![\"\"](\"https:\/\/mariusbancila.ro\/blog\/wp-content\/uploads\/2019\/12\/vsinstallercppcli.png\")
<\/li>\n<\/ul>\nWhen you install this component you get two new project templates:<\/p>\n
- \n
- CLR Class Library (.NET Core)<\/li>\n
- CLR Empty Project (.NET Core)<\/li>\n<\/ul>\n
![\"\"](\"https:\/\/mariusbancila.ro\/blog\/wp-content\/uploads\/2019\/12\/vscppcli.png\")
<\/p>\nCreating a C++\/CLI component<\/h3>\n
To demonstrate how the whole thing works, let us create a CLR Class Library (.NET Core) project (that we will called CoreClassLib<\/em>). In this class library, we will create a C++\/CLI class called Display<\/tt> that contains a single method Print()<\/tt> that simply prints a message to the console.<\/p>\n
#pragma once\r\n\r\nnamespace CoreClassLib \r\n{\r\n\tref class Display\r\n\t{\r\n\tpublic:\r\n\t\tvoid Print(System::String^ message);\r\n\t};\r\n}<\/pre>\n#include \"Display.h\"\r\n\r\nnamespace CoreClassLib\r\n{\r\n void Display::Print(System::String^ message)\r\n {\r\n System::Console::WriteLine(message);\r\n }\r\n}<\/pre>\nThen, we will create a C++ class, called Widget<\/tt> that has a single method called WriteText()<\/tt> that is supposed to print the message (to the console). To do so, it uses an instance of the Display<\/tt> class. The Widget<\/tt> is exported from the project, so it can be consumed from other modules. In order to be able to compile it, the mixed-managed components must not be part of the declaration of the Widget<\/tt> class. For this purpose, we use the PIMPL idiom below.<\/p>\n
#pragma once\r\n#include <string>\r\n\r\n#ifdef DLL_EXPORT\r\n#define DLL_API __declspec(dllexport)\r\n#else\r\n#define DLL_API __declspec(dllimport)\r\n#endif\r\n\r\nclass WidgetImpl;\r\n\r\nclass DLL_API Widget\r\n{\r\n WidgetImpl* impl; \r\n\r\npublic:\r\n Widget();\r\n ~Widget();\r\n\r\n void WriteText(std::string const& message);\r\n};<\/pre>\n#include \"Widget.h\"\r\n#include \"Display.h\"\r\n#include <vcclr.h>\r\n\r\nclass WidgetImpl\r\n{\r\n gcroot<CoreClassLib::Display^> display;\r\npublic:\r\n WidgetImpl()\r\n :display(gcnew CoreClassLib::Display())\r\n {\r\n }\r\n\r\n void WriteText(std::string const& message)\r\n {\r\n display->Print(gcnew System::String(message.c_str()));\r\n }\r\n};\r\n\r\nWidget::Widget()\r\n :impl(new WidgetImpl())\r\n{\r\n}\r\n\r\nWidget::~Widget()\r\n{\r\n delete impl;\r\n}\r\n\r\nvoid Widget::WriteText(std::string const& message)\r\n{\r\n impl->WriteText(message);\r\n}<\/pre>\nTo compile this as a mixed-mode module targeting .NET Core 3.1 you need the following settings in the project properties:<\/p>\n
- \n
- .NET Core Runtime Support (\/clr:netcore)<\/strong> for Common Language Runtime Support<\/em><\/li>\n
- netcoreapp3.1<\/strong> for .NET Core Target Framework<\/em><\/li>\n<\/ul>\n
You can see these settings in the image below:
\n![\"\"](\"https:\/\/mariusbancila.ro\/blog\/wp-content\/uploads\/2019\/12\/cppclicore1.png\")
<\/p>\nConsuming the mixed-mode component from a native application<\/h3>\n
To consume the exported Widget<\/tt> class that is using the C++\/CLI Display<\/tt> class, we can create a C++ Console application with the following code (of course, you need to properly setup the additional include directories and additional library directories so it can locate the headers and .lib file).<\/p>\n
#include \"Widget.h\"\r\n\r\nint main()\r\n{\r\n Widget widget;\r\n widget.WriteText(\"Hello, world!\");\r\n}<\/pre>\nAlthough this compiles without errors, when you run it, you get the following exception:
\n![\"\"](\"https:\/\/mariusbancila.ro\/blog\/wp-content\/uploads\/2019\/12\/cppclicore2.png\")
<\/p>\nThe reason for this is that .NET Core requires a file called <appname>.runtimeconfig.json<\/em> to accompany every .NET Core module. This file is used to define required shared frameworks and runtime options. You can read more about this file here:<\/p>\n
- \n
- .NET Core run-time configuration settings<\/a><\/li>\n
- Deep-dive into .NET Core primitives, part 3: runtimeconfig.json in depth<\/a><\/li>\n<\/ul>\n
The problem is that this file, which should be called CoreClassLib.runtimeconfig.json<\/em> for our example, is not generated by Visual Studio when creating the CLR Class Library project. This is a know bug, as reported here: C++\/CLI projects do not generate .runtimeconfig.json<\/a>.<\/p>\n
We can fix this by creating the CoreClassLib.runtimeconfig.json file with the following content.<\/p>\n
{\r\n \"runtimeOptions\": {\r\n \"framework\": {\r\n \"name\": \"Microsoft.NETCore.App\",\r\n \"version\": \"3.1.0\"\r\n }\r\n }\r\n}<\/pre>\nHowever, this file must be available in the output folder. That can be done by copying it as a Post-build event.<\/p>\n
xcopy \/Y $(ProjectDir)CoreClassLib.runtimeconfig.json $(OutputPath)<\/pre>\n
After making these changes, the C++ console application works as expected.
\n![\"\"](\"https:\/\/mariusbancila.ro\/blog\/wp-content\/uploads\/2019\/12\/cppclicore3.png\")
<\/p>\nYou can get the demo application for this article from here:
\nDownload: - Deep-dive into .NET Core primitives, part 3: runtimeconfig.json in depth<\/a><\/li>\n<\/ul>\n
- netcoreapp3.1<\/strong> for .NET Core Target Framework<\/em><\/li>\n<\/ul>\n
- .NET Core Runtime Support (\/clr:netcore)<\/strong> for Common Language Runtime Support<\/em><\/li>\n