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DLLs (C++/CX)

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You can use Visual Studio to create either a standard Win32 DLL or a Windows Runtime component DLL that can be consumed by Universal Windows Platform (UWP) apps. A standard DLL that was created by using a version of Visual Studio or the Microsoft C++ compiler that's earlier than Visual Studio 2012 may not load correctly in a UWP app and may not pass the app verification test in the Microsoft Store.

Windows Runtime component DLLs

In almost all cases, when you want to create a DLL for use in a UWP app, create it as a Windows Runtime component by using the project template of that name. You can create a Windows Runtime component project for DLLs that have public or private Windows Runtime types. A Windows Runtime component can be accessed from apps that are written in any Windows Runtime-compatible language. By default, the compiler settings for a Windows Runtime component project use the /ZW switch. A .winmd file must have the same name that the root namespace has. For example, a class that's named A.B.C.MyClass can be instantiated only if it's defined in a metadata file that's named A.winmd or A.B.winmd or A.B.C.winmd. The name of the DLL is not required to match the .winmd file name.

For more information, see Creating Windows Runtime Components in C++.

To reference a third-party Windows Runtime component binary in your project

  1. Open the shortcut menu for the project that will use the DLL and then choose Properties. On the Common Properties page, choose the Add New Reference button.

  2. A Windows Runtime component consists of a DLL file and a .winmd file that contains the metadata. Typically, these files are located in the same folder. In the left pane of the Add Reference dialog box, choose the Browse button and then navigate to the location of the DLL and its .winmd file. For more information, see Extension SDKs.

Standard DLLs

You can create a standard DLL for C++ code that doesn't consume or produce public Windows Runtime types and consume it from a UWP app. Use the Dynamic-Link Library (DLL) project type when you just want to migrate an existing DLL to compile in this version of Visual Studio but not convert the code to a Windows Runtime Component project. When you use the following steps, the DLL will be deployed alongside your app executable in the .appx package.

To create a standard DLL in Visual Studio

  1. On the menu bar, choose File, New, Project, and then select the Dynamic Link Library (DLL) template.

  2. Enter a name for the project, and then choose the OK button.

  3. Add the code. Be sure to use __declspec(dllexport) for functions that you intend to export—for example, __declspec(dllexport) Add(int I, in j);

  4. Add #include winapifamily.h to include that header file from the Windows SDK for UWP apps and set the macro WINAPI_FAMILY=WINAPI_PARTITION_APP.

To reference a standard DLL project from the same solution

  1. Open the shortcut menu for the project that will use the DLL and then choose Properties. On the Common Properties page, choose the Add New Reference button.

  2. In the left pane, select Solution, and then select the appropriate check box in the right pane.

  3. In your source code files, add a #include statement for the DLL header file, as needed.

To reference a standard DLL binary

  1. Copy the DLL file, the .lib file, and the header file, and paste them in a known location—for example, in your current project folder.

  2. Open the shortcut menu for the project that will use the DLL and then choose Properties. On the Configuration Properties, Linker, Input page, add the .lib file as a dependency.

  3. In your source code files, add a #include statement for the DLL header file, as needed.

To migrate an existing Win32 DLL for UWP app compatibility

  1. Create a project of the DLL (Universal Windows) type and add your existing source code to it.

  2. Add #include winapifamily.h to include that header file from the Windows SDK for UWP apps and set the macro WINAPI_FAMILY=WINAPI_PARTITION_APP.

  3. In your source code files, add a #include statement for the DLL header file, as needed.