11

Googling reveals marshal_as (untested):

// marshal_as_test.cpp
// compile with: /clr
#include <stdlib.h>
#include <string>
#include <msclr\marshal_cppstd.h>

using namespace System;
using namespace msclr::interop;

int main() {
   std::string message = "Test String to Marshal";
   String^ result;
   result = marshal_as<String^>( message );
   return 0;
}

Also see Overview of Marshaling.

edited Dec 5, 2012 at 7:41

answered Dec 5, 2012 at 7:35

Mark Tolonen

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1 Comment

DKS Over a year ago

This no longer compiles.

Florian Straub · Accepted Answer · 2021-01-19 16:24:54Z

2

As far as I got it, at least the marshal_as approach (not sure about gcnew String) will lead to non ASCII UTF-8 characters in the std::string to be broken.

Based on what I've found on https://bytes.com/topic/c-sharp/answers/725734-utf-8-std-string-system-string I've build this solution which seems to work for me at least with German diacritics:

System::String^ StdStringToUTF16(std::string s)
{

 cli::array<System::Byte>^ a = gcnew cli::array<System::Byte>(s.length());
 int i = s.length();
 while (i-- > 0)
 {
    a[i] = s[i];
 }

 return System::Text::Encoding::UTF8->GetString(a);
}

answered Jan 19, 2021 at 16:24

Florian Straub

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